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JP6168642B2 - Diffraction grating and manufacturing method thereof, optical waveguide - Google Patents

Diffraction grating and manufacturing method thereof, optical waveguide Download PDF

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JP6168642B2
JP6168642B2 JP2012082527A JP2012082527A JP6168642B2 JP 6168642 B2 JP6168642 B2 JP 6168642B2 JP 2012082527 A JP2012082527 A JP 2012082527A JP 2012082527 A JP2012082527 A JP 2012082527A JP 6168642 B2 JP6168642 B2 JP 6168642B2
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polarized light
refractive index
diffraction grating
diffraction
diffraction efficiency
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JP2013210589A (en
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海老塚 昇
昇 海老塚
勝 堀
勝 堀
昌文 伊藤
昌文 伊藤
康裕 東島
康裕 東島
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Nagoya University NUC
Tokai National Higher Education and Research System NUC
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本発明は、各種光学計測機器および、自動車や航空機の計器類等のヘッドアップディスプレイ、3次元映像用ディスプレイ、省エネオフィスや省エネ住宅の外光導入等に利用される効率が高い回折格子、あるいは偏光分離機能を有する回折格子、さらには光情報処理や光コンピューティング等に利用される能動的な回折光学素子に関するものである。   The present invention relates to various optical measuring instruments, head-up displays such as automobile and aircraft instruments, three-dimensional video displays, high-efficiency diffraction gratings used for introducing external light into energy-saving offices and energy-saving houses, or polarized light The present invention relates to a diffraction grating having a separation function, and further to an active diffractive optical element used for optical information processing, optical computing, and the like.

[透過型VPH回折格子]
二光束のレーザ干渉露光によって製作され、屈折率が正弦波状に変化する厚い回折格子は、VPH(Volume Phase Holographic)と呼ばれる。ここで、波長をλ、格子の厚さをt、格子周期をΛ、平均屈折率をn=(nmax+nmin)/2としたときに
Q=2πλt /(nΛ2) ・・・(1)
で定義される回折格子のQ値がQ<1である場合に薄い回折格子、Q>10である場合に厚い回折格子に分類される。なお、nmaxとnminはそれぞれ回折格子の最大屈折率と最小屈折率である。
[Transmission type VPH diffraction grating]
A thick diffraction grating manufactured by two-beam laser interference exposure and having a refractive index changing in a sinusoidal shape is called VPH (Volume Phase Holographic). Here, when the wavelength is λ, the thickness of the grating is t, the grating period is Λ, and the average refractive index is n = (nmax + nmin) / 2.
Q = 2πλt / (nΛ 2 ) (1)
When the Q value of the diffraction grating defined by (1) is Q <1, the diffraction grating is classified as a thin diffraction grating, and when Q> 10, the diffraction grating is classified as a thick diffraction grating. Note that nmax and nmin are the maximum refractive index and the minimum refractive index of the diffraction grating, respectively.

図1のように透過型VPH回折格子1は、格子の厚さtや屈折率変調:Δn=(nmax−nmin)/2を調整して下記ブラッグの回折条件を満足させるとS偏光(電界ベクトルが格子方向に対して水平に振動する偏光成分)あるいはP偏光(電界ベクトルが格子方向に対して垂直に振動する偏光成分)のいずれかについて最大100%の回折効率を達成することが可能である。ブラッグの回折条件は、
mλ=2nΛ sin(θ) ・・・(2)
によって与えられる。ここで、mは回折次数である。また、光束が透過型VPH回折格子1に入射する面および出射する面に対して格子が垂直である場合にはブラッグ角θ=入射角=回折角、また、格子が角度α傾斜している場合には、入射角=θ+α、回折角=θ−αである。
As shown in FIG. 1, the transmissive VPH diffraction grating 1 is adjusted to S polarization (electric field vector) by adjusting the grating thickness t and refractive index modulation: Δn = (nmax−nmin) / 2 to satisfy the following Bragg diffraction conditions. It is possible to achieve a diffraction efficiency of up to 100% for either a polarization component that oscillates horizontally relative to the grating direction) or a P-polarized light (a polarization component whose electric field vector oscillates perpendicular to the grating direction). . Bragg's diffraction conditions are
mλ = 2nΛ sin (θ) (2)
Given by. Here, m is the diffraction order. Further, when the grating is perpendicular to the surface on which the light beam enters and exits the transmission type VPH diffraction grating 1, the Bragg angle θ = incidence angle = diffraction angle, and the grating is inclined at an angle α. Are incident angle = θ + α and diffraction angle = θ−α.

VPH回折格子等の屈折率が正弦波状に変化する厚い回折格子は、0次回折光と1次回折光の結合のみを扱う2波結合解析法により、0次回折光と1次回折光の偏光回折効率特性の相対値(S偏光およびP偏光の極大値が常に100%になる)を見積ることができる。非特許文献1や非特許文献2によれば、格子が入射する面および出射する面に対して垂直な透過型VPH回折格子1に入射した光束が上記ブラッグの回折条件を満足する場合に式(2)に格子周期Λと波長λ、平均屈折率nを代入してブラッグ角θを求め、最大屈折率nmaxと最小屈折率nmin、格子の厚さtが与えられると、1次回折光のS偏光に対する回折効率ηSおよび、P偏光に対する回折効率ηPはそれぞれ、   A thick diffraction grating such as a VPH diffraction grating whose refractive index changes in a sinusoidal shape is obtained by using a two-wave coupling analysis method that handles only the combination of the 0th-order diffracted light and the 1st-order diffracted light. The relative value (the maximum value of S-polarized light and P-polarized light is always 100%) can be estimated. According to Non-Patent Document 1 and Non-Patent Document 2, when the light beam incident on the transmission type VPH diffraction grating 1 perpendicular to the surface on which the grating enters and the surface on which the light exits satisfies the Bragg diffraction condition, The Bragg angle θ is obtained by substituting the grating period Λ, wavelength λ, and average refractive index n into 2), and given the maximum refractive index nmax, minimum refractive index nmin, and grating thickness t, the S-polarized light of the first-order diffracted light The diffraction efficiency ηS for P and the diffraction efficiency ηP for P-polarized light are respectively

Figure 0006168642
Figure 0006168642

Figure 0006168642
によって求めることができる。
Figure 0006168642
Can be obtained.

透過型VPH回折格子1は、たとえば日本ペイント製のホログラム樹脂20によって作製される。日本ペイント製のホログラム樹脂20は可視光および紫外線によって重合する屈折率が高い樹脂のモノマー(RPM: Radically polymerized monomer)と紫外線によって重合する屈折率が低い樹脂のモノマー(CPM: Cationically polymerized monomer)、色素、光開始剤、溶剤等が含まれており、図1のように基板30と基板40との間に厚さtを調整するためのスペーサとしてガラスビーズ(図示しない)等を混入したホログラム樹脂20を挟み、可視光レーザの干渉露光によって干渉縞の明部のRPMが重合すると明部と暗部との間でCPMとRPMの濃度勾配が生じるため、それを解消するように明部から暗部にCPMが移動し、暗部から明部にRPMが移動する。その後、均質な紫外線照射を行うことによって残ったRPMとCPMが重合して屈折率変調が定着される。すなわち、このホログラム樹脂20の現像と定着は乾式工程である。厚いホログラムの記録材料として他にも重クロム酸ゼラチン等が利用される。重クロム酸ゼラチンの現像と定着(漂白)は湿式工程である。   The transmissive VPH diffraction grating 1 is made of, for example, a hologram resin 20 made by Nippon Paint. Nippon Paint's hologram resin 20 is a resin monomer (RPM) that is highly refractive index polymerized by visible light and ultraviolet light, a monomer monomer (CPM: Cationically polymerized monomer) that is polymerized by UV light and a low refractive index. , A photoinitiator, a solvent, and the like, and a hologram resin 20 in which glass beads (not shown) or the like are mixed as a spacer for adjusting the thickness t between the substrate 30 and the substrate 40 as shown in FIG. When the RPM of the bright part of the interference fringe is overlapped by the interference exposure of the visible light laser, a CPM and RPM density gradient is generated between the bright part and the dark part. And the RPM moves from the dark part to the bright part. Thereafter, the remaining RPM and CPM are polymerized by performing uniform ultraviolet irradiation, and the refractive index modulation is fixed. That is, development and fixing of the hologram resin 20 are dry processes. In addition, dichromated gelatin or the like is used as a thick hologram recording material. Development and fixing (bleaching) of dichromated gelatin is a wet process.

図2は上記ホログラム樹脂20によって製作された、格子周期Λ=0.984μm、平均屈折率n=1.53の透過型VPH回折格子1の波長λ=0.96、1.02、1.11μm、すなわち式(2)よりブラッグ角がそれぞれ、θ=18.6°、19.8°、21.6°における偏光回折効率の波長特性の実測値である。格子の厚さがt=20μmであることから、図2の3波長のブラッグ角における偏光回折効率特性から式(3)と式(4)を満足するような、もっともらしい屈折率変調量:Δn=(nmax−nmin)/2=0.017が求められた。図3は、図2の透過型VPH回折格子1のλ=1.02μm(θ=19.8°)における厚さに対する偏光回折効率の数値計算を示した図である。図3に示すように、この透過型VPH回折格子1は式(3)よりt=23.8μmにおいてS偏光の回折効率が最大であり、式(4)よりt=31.4μmにおいてP偏光の回折効率が最大であり、S偏光の回折効率とP偏光の回折効率の平均がt=26.6μmにおいて最大値の96%であることがわかる。   FIG. 2 shows the wavelength λ = 0.96, 1.02, 1.11 μm of the transmissive VPH diffraction grating 1 manufactured using the hologram resin 20 and having a grating period Λ = 0.984 μm and an average refractive index n = 1.53. That is, from equation (2), the Bragg angles are measured values of the wavelength characteristics of the polarization diffraction efficiency at θ = 18.6 °, 19.8 °, and 21.6 °, respectively. Since the thickness of the grating is t = 20 μm, a plausible refractive index modulation amount Δn that satisfies the expressions (3) and (4) from the polarization diffraction efficiency characteristics at the Bragg angles of three wavelengths in FIG. = (Nmax-nmin) /2=0.17 was obtained. FIG. 3 is a diagram showing numerical calculation of polarization diffraction efficiency with respect to the thickness of the transmission type VPH diffraction grating 1 of FIG. 2 at λ = 1.02 μm (θ = 19.8 °). As shown in FIG. 3, this transmission type VPH diffraction grating 1 has the maximum diffraction efficiency of S-polarized light at t = 23.8 μm from the equation (3), and P-polarized light at t = 31.4 μm from the equation (4). It can be seen that the diffraction efficiency is maximum, and the average of the diffraction efficiency of S polarization and that of P polarization is 96% of the maximum value at t = 26.6 μm.

非特許文献3によれば、透過型VPH回折格子1の内部におけるブラッグ角がθ=30°である場合には、式(3)と式(4)より、図4のようにP偏光の回折効率が最初に極大になる厚さにおいてS偏光の回折効率が0%になるような条件(ディクソンの条件1)、すなわち、偏光分離素子であることが示されている。図4の透過型VPH回折格子1は格子周期:Λ=0.4μm、波長:λ=0.6μm、平均屈折率:n=1.5、屈折率変調量:Δn=0.07、θ=30°である。スネルの屈折式:n×sinθ=sinθ0より、真空中におけるブラッグ角はθ0=48.6°である。なお、図4においてS偏光の第一極大近傍に見られるS偏光とP偏光の回折効率の平均値の極大は79%である。さらに、θ=35.3°の場合には、式(3)と式(4)より、図5のようにP偏光の回折効率が最初の極大の厚さにおいてS偏光の回折効率が第二極大となるために、S偏光とP偏光いずれも最大100%の高い回折効率を達成できる条件(ディクソンの条件2)であることが示されている。ただし、透過型VPH回折格子1は厚さが厚くなるのに従って波長帯域幅が狭くなってしまうために、S偏光の第二極大の厚さにおける波長帯域幅はS偏光の第一極大の厚さの波長帯域幅の1/3である。図5の透過型VPH回折格子1はΛ=0.346μm、λ=0.6μm、n=1.5、Δn=0.07、θ=35.3°(θ0=60°)である。なお、図5においてS偏光の第一極大近傍に見られるS偏光とP偏光の回折効率の平均値の極大は63.5%である。   According to Non-Patent Document 3, when the Bragg angle inside the transmissive VPH diffraction grating 1 is θ = 30 °, the diffraction of P-polarized light as shown in FIG. 4 from the equations (3) and (4). It is shown that the polarization separation element is a condition (Dixon's condition 1) in which the diffraction efficiency of S-polarized light becomes 0% at the thickness where the efficiency is first maximized. The transmission type VPH diffraction grating 1 of FIG. 4 has a grating period: Λ = 0.4 μm, wavelength: λ = 0.6 μm, average refractive index: n = 1.5, refractive index modulation amount: Δn = 0.07, θ = 30 °. From Snell's refraction formula: n × sin θ = sin θ0, the Bragg angle in vacuum is θ0 = 48.6 °. In FIG. 4, the maximum of the average value of the diffraction efficiencies of S-polarized light and P-polarized light seen in the vicinity of the first maximum of S-polarized light is 79%. Further, in the case of θ = 35.3 °, from the equations (3) and (4), the diffraction efficiency of the S-polarized light is the second maximum when the diffraction efficiency of the P-polarized light is the first maximum thickness as shown in FIG. In order to maximize, it is shown that both S-polarized light and P-polarized light are conditions (Dixon condition 2) that can achieve a high diffraction efficiency of 100% at the maximum. However, since the wavelength bandwidth becomes narrower as the thickness of the transmission type VPH diffraction grating 1 increases, the wavelength bandwidth at the second maximum thickness of S-polarized light is the thickness of the first maximum of S-polarized light. 1/3 of the wavelength bandwidth. The transmission type VPH diffraction grating 1 in FIG. 5 has Λ = 0.346 μm, λ = 0.6 μm, n = 1.5, Δn = 0.07, and θ = 35.3 ° (θ0 = 60 °). In FIG. 5, the maximum of the average value of the diffraction efficiency of S-polarized light and P-polarized light seen in the vicinity of the first maximum of S-polarized light is 63.5%.

[厚い透過型矩形回折格子]
厚い透過型矩形回折格子2は図6のように屈折率がn1の光学等方性媒質の基板30と、屈折率がn3の光学等方性媒質の基板40の間に断面が長方形あるいは平行四辺形である屈折率がn2aの光学等方性媒質21と屈折率がn2b(n2a≠n2b)の光学等方性媒質22が交互に設置された厚い位相型回折格子である。
[Thick transmission type rectangular diffraction grating]
As shown in FIG. 6, the thick transmission type rectangular diffraction grating 2 has a rectangular or parallel four-sided cross section between an optically isotropic medium substrate 30 having a refractive index n1 and an optically isotropic medium substrate 40 having a refractive index n3. This is a thick phase type diffraction grating in which an optically isotropic medium 21 having a refractive index n2a and an optically isotropic medium 22 having a refractive index n2b (n2a ≠ n2b) are alternately arranged.

厚い透過型矩形回折格子2は多くの場合に光学等方性媒質の基板30上に付与された光学等方性媒質の層あるいは、基板30自体をフォトリソグラフィ技術等によって光学等方性媒質21の矩形格子の畝:Ridgeが形成され、矩形格子の溝:Grooveに光学等方性媒質22が充填される。すなわち、光学等方性媒質21は基板30と同じ材質であってもよい。さらには格子の上に光学等方性媒質の基板40が設置される場合がある。なお、光学等方性媒質の基板40は光学等方性媒質22と同じ材質であってもよい。また、矩形格子の溝および基板40が空気等の気体や真空である場合には表面刻線型回折格子とも呼ばれる。   In many cases, the thick transmission type rectangular diffraction grating 2 is formed of an optically isotropic medium layer formed on the optically isotropic medium substrate 30 or the substrate 30 itself by a photolithography technique or the like. A rectangular lattice of ridges: Ridge is formed, and a groove: Groove of the rectangular lattice is filled with the optical isotropic medium 22. In other words, the optical isotropic medium 21 may be the same material as the substrate 30. Furthermore, an optically isotropic medium substrate 40 may be provided on the grating. The substrate 40 of the optical isotropic medium may be the same material as the optical isotropic medium 22. Also, when the grooves of the rectangular grating and the substrate 40 are a gas such as air or a vacuum, it is also called a surface engraved diffraction grating.

厚い透過型矩形回折格子2の回折効率を求める場合には、2波結合解析による数値計算では精度が不十分であり、0次回折光と1次回折光について正確な偏光回折効率を見積るためには、非特許文献4によれば厳密結合波解析法(Rigorous Coupled Wave Analysis:RCWA)等を用いた、例えば−3次回折光から4次回折光までの8波程度の数値計算が必要である。ただし、格子周期Λと格子の畝あるいは溝の幅の比(デューティ比)が2:1、すなわち光学等方性媒質21と光学等方性媒質22の幅が等しい厚い透過型矩形回折格子2と透過型VPH回折格子1の偏光回折効率特性は類似しており、いずれの回折格子も図3〜5のように厚さに対してS偏光とP偏光の回折効率が極大と極小を周期的に繰り返す。非特許文献5によれば、厚い透過型矩形回折格子2は使用波長λと格子周期Λが与えられた場合に、光学等方性媒質21の屈折率n2aと光学等方性媒質22の屈折率n2bおよび格子の厚さtを調整して、上記ブラッグの回折条件を満足させることによってS偏光あるいはP偏光のいずれかについて最大100%の回折効率を達成することが可能である。ただし、デューティ比が2:1の厚い透過型矩形回折格子2の格子の厚さtに対する回折効率の周期と使用波長λや格子周期Λ、最大屈折率、最小屈折率が等しい透過型VPH回折格子1の上記回折効率の周期とは、ブラッグ角θが大きくなるほど乖離する。   When calculating the diffraction efficiency of the thick transmissive rectangular diffraction grating 2, the numerical calculation by the two-wave coupling analysis is insufficient in accuracy, and in order to estimate the accurate polarization diffraction efficiency for the 0th-order diffracted light and the 1st-order diffracted light, According to Non-Patent Document 4, numerical calculation of, for example, about 8 waves from -3rd order diffracted light to 4th order diffracted light using a strictly coupled wave analysis (RCWA) or the like is necessary. However, the ratio of the grating period Λ to the width of the groove or groove (duty ratio) is 2: 1, that is, the thick transmission type rectangular diffraction grating 2 in which the optical isotropic medium 21 and the optical isotropic medium 22 are equal in width. The polarization diffraction efficiency characteristics of the transmissive VPH diffraction grating 1 are similar. As shown in FIGS. 3 to 5, the diffraction efficiency of the S-polarized light and the P-polarized light is periodically maximized and minimized with respect to the thickness. repeat. According to Non-Patent Document 5, the thick transmission type rectangular diffraction grating 2 is provided with a refractive index n2a of the optical isotropic medium 21 and a refractive index of the optical isotropic medium 22 when a use wavelength λ and a grating period Λ are given. By adjusting n2b and the grating thickness t to satisfy the Bragg diffraction conditions, it is possible to achieve a diffraction efficiency of up to 100% for either S-polarized light or P-polarized light. However, the transmission type VPH diffraction grating in which the period of diffraction efficiency with respect to the grating thickness t of the thick transmission type rectangular diffraction grating 2 having a duty ratio of 2: 1 and the operating wavelength λ, the grating period Λ, the maximum refractive index, and the minimum refractive index are equal. The period of the diffraction efficiency of 1 becomes more dissimilar as the Bragg angle θ increases.

光学等方性媒質21の屈折率:n2a=1.7であり、光学等方性媒質22の屈折率:n2b=1.5であり、デューティ比が2:1の厚い透過型矩形回折格子2について、波長λと格子周期Λが等しい、すなわち式(2)より真空中におけるブラッグ角がθ0=30°の場合に、1次回折光の回折効率が最初に最大になる格子周期で規格化された厚さ:t/Λを上記RCWA法によって求めた場合にはS偏光がt/Λ=1.80、P偏光がt/Λ=2.30である。一方、最大屈折率:nmax=1.7であり、最小屈折率:nmin=1.5である透過型VPH回折格子1(つまり、透過型矩形回折格子1の最大屈折率は、透過型矩形回折格子2の光学等方性媒質21、22の屈折率のうち大きい方で、最小屈折率は光学等方性媒質21、22の屈折率のうち小さい方)についてθ0=30°の場合に式(3)および式(4)によって1次回折光の回折効率を求めると、S偏光がt/Λ=2.38であり、P偏光がt/Λ=2.95である。従って、厚い透過型矩形回折格子2と透過型VPH回折格子1の厚さの比はS偏光とP偏光について、それぞれ1:1.32と1:1.28である。   Thick transmissive rectangular diffraction grating 2 in which the refractive index of the optical isotropic medium 21 is n2a = 1.7, the refractive index of the optical isotropic medium 22 is n2b = 1.5, and the duty ratio is 2: 1. Is equal to the grating period at which the diffraction efficiency of the first-order diffracted light is first maximized when the wavelength λ is equal to the grating period Λ, that is, when the Bragg angle in vacuum is θ0 = 30 °. When the thickness: t / Λ is obtained by the RCWA method, t / Λ = 1.80 for S-polarized light and t / Λ = 2.30 for P-polarized light. On the other hand, the transmissive VPH diffraction grating 1 having a maximum refractive index: nmax = 1.7 and a minimum refractive index: nmin = 1.5 (that is, the maximum refractive index of the transmissive rectangular diffraction grating 1 is transmissive rectangular diffraction). When θ0 = 30 ° with respect to the larger one of the refractive indexes of the optically isotropic media 21 and 22 of the grating 2 and the smaller one of the refractive indexes of the optically isotropic media 21 and 22, the formula ( When the diffraction efficiency of the first-order diffracted light is obtained by 3) and Equation (4), the S-polarized light is t / Λ = 2.38 and the P-polarized light is t / Λ = 2.95. Therefore, the ratio of the thicknesses of the thick transmissive rectangular diffraction grating 2 and the transmissive VPH diffraction grating 1 is 1: 1.32 and 1: 1.28 for S-polarized light and P-polarized light, respectively.

特許文献1によれば、表面刻線型の厚い透過型矩形回折格子2についてデューティ比と格子の畝の屈折率を調整することによって、任意のブラッグ角θに対して、一方の偏光の回折効率が極大になる厚さにおいて、もう一方の偏光の回折効率が0%になる条件が数値計算によって示されている。また、非特許文献6によれば、表面刻線型の厚い透過型矩形回折格子2についてデューティ比と格子の畝の屈折率を調整することによって、任意の入射角および回折角に対して、S偏光とP偏光の効率の波長特性を近づけてS偏光とP偏光を同時、すなわち自然偏光や円偏光、45°直線偏光等に対して100%に近い高い回折効率を達成できることが数値計算によって示されている。厚い透過型矩形回折格子2の光学等方性媒質21の屈折率:n2a=1.4であり、光学等方性媒質22の屈折率:n2b=1.0である表面刻線型の厚い透過型矩形回折格子2について、非特許文献6によると、使用波長λと格子周期Λが等しい、すなわち式(2)より真空中におけるブラッグ角がθ0=30°の場合に、(22)のデューティ比が概ね10:3であり、t/Λ=3.1である条件において自然偏光等に対して97%程度の高い回折効率を達成できると見積られている。この時、厚さtと光学等方性媒質22の幅w2のアスペクト比は10.3:1である。   According to Patent Document 1, by adjusting the duty ratio and the refractive index of the grating ridge for a thick surface-transmitted rectangular diffraction grating 2, the diffraction efficiency of one polarized light can be obtained for an arbitrary Bragg angle θ. The numerical calculation shows the condition that the diffraction efficiency of the other polarized light becomes 0% at the maximum thickness. Further, according to Non-Patent Document 6, by adjusting the duty ratio and the refractive index of the grating ridge in the surface-transmitted thick transmission rectangular diffraction grating 2, the S-polarized light can be obtained for any incident angle and diffraction angle. Numerical calculations show that high wavelength efficiency close to 100% can be achieved for S polarization and P polarization simultaneously, that is, natural polarization, circular polarization, 45 ° linear polarization, etc. ing. Thick transmissive rectangular diffraction grating 2 has a refractive index of optical isotropic medium 21: n2a = 1.4 and a refractive index of optical isotropic medium 22: n2b = 1.0. Regarding the rectangular diffraction grating 2, according to Non-Patent Document 6, when the operating wavelength λ is equal to the grating period Λ, that is, when the Bragg angle in vacuum is θ0 = 30 °, the duty ratio of (22) is It is estimated that a high diffraction efficiency of about 97% can be achieved with respect to natural polarized light or the like under the condition of approximately 10: 3 and t / Λ = 3.1. At this time, the aspect ratio of the thickness t and the width w2 of the optical isotropic medium 22 is 10.3: 1.

特許文献2および特許文献3によれば、偏光分離素子は厚い透過型矩形回折格子2の光学等方性媒質21の代わりに光学異方性媒質を使用して、入射光束に対してS偏光あるいはP偏光の屈折率を格子の溝に充填される光学等方性材質22の屈折率n2bと一致させ、もう一方の偏光が光学等方性媒質22の屈折率n2bと異なるようにすることによって、0次以外の回折光についてS偏光あるいはP偏光のみを利用する回折光学素子について記述されている。   According to Patent Document 2 and Patent Document 3, the polarization separating element uses an optically anisotropic medium instead of the optically isotropic medium 21 of the thick transmission type rectangular diffraction grating 2, so By making the refractive index of the P-polarized light coincide with the refractive index n2b of the optical isotropic material 22 filled in the grooves of the grating, and making the other polarized light different from the refractive index n2b of the optical isotropic medium 22, A diffractive optical element that uses only S-polarized light or P-polarized light for diffracted light other than the 0th order is described.

非特許文献7によれば、図6のような厚い矩形回折格子の溝に液晶を充填して、無電界において入射光束に対して光学等方性媒質21の屈折率n2aと光学異方性媒質である液晶の屈折率とを一致させておく。厚い矩形回折格子の光束が入射する面と出射する面に配置された透明電極によって格子に電圧を印可して液晶の屈折率を変化させることによって、素通しの窓から回折格子に切り替える機能性回折光学素子について記述されている。ただし、無電界でも電圧を印可した場合であってもS偏光とP偏光に対する屈折率や回折効率の異方性についての記述は見当たらない。   According to Non-Patent Document 7, a groove of a thick rectangular diffraction grating as shown in FIG. 6 is filled with liquid crystal, and the refractive index n2a of the optical isotropic medium 21 and the optically anisotropic medium with respect to the incident light beam without an electric field. The refractive index of the liquid crystal is matched. Functional diffractive optics that switches from a transparent window to a diffraction grating by applying a voltage to the grating and changing the refractive index of the liquid crystal by means of transparent electrodes placed on the light incident and exit surfaces of a thick rectangular diffraction grating The device is described. However, there is no description about the refractive index and diffraction efficiency anisotropy for S-polarized light and P-polarized light even when no voltage is applied.

特開2004−198641号公報JP 2004-198641 A 特開2000−75130号公報JP 2000-75130 A 特開2005−55773号公報JP 2005-55773 A 特開2006−201388号公報JP 2006-201388 A

H. Kogelnik, “Coupled Wave Theory for Thick Hologram Grating”, Bell System Technical Journal, 48, 2909-2946, 1969.H. Kogelnik, “Coupled Wave Theory for Thick Hologram Grating”, Bell System Technical Journal, 48, 2909-2946, 1969. I. K. Baldry, J. Bland-Hawthorn,J.G.Robertson, “Volume Phase Holographic gratings: Polarization properties and Diffraction Efficiency”, Publ. Astron. Soc. Pacific 116, 403-414, 2004.I. K. Baldry, J. Bland-Hawthorn, J.G. Robertson, “Volume Phase Holographic gratings: Polarization properties and Diffraction Efficiency”, Publ. Astron. Soc. Pacific 116, 403-414, 2004. L. D. Dickson, R. D. Rallison, B. H. Yung, “Holographic polarization-separation elements”, Appl. Opt. 33, 5378-5385, 1994.L. D. Dickson, R. D. Rallison, B. H. Yung, “Holographic polarization-separation elements”, Appl. Opt. 33, 5378-5385, 1994. N. Chateau, J. Hugonin, “Algorithm for the rigorous coupled-wave analysis of grating diffraction”, J. Opt. Soc. Am. A, 11,1321-1331, 1994.N. Chateau, J. Hugonin, “Algorithm for the rigorous coupled-wave analysis of grating diffraction”, J. Opt. Soc. Am. A, 11,1321-1331, 1994. M. C. Gupta, S. T. Peng,“Diffraction characteristics of surface-relief gratings”,Appl. Opt., 32, 2911-2917, 1993.M. C. Gupta, S. T. Peng, “Diffraction characteristics of surface-relief gratings”, Appl. Opt., 32, 2911-2917, 1993. H. J. Gerritsen, M. L. Jepsen, “Rectangular Surface-Relief Transmission Gratings with a Very Large First-Order Diffraction Efficiency (95%) for Unpolarized Light”, Appl. Opt., 37, 5823-5829, 1998.H. J. Gerritsen, M. L. Jepsen, “Rectangular Surface-Relief Transmission Gratings with a Very Large First-Order Diffraction Efficiency (95%) for Unpolarized Light”, Appl. Opt., 37, 5823-5829, 1998. M. L. Jepsen, H. J. Gerritsen, “Liquide-crystal-filled gratings with high diffraction efficiency”, Opt. L., 21, 1081-1083, 1996.M. L. Jepsen, H. J. Gerritsen, “Liquide-crystal-filled gratings with high diffraction efficiency”, Opt. L., 21, 1081-1083, 1996. N. Ebizuka, M. Iye, T. Sasaki, “Optically Anisotropic Crystalline Grisms or Astronomical Spectrographs”, Appl. Opt., 37, 1236-1242, 1998.N. Ebizuka, M. Iye, T. Sasaki, “Optically Anisotropic Crystalline Grisms or Astronomical Spectrographs”, Appl. Opt., 37, 1236-1242, 1998.

解決しようとする問題点は、透過型VPH回折格子1はブラッグ角θが大きくなるのに従いS偏光とP偏光の回折効率特性が乖離することである。透過型VPH回折格子1の真空中のブラッグ角がθ0=45°、すなわち光軸を直角に折曲げる場合に、格子の平均屈折率がn=1.41において図4のような上記ディクソンの条件1の偏光回折効率特性であるために自然偏光等に対する回折効率は最大79%程度である。格子の平均屈折率nをより大きくすることにより自然偏光等に対する回折効率を向上できるが、現状で入手可能なホログラム記録材料の平均屈折率nは最大1.55程度であるために、自然偏光等に対する回折効率が最大85%程度であることが問題である。また、透過型VPH回折格子1は上記ディクソンの条件2において自然偏光等に対して最大100%の高い回折効率を達成することが可能であるが、平均屈折率nによってθ0が限定されてしまう上に、格子の厚さtが厚くなることにより回折効率特性の半値幅が狭くなることが問題である。   The problem to be solved is that the diffractive efficiency characteristics of the S-polarized light and the P-polarized light deviate as the Bragg angle θ increases in the transmissive VPH diffraction grating 1. When the Bragg angle in vacuum of the transmission type VPH diffraction grating 1 is θ0 = 45 °, that is, when the optical axis is bent at a right angle, the average refractive index of the grating is n = 1.41. The diffraction efficiency with respect to natural polarized light or the like is about 79% at maximum because of the polarization diffraction efficiency characteristic of 1. Although the diffraction efficiency for natural polarized light and the like can be improved by increasing the average refractive index n of the grating, the average refractive index n of the currently available hologram recording material is about 1.55 at the maximum, so The problem is that the diffraction efficiency with respect to the maximum is about 85%. Further, the transmission type VPH diffraction grating 1 can achieve a high diffraction efficiency of up to 100% with respect to natural polarization or the like under the above-mentioned Dixon condition 2, but θ0 is limited by the average refractive index n. In addition, there is a problem that the full width at half maximum of the diffraction efficiency characteristic becomes narrow as the grating thickness t increases.

厚い透過型矩形回折格子2は前述のように光学等方性媒質21と光学等方性媒質22の屈折率の比と幅を調整することにより、S偏光とP偏光の回折効率特性を近づけることができる。しかし、RCWAの数値計算によると、光学等方性媒質21の屈折率n2aと光学等方性媒質22の屈折率n2bの比が小さくなるほど、あるいはブラッグ角θが大きくなるほど、屈折率が低い媒質の幅が狭くなり、格子の厚さtが厚くなるために、屈折率が低い媒質の幅と厚さtのアスペクト比が大きくなり、屈折率が低い媒質を注入する溝の加工が困難になってしまうことが問題である。非特許文献6によると、光学等方性媒質21の屈折率:n2a=1.4であり、光学等方性媒質22の屈折率:n2b=1.0である表面刻線型の厚い透過型矩形回折格子2は真空中のブラッグ角がθ0=45°の場合に、格子周期Λと光学等方性媒質22の幅w2のデューティ比がΛ:w2=20:3程度であり、t/Λ=4.2である条件において自然偏光等に対して約98%の高い回折効率を達成できると見積られている。しかし、光学等方性媒質22の溝のアスペクト比がt:w2=28:1であるため、ドライエッチング等による光学等方性媒質22の溝の加工が困難である。   The thick transmission type rectangular diffraction grating 2 adjusts the refractive index ratio and the width of the optical isotropic medium 21 and the optical isotropic medium 22 as described above, thereby bringing the diffraction efficiency characteristics of S-polarized light and P-polarized light closer to each other. Can do. However, according to the numerical calculation of RCWA, the smaller the ratio of the refractive index n2a of the optical isotropic medium 21 and the refractive index n2b of the optical isotropic medium 22, or the larger the Bragg angle θ, the lower the refractive index of the medium. Since the width becomes narrower and the grating thickness t becomes thicker, the aspect ratio between the width of the medium having a low refractive index and the thickness t becomes large, making it difficult to process a groove for injecting a medium having a low refractive index. Is a problem. According to Non-Patent Document 6, the refractive index of the optical isotropic medium 21 is n2a = 1.4, and the refractive index of the optical isotropic medium 22 is n2b = 1.0. In the diffraction grating 2, when the Bragg angle in vacuum is θ0 = 45 °, the duty ratio of the grating period Λ and the width w2 of the optical isotropic medium 22 is about Λ: w2 = 20: 3, and t / Λ = It is estimated that high diffraction efficiency of about 98% can be achieved with respect to natural polarized light or the like under the condition of 4.2. However, since the aspect ratio of the groove of the optical isotropic medium 22 is t: w2 = 28: 1, it is difficult to process the groove of the optical isotropic medium 22 by dry etching or the like.

請求項1に記載の回折格子は、屈折率が正弦波状に変調された格子構造である透過型VPH回折格子であって、光学異方性媒質を用い、所望の波長、および所望のブラッグ角に対して、S偏光に対する最大屈折率をnSmax、最小屈折率をnSmin、P偏光に対する最大屈折率をnPmax、最小屈折率をnPminとして、
nSmax、nSmin、nPmax、およびnPminは、
(nSmax−nSmin)/cosθSと、(nPmax−nPmin)*cos2θP/cosθPとが、10%以内の違いとなるように、それらの値が設定され、これにより、S偏光の回折効率の厚さ依存特性における周期と、P偏光の回折効率の厚さ依存特性における周期との差が10%以内となるように一致させ、さらに、回折格子の厚さは、上記設定されたS偏光の回折効率の厚さ依存特性、およびP偏光の回折効率の厚さ依存特性に基づき、S偏光の回折効率とP偏光の回折効率の平均が90%以上となるように設定されている、ことを特徴とする。
ただし、上記式においてθSはS偏光に対するブラッグ角、θPはP偏光に対するブラッグ角である。
つまり、光学異方性媒質のS偏光に対する最大屈折率と最小屈折率との差、およびP偏光に対する最大屈折率と最小屈折率との差、および格子の厚さtの3つの制御によって、任意の波長λおよび任意の格子周期Λ、すなわち任意のブラッグ角θにおいてS偏光とP偏光の回折効率を所望の分光特性に制御したことを主要な特徴とする。上記差に替えて、S偏光に対する屈折率変調量(最大屈折率と最小屈折率との差の二分の一)、およびP偏光に対する屈折率変調量、および格子の厚さtの3つを制御するのも、同様である。
The diffraction grating according to claim 1 is a transmission type VPH diffraction grating having a grating structure in which a refractive index is modulated in a sine wave shape, using an optically anisotropic medium, and having a desired wavelength and a desired Bragg angle. In contrast, the maximum refractive index for S-polarized light is nSmax, the minimum refractive index is nSmin, the maximum refractive index for P-polarized light is nPmax, and the minimum refractive index is nPmin.
nSmax, nSmin, nPmax, and nPmin are
(NSmax−nSmin) / cos θS and (nPmax−nPmin) * cos 2θP / cos θP are set so that the difference is within 10%, and thereby the thickness dependence of the diffraction efficiency of S-polarized light and the period in the characteristic, the difference between the period in the thickness dependence of the diffraction efficiency of the P-polarized light are matched to be within 10%, further, the thickness of the diffraction grating, the diffraction efficiency of the set S polarized light thickness dependent properties, and on the basis of the thickness dependence of the diffraction efficiency of the P-polarized light, the average of the diffraction efficiency and the diffraction efficiency of the P polarized light of S-polarized light is set to be 90% or more, characterized in that .
In the above equation, θS is the Bragg angle for S-polarized light, and θP is the Bragg angle for P-polarized light.
In other words, it is possible to arbitrarily control the difference between the maximum refractive index and the minimum refractive index for the S-polarized light of the optically anisotropic medium, the difference between the maximum refractive index and the minimum refractive index for the P-polarized light, and the thickness t of the grating. The main characteristic is that the diffraction efficiencies of the S-polarized light and the P-polarized light are controlled to the desired spectral characteristics at the wavelength λ and the arbitrary grating period Λ, that is, the arbitrary Bragg angle θ. In place of the above difference, the refractive index modulation amount for S-polarized light (one half of the difference between the maximum refractive index and the minimum refractive index), the refractive index modulation amount for P-polarized light, and the thickness t of the grating are controlled. The same applies to the above.

つまり、本発明の回折格子は、請求項1に記載の回折格子において、S偏光に対する最大屈折率をnSmax、最小屈折率をnSmin、P偏光に対する最大屈折率をnPmax、最小屈折率をnPminとして、nSmax、nSmin、nPmax、およびnPminは、
(nSmax−nSmin)/cosθS=(nPmax−nPmin)*cos2θP/cosθP
を満たす値とすることで、S偏光の回折効率およびP偏光の回折効率の平均を、所望の波長、入射角において90%以上としたことを特徴とする。さらには95%以上、あるいは99%以上とすることも可能である。
ただし、上記式においてθSはS偏光に対するブラッグ角、θPはP偏光に対するブラッグ角である。
That is, the diffraction grating of the present invention is the diffraction grating according to claim 1, wherein the maximum refractive index for S-polarized light is nSmax, the minimum refractive index is nSmin, the maximum refractive index for P-polarized light is nPmax, and the minimum refractive index is nPmin. nSmax, nSmin, nPmax, and nPmin are
(NSmax−nSmin) / cos θS = (nPmax−nPmin) * cos 2θP / cos θP
By satisfying the above condition, the average of the diffraction efficiency of S-polarized light and the diffraction efficiency of P-polarized light is set to 90% or more at a desired wavelength and incident angle. Further, it can be 95% or more, or 99% or more.
In the above equation, θS is the Bragg angle for S-polarized light, and θP is the Bragg angle for P-polarized light.

また、本発明の回折格子は、請求項1とは別の回折格子において、S偏光に対する最大屈折率をnSmax、最小屈折率をnSmin、P偏光に対する最大屈折率をnPmax、最小屈折率をnPminとして、nSmax、nSmin、nPmax、およびnPminは、
(nSmax−nSmin)/cosθS=2(nPmax−nPmin)*cos2θP/cosθP
または、
2(nSmax−nSmin)/cosθS=(nPmax−nPmin)*cos2θP/cosθP
を満たす値とすることで、S偏光およびP偏光の回折効率のうち、一方を90%以上、他方を1%以下としたことを特徴とする。一方の回折効率を95%以上、あるいは99%以上とすることも可能である。
ただし、上記式においてθSはS偏光に対するブラッグ角、θPはP偏光に対するブラッグ角である。
The diffraction grating of the present invention is a diffraction grating different from that of claim 1, wherein the maximum refractive index for S-polarized light is nSmax, the minimum refractive index is nSmin, the maximum refractive index for P-polarized light is nPmax, and the minimum refractive index is nPmin. , NSmax, nSmin, nPmax, and nPmin are
(NSmax−nSmin) / cos θS = 2 (nPmax−nPmin) * cos 2θP / cos θP
Or
2 (nSmax−nSmin) / cos θS = (nPmax−nPmin) * cos 2θP / cos θP
By setting the value to satisfy the above, one of the diffraction efficiencies of S-polarized light and P-polarized light is set to 90% or more and the other is set to 1% or less. One diffraction efficiency can be 95% or more, or 99% or more.
In the above equation, θS is the Bragg angle for S-polarized light, and θP is the Bragg angle for P-polarized light.

また、請求項1に記載の回折格子は、以下のような構成とすることができる。
1つは、光学等方性の樹脂に、所定の方向に配向した一軸性あるいは二軸性光学異方性の液晶が混合された樹脂であり、樹脂中の液晶の濃度によって屈折率が正弦波状に変調され、液晶の濃度および液晶分子の配向方向によって、S偏光に対する最大屈折率と最小屈折率との差と、P偏光に対する最大屈折率と最小屈折率との差とを、異なる所定値としたことを特徴とする回折格子である。
他の1つは、二軸性光学異方性の液晶と、液晶を挟んでその液晶に接し、液晶を所定の方向に配向させる液晶配向膜と、液晶を挟む1対の電極が周期的に配置された電極部と、を有し、電極部への電圧の印加によって液晶分子の配向方向を制御することにより、液晶の屈折率を正弦波状に変調し、かつ、S偏光に対する最大屈折率と最小屈折率との差と、P偏光に対する最大屈折率と最小屈折率との差とを異なる所定値とし、電極部への印加電圧値を変えることで、S偏光の回折効率とP偏光の回折効率とを可変としたことを特徴とする回折格子である。
Moreover, the diffraction grating of Claim 1 can be set as the following structures.
One is a resin in which uniaxial or biaxial optically anisotropic liquid crystal oriented in a predetermined direction is mixed with an optically isotropic resin, and the refractive index is sinusoidal depending on the concentration of the liquid crystal in the resin. The difference between the maximum refractive index and the minimum refractive index for the S-polarized light and the difference between the maximum refractive index and the minimum refractive index for the P-polarized light are different from each other according to the concentration of the liquid crystal and the orientation direction of the liquid crystal molecules. This is a diffraction grating characterized by the above.
The other is that a biaxial optically anisotropic liquid crystal, a liquid crystal alignment film that contacts the liquid crystal with the liquid crystal sandwiched therebetween, and aligns the liquid crystal in a predetermined direction, and a pair of electrodes that sandwich the liquid crystal periodically And controlling the orientation direction of the liquid crystal molecules by applying a voltage to the electrode portion, thereby modulating the refractive index of the liquid crystal in a sine wave shape, and the maximum refractive index for S-polarized light By making the difference between the minimum refractive index and the difference between the maximum refractive index and the minimum refractive index for P-polarized light different from each other and changing the voltage applied to the electrode section, the diffraction efficiency of S-polarized light and the diffraction of P-polarized light are changed. The diffraction grating is characterized in that the efficiency is variable.

請求項1に記載の回折格子は、透過型VPH回折格子において、液晶等の光学異方性媒質を使用した場合に、光学異方性媒質はS偏光に対する最大屈折率がnSmax、最小屈折率がnSmin、P偏光に対する最大屈折率がnPmax、最小屈折率がnPmin、S偏光とP偏光に対するブラッグ角がそれぞれ、θSおよびθPであるとすると、nSmax、nSmin、nPmax、およびnPminを調整することによって、   In the diffraction grating according to claim 1, when an optical anisotropic medium such as liquid crystal is used in the transmission type VPH diffraction grating, the optical anisotropic medium has a maximum refractive index of nSmax and a minimum refractive index of S-polarized light. Assuming that the maximum refractive index for nSmin and P-polarized light is nPmax, the minimum refractive index is nPmin, and the Bragg angles for S-polarized light and P-polarized light are θS and θP, respectively, by adjusting nSmax, nSmin, nPmax, and nPmin,

Figure 0006168642
Figure 0006168642

Figure 0006168642
Figure 0006168642

スネルの屈折の式より
(nSmax+nSmin) sinθS = (nPmax+nPmin) sinθP
であるから、
From Snell's equation of refraction
(nSmax + nSmin) sinθS = (nPmax + nPmin) sinθP
Because

Figure 0006168642
Figure 0006168642

を満足するようなθSとθPにおいて、式(3)と式(4)が等しくなるために、図7のようにS偏光およびP偏光の1次回折光の回折効率特性が一致する。そして、その一致した極大値において90%以上の回折効率となる。つまり、所望のブラッグ角(言い換えれば所望の格子周期Λ、波長λ)において、式(5)を満たすようS偏光に対する最大屈折率と最小屈折率との差、およびP偏光に対する最大屈折率と最小屈折率との差を制御すれば、S偏光の回折効率の特性とP偏光の回折効率の特性を一致させて、その一致した極大値においてS偏光とP偏光の回折効率の平均を90%以上とすることができる。式(5)の左辺と右辺が近似等号によって結ばれているのは、左辺と右辺が厳密に等しくなくても、多くの場合に実用上問題なく利用できるからである。左辺と右辺が10%以内の違いであれば、実用上問題ない。 Since θS and θP satisfying the above conditions, the equations (3) and (4) are equal, so that the diffraction efficiency characteristics of the first-order diffracted light of S-polarized light and P-polarized light coincide as shown in FIG. The diffraction efficiency is 90% or more at the matched maximum value. That is, in (a desired grating period lambda, the wavelength λ in other words) the desired Bragg angle, the maximum refractive index and the minimum difference between the maximum refractive index and the minimum refractive index for S-polarized light, and for P-polarized light so as to satisfy the equation (5) If the difference from the refractive index is controlled, the characteristics of the diffraction efficiency of S-polarized light and the characteristics of diffraction efficiency of P-polarized light are matched, and the average of the diffraction efficiency of S-polarized light and P-polarized light is 90% or more at the matched maximum value. It can be. The reason why the left side and the right side of Equation (5) are connected by an approximate equal sign is that in many cases, the left side and the right side can be used without any problem even if they are not exactly equal. If the difference between the left side and the right side is within 10%, there is no practical problem.

発明とは別に他の回折格子は、透過型VPH回折格子において、液晶等の光学異方性媒質を使用した場合に、光学異方性媒質はS偏光に対する最大屈折率がnSmax、最小屈折率がnSmin、P偏光に対する最大屈折率がnPmax、最小屈折率がnPmin、S偏光とP偏光に対するブラッグ角がそれぞれ、θSおよびθPであるとすると、nSmax、nSmin、nPmaxおよびnPminを調整することによって、 Apart from the invention, another diffraction grating is a transmissive VPH diffraction grating, and when an optical anisotropic medium such as liquid crystal is used, the optical anisotropic medium has a maximum refractive index of nSmax and a minimum refractive index of S-polarized light. Assuming that the maximum refractive index for nSmin and P-polarized light is nPmax, the minimum refractive index is nPmin, and the Bragg angles for S-polarized light and P-polarized light are θS and θP, respectively, by adjusting nSmax, nSmin, nPmax and nPmin,

Figure 0006168642
あるいは、
Figure 0006168642
Figure 0006168642
Or
Figure 0006168642

を満足するような任意のθSとθPにおいて、式(3)の格子の厚さtに対する周期が式(4)の格子の厚さtに対する周期の2倍あるいは1/2になり、図4に示す上記ディクソンの条件1のように、S偏光あるいはP偏光の1次回折光の効率が最初の極大になる格子の厚さtにおいて、P偏光あるいはS偏光の1次回折光の効率が0%になる偏光特性になる。つまり、所望のブラッグ角において、式(6)あるいは式(7)を満たすようS偏光に対する最大屈折率と最小屈折率との差、およびP偏光に対する最大屈折率と最小屈折率との差を制御すれば、S偏光とP偏光のうち、一方を90%以上の回折効率とし、他方を1%以下の回折効率とすることができ、偏光分離素子として機能させることができる。式(6)および式(7)の左辺と右辺が近似等号によって結ばれているのは、左辺と右辺が厳密に等しくなくても、多くの場合に実用上問題なく利用できるからである。
以上のことから、所望のブラッグ角において、S偏光に対する最大屈折率と最小屈折率との差、およびP偏光に対する最大屈折率と最小屈折率との差を制御すれば、S偏光の回折効率と、P偏光の回折効率を所望の特性とすることができることがわかる。
For any θS and θP that satisfy the above, the period for the grating thickness t in equation (3) is twice or ½ the period for the grating thickness t in equation (4). As shown in the above-mentioned Dixon condition 1, the efficiency of the first-order diffracted light of P-polarized light or S-polarized light becomes 0% at the grating thickness t at which the efficiency of the first-order diffracted light of S-polarized light or P-polarized light reaches the first maximum. It becomes polarization characteristics. That is, at a desired Bragg angle, the difference between the maximum refractive index and the minimum refractive index for S-polarized light and the difference between the maximum refractive index and the minimum refractive index for P-polarized light are controlled so as to satisfy Expression (6) or Expression (7). If so, one of the S-polarized light and the P-polarized light can have a diffraction efficiency of 90% or more, and the other can have a diffraction efficiency of 1% or less, and can function as a polarization separation element. The reason why the left side and the right side of the equations (6) and (7) are connected by the approximate equal sign is that even if the left side and the right side are not exactly equal, in many cases, they can be used without any practical problem.
From the above, if the difference between the maximum refractive index and the minimum refractive index for S-polarized light and the difference between the maximum refractive index and the minimum refractive index for P-polarized light at the desired Bragg angle is controlled, It can be seen that the diffraction efficiency of P-polarized light can be set to a desired characteristic.

請求項4に記載の回折格子は、2種類の屈折率が異なる材料が交互に周期的に配置された矩形格子構造である透過型の回折格子であって、2種類の材料のうち一方が光学異方性媒質、他方が光学等方性媒質であり、所望の波長および所望のブラッグ角に対して、光学異方性媒質のS偏光に対する最大屈折率をn2cS、P偏光に対する最大屈折率をn2cPとし、光学等方性媒質の屈折率をn2aとして、
n2a、n2cS、およびn2cPは、
n2cP>n2cS>n2aまたはn2cP<n2cS<n2aの場合には、A1*(n2cS−n2a)/cosθSと、B1*(n2cP−n2a)*cos2θP/cosθPとが、
n2cP>n2a>n2cSまたはn2cP<n2a<n2cSの場合には、A2*(n2cS−n2a)/cosθSと、−B2*(n2cP−n2a)*cos2θP/cosθPとが、10%以内の違いとなるように、それらの値が設定され、これにより、S偏光の回折効率の厚さ依存特性における周期と、P偏光の回折効率の厚さ依存特性における周期との差が10%以内となるように一致させ、
さらに、回折格子の厚さは、上記設定されたS偏光の回折効率の厚さ依存特性、およびP偏光の回折効率の厚さ依存特性に基づき、S偏光の回折効率とP偏光の回折効率の平均が90%以上となるように設定されていることを特徴とする。
ただし、上記式においてθSはS偏光に対するブラッグ角、θPはP偏光に対するブラッグ角である。また、A1、A2はRCWA法によって求めた回折格子のS偏光の回折効率の厚さ依存特性における波数(1/周期)を、2波結合解析法によって求めた透過型VPH回折格子のS偏光の回折効率の厚さ依存特性における波数(1/周期)で割った値である。また、B1B2はRCWA法によって求めた回折格子のP偏光の回折効率の厚さ依存特性における波数(1/周期)を2波結合解析法によって求めた透過型VPH回折格子のP偏光の回折効率の厚さ依存特性における波数(1/周期)で割った値である。また、上記の透過型VPH回折格子とは、S偏光に対する最大屈折率をn2cS、n2aのうち大きい方、最小屈折率をn2cS、n2aのうち小さい方とし、P偏光に対する最大屈折率をn2cP、n2aのうち大きい方、最小屈折率をn2cP、n2aのうち小さい方とした透過型VPH回折格子である。
さらには95%以上、あるいは99%以上とすることも可能である。
また、本発明の回折格子は、請求項4とは別の回折格子において、光学異方性媒質のS偏光に対する最大屈折率をn2cS、P偏光に対する最大屈折率をn2cPとし、2種類の材料のうち他方の材料の屈折率をn2aとして、n2a、n2cS、およびn2cPは、
n2cP>n2cS>n2aまたはn2cP<n2cS<n2aの場合には、2A1*(n2cS−n2a)/cosθS=B1*(n2cP−n2a)*cos2θP/cosθP、あるいは、A1*(n2cS−n2a)/cosθS=2B1*(n2cP−n2a)*cos2θP/cosθP
n2cP>n2a>n2cSまたはn2cP<n2a<n2cSの場合には、2A2*(n2cS−n2a)/cosθS=−B2*(n2cP−n2a)*cos2θP/cosθP、あるいは、A2*(n2cS−n2a)/cosθS=−2B2*(n2cP−n2a)*cos2θP/cosθPを満たす値とすることで、S偏光およびP偏光の回折効率のうち、一方を90%以上、他方を1%以下としたことを特徴とする。一方の回折効率を95%以上、あるいは99%以上とすることも可能である。
なお、上記式におけるθS、θP、A1、A2、B1、B2は、前述と同様である。
請求項4に記載の回折格子は、2種類の屈折率が異なる材料が交互に周期的に配置された格子構造である透過型の回折格子において、一方の材料として光学異方性媒質を用い、その光学異方性媒質のS偏光に対する屈折率がn2cS、P偏光に対する屈折率がn2cP、S偏光とP偏光に対するブラッグ角がそれぞれθSおよびθPであるとすると式5と同様にn2a、n2cS、およびn2cPを選ぶことによって、
The diffraction grating according to claim 4 is a transmission type diffraction grating having a rectangular grating structure in which two kinds of materials having different refractive indexes are alternately and periodically arranged, and one of the two kinds of materials is optical. An anisotropic medium, the other is an optical isotropic medium, and the maximum refractive index for S-polarized light of the optical anisotropic medium is n2cS and the maximum refractive index for P-polarized light is n2cP for a desired wavelength and a desired Bragg angle. And the refractive index of the optically isotropic medium is n2a,
n2a, n2cS, and n2cP are
In the case of n2cP>n2cS> n2a or n2cP <n2cS <n2a, A1 * (n2cS−n2a) / cosθS and B1 * (n2cP−n2a) * cos2θP / cosθP
When n2cP>n2a> n2cS or n2cP <n2a <n2cS, A2 * (n2cS−n2a) / cosθS and −B2 * (n2cP−n2a) * cos2θP / cosθP should be within 10%. a is the values are set, thereby matching as the difference between the period in the thickness dependence of the diffraction efficiency of the S polarized light, and the period in the thickness dependence of the diffraction efficiency of the P polarized light is within 10% Let
Further, the thickness of the diffraction grating is determined based on the above-described thickness dependency characteristic of the diffraction efficiency of S-polarized light and the thickness dependency characteristic of the diffraction efficiency of P-polarized light. The average is set to be 90% or more.
In the above equation, θS is the Bragg angle for S-polarized light, and θP is the Bragg angle for P-polarized light. A1 and A2 are the wave numbers (1 / periods) in the thickness dependence of the diffraction efficiency of the S-polarized light of the diffraction grating obtained by the RCWA method, and the S-polarized light of the transmission-type VPH diffraction grating obtained by the two-wave coupling analysis method. It is a value divided by the wave number (1 / period) in the thickness dependence characteristic of the diffraction efficiency. Further, B1 and B2 are diffractions of P-polarized light of a transmission type VPH diffraction grating obtained by a two-wave coupling analysis method in which the wave number (1 / period) in the thickness dependence characteristic of the diffraction efficiency of P-polarized light of the diffraction grating obtained by the RCWA method is obtained. It is a value divided by the wave number (1 / period) in the thickness dependence characteristic of efficiency. The transmission type VPH diffraction grating described above has a maximum refractive index for S-polarized light of n2cS and n2a, a minimum refractive index of n2cS and n2a, and a maximum refractive index for P-polarized light of n2cP and n2a. Is a transmission type VPH diffraction grating having a larger one of n2cP and a smaller refractive index of n2a.
Further, it can be 95% or more, or 99% or more.
The diffraction grating of the present invention is a diffraction grating different from that of claim 4 , wherein the maximum refractive index for the S-polarized light of the optically anisotropic medium is n2cS and the maximum refractive index for the P-polarized light is n2cP. The refractive index of the other material is n2a, and n2a, n2cS, and n2cP are
In the case of n2cP>n2cS> n2a or n2cP <n2cS <n2a, 2A1 * (n2cS−n2a) / cosθS = B1 * (n2cP−n2a) * cos2θP / cosθP or A1 * (n2cS−n2a) / cosθS = 2B1 * (n2cP-n2a) * cos2θP / cosθP
In the case of n2cP>n2a> n2cS or n2cP <n2a <n2cS, 2A2 * (n2cS−n2a) / cos θS = −B2 * (n2cP−n2a) * cos 2θP / cos θP or A2 * (n2cS−n2a) / cos θS = −2B2 * (n2cP−n2a) * cos2θP / cosθP is set to a value satisfying one of the diffraction efficiencies of S-polarized light and P-polarized light, and one is set to 90% or more and the other is set to 1% or less. . One diffraction efficiency can be 95% or more, or 99% or more.
Note that θS, θP, A1, A2, B1, and B2 in the above formula are the same as described above.
The diffraction grating according to claim 4 is a transmissive diffraction grating having a grating structure in which two types of materials having different refractive indexes are alternately and periodically arranged. If the refractive index of the optically anisotropic medium for S-polarized light is n2cS, the refractive index for P-polarized light is n2cP, and the Bragg angles for S-polarized light and P-polarized light are θS and θP, respectively, n2a, n2cS, and By choosing n2cP

Figure 0006168642
Figure 0006168642

(n2cP>n2cS>n2aまたはn2cP<n2cS<n2aの場合)、     (When n2cP> n2cS> n2a or n2cP <n2cS <n2a),

Figure 0006168642
Figure 0006168642

(n2cP>n2a>n2cSまたはn2cP<n2a<n2cSの場合)
のいずれかを満足するような任意のθSとθPにおいて、式(3)と式(4)が等しくなるために、図7のようにS偏光およびP偏光の1次回折光の回折効率特性が一致する。そして、その一致した極大値において90%以上の回折効率となる。つまり、所望のブラッグ角(言い換えれば所望の格子周期Λ、波長λ)において、式(8)、(9)を満たすよう光学異方性媒質のS偏光に対する屈折率と他の材料の屈折率との差、および光学異方性媒質のP偏光に対する屈折率と他の材料の屈折率との差、の2つを制御すれば、S偏光の回折効率の特性とP偏光の回折効率の特性を一致させて、その一致した極大値となる格子の厚さにおいてS偏光とP偏光の回折効率の平均を90%以上とすることができる。ここでA1とA2は上記RCWA法によって求めた厚い透過型矩形回折格子のS偏光の回折効率の格子の厚さtに関する依存特性における波数(1/周期)PRSを上記2波結合解析法によって求めた厚い透過型VPH回折格子のS偏光の回折効率の格子の厚さtに関する依存特性における波数(1/周期)P2Sで割った値である。また、B1とB2は上記RCWA法によって求めた厚い透過型矩形回折格子のP偏光の回折効率の格子の厚さtに関する依存特性における波数(1/周期)PRPを上記2波結合解析法によって求めた透過型VPH回折格子1のP偏光の回折効率の格子の厚さtに関する依存特性における波数(1/周期)P2Pで割った値である。なお、式(8)および式(9)の左辺と右辺が近似等号によって結ばれているのは、左辺と右辺が厳密に等しくなくても、多くの場合に実用上問題なく利用できるからである。
(When n2cP>n2a> n2cS or n2cP <n2a <n2cS)
In any θS and θP that satisfy any of the above, since the equations (3) and (4) are equal, the diffraction efficiency characteristics of the first-order diffracted light of S-polarized light and P-polarized light are coincident as shown in FIG. To do. The diffraction efficiency is 90% or more at the matched maximum value. That is, at the desired Bragg angle (in other words, the desired grating period Λ, wavelength λ), the refractive index of the optically anisotropic medium with respect to the S-polarized light and the refractive index of other materials so as to satisfy the expressions (8) and (9) And the difference between the refractive index of the optically anisotropic medium for the P-polarized light and the refractive index of the other material, the characteristics of the diffraction efficiency of the S-polarized light and the characteristics of the diffraction efficiency of the P-polarized light can be controlled. By matching, the average of the diffraction efficiencies of S-polarized light and P-polarized light can be 90% or more at the thickness of the grating having the matched maximum value. Here, A1 and A2 are the wave number (1 / period) PRS in the dependence characteristic of the diffraction efficiency of S-polarized light of the thick transmission rectangular diffraction grating obtained by the RCWA method with respect to the thickness t of the grating, and the PRS is obtained by the two-wave coupling analysis method. The wave number (1 / period) in the dependence of the diffraction efficiency of S-polarized light on the thickness t of the thick transmission type VPH diffraction grating, divided by P2S. B1 and B2 are the wave number (1 / period) PRP in the dependence characteristic of the grating thickness t of the P-polarized diffraction efficiency of the thick transmission rectangular diffraction grating obtained by the RCWA method, and the two-wave coupling analysis method. Further, the wave number (1 / period) in the dependence characteristic of the diffraction efficiency of P-polarized light of the transmission type VPH diffraction grating 1 regarding the thickness t of the grating is a value divided by P2P. Note that the reason why the left and right sides of Equations (8) and (9) are connected by an approximate equal sign is that they can be used without practical problems in many cases even if the left and right sides are not exactly equal. is there.

一方、式(6)や式(7)と同様にn2aとn2cSとn2cPを選ぶことによって、つまり式(8)、(9)の右辺または左辺の一方を2倍とした等式を満たすようn2aとn2cSとn2cPを選ぶことによって、任意のθSとθPにおいて、式(3)の格子の厚さtに対する周期が式(4)の格子の厚さtに対する周期の2倍あるいは1/2になり、図4に示す上記ディクソンの条件1のように、S偏光あるいはP偏光の1次回折光の効率が最初の極大になる格子の厚さtにおいて、P偏光あるいはS偏光の1次回折光の効率が0%になる偏光特性を実現できる。つまり、n2cP>n2cS>n2aまたはn2cP<n2cS<n2aの場合に、

Figure 0006168642

または、
Figure 0006168642
あるいは、n2cP>n2cS>n2aまたはn2cP<n2cS<n2aの場合に、
Figure 0006168642

または、
Figure 0006168642

のように、所望のブラッグ角において、式(8)、(9)の右辺または左辺の一方を2倍とした等式を満たすよう一方の材料である光学異方性媒質のS偏光に対する屈折率と他の材料の屈折率との差、および光学異方性媒質のP偏光に対する屈折率と他の材料の屈折率との差、および格子の厚さtの3つを制御すれば、S偏光とP偏光のうち、一方を90%以上の回折効率とし、他方を1%以下の回折効率とすることができ、偏光分離素子として機能させることができる。なお、式(10)〜(13)の左辺と右辺が近似等号によって結ばれているのは、左辺と右辺が厳密に等しくなくても、多くの場合に実用上問題なく利用できるからである。
以上のことから、所望のブラッグ角において、一方の材料である光学異方性媒質のS偏光に対する屈折率と他の材料の屈折率との差、および光学異方性媒質のP偏光に対する屈折率と他の材料の屈折率との差、および格子の厚さtを制御すれば、S偏光の回折効率と、P偏光の回折効率を所望の特性とすることができることがわかる。 On the other hand, n2a is satisfied by selecting n2a, n2cS, and n2cP in the same manner as in Expression (6) and Expression (7), that is, satisfying the equality in which one of the right side or the left side of Expressions (8) and (9) is doubled. And n2cS and n2cP, the period with respect to the grating thickness t in equation (3) becomes twice or ½ the period with respect to the grating thickness t in equation (4) at any θS and θP. 4, the efficiency of the first-order diffracted light of P-polarized light or S-polarized light at the thickness t of the grating where the efficiency of the first-order diffracted light of S-polarized light or P-polarized light reaches the first maximum, as in the Dixon condition 1 shown in FIG. A polarization characteristic of 0% can be realized. That is, when n2cP>n2cS> n2a or n2cP <n2cS <n2a,
Figure 0006168642

Or
Figure 0006168642
Alternatively, if n2cP>n2cS> n2a or n2cP <n2cS <n2a,
Figure 0006168642

Or
Figure 0006168642

As shown, the refractive index with respect to the S-polarized light of the optically anisotropic medium, which is one of the materials, satisfies the equation where one of the right side or the left side of the formulas (8) and (9) is doubled at the desired Bragg angle. S-polarized light can be controlled by controlling the difference between the refractive index of the other material and the refractive index of the optically anisotropic medium, the difference between the refractive index of the optically anisotropic medium and the refractive index of the other material, and the thickness t of the grating. And P-polarized light, one can have a diffraction efficiency of 90% or more and the other can have a diffraction efficiency of 1% or less, and can function as a polarization separation element. The reason why the left side and the right side of the equations (10) to (13) are connected by an approximate equal sign is that even if the left side and the right side are not exactly equal, they can be used without any practical problems in many cases. .
From the above, at the desired Bragg angle, the difference between the refractive index of the optically anisotropic medium, which is one material, with respect to S-polarized light and the refractive index of the other material, and the refractive index of the optically anisotropic medium with respect to P-polarized light. It can be seen that the diffraction efficiency of S-polarized light and the efficiency of diffraction of P-polarized light can be made to have desired characteristics by controlling the difference between the refractive index of the other material and the refractive index of other materials and the thickness t of the grating.

本発明の回折格子の光学異方性媒質として、液晶、光配向性樹脂、延伸された樹脂、一軸性結晶や二軸性結晶、ホトニッククリスタル、メタマテリアル等が利用できる。
本発明の回折格子を格子周期方向に伸びる直線状または曲線状とし、それをコア材およびクラッド材により埋め込むことで、平面型の光導波路としてもよい。光導波路においては、本明細書中のS偏光をTE波、P偏光をTM波と置き替えて読めばよい。
As the optically anisotropic medium of the diffraction grating of the present invention, liquid crystal, photo-alignment resin, stretched resin, uniaxial crystal, biaxial crystal, photonic crystal, metamaterial, and the like can be used.
The diffraction grating of the present invention may be a linear or curved shape extending in the grating period direction and embedded with a core material and a clad material to form a planar optical waveguide. In the optical waveguide, the S-polarized light in this specification may be read by replacing it with the TE wave and the P-polarized light with the TM wave.

請求項1、4に記載の回折格子は、任意のブラッグ角θにおいて、S偏光に対する回折効率とP偏光に対する回折効率とを所望の特性とすることができる。
特に、請求項1に記載の回折格子においては式(5)を満たすように光学異方性媒質の屈折率を調整し、請求項4に記載の回折格子においては式(8)あるいは式(9)を満たすように光学異方性媒質の屈折率を調整し、格子の厚さtを調整することによって、S偏光とP偏光が同時に90%以上、最大100%に達する高い回折効率と広い帯域幅を達成することができるという利点がある。
The diffraction gratings according to claims 1 and 4 can achieve desired characteristics of diffraction efficiency for S-polarized light and diffraction efficiency for P-polarized light at an arbitrary Bragg angle θ.
In particular, in the diffraction grating according to claim 1, the refractive index of the optical anisotropic medium is adjusted so as to satisfy the expression (5), and in the diffraction grating according to claim 4, the expression (8) or the expression (9) ) To adjust the refractive index of the optically anisotropic medium and the thickness t of the grating so that the S-polarized light and the P-polarized light are simultaneously 90% or more, and a high diffraction efficiency and a wide band reaching a maximum of 100%. There is an advantage that the width can be achieved.

また、請求項1とは別の回折格子は、任意のブラッグ角θにおいて、式(6)あるいは式(7)を満足するように光学異方性媒質の屈折率を調整することによって、一方の偏光の回折効率が1%以下(最小0%)、他方の偏光の回折効率が90%以上(最大100%)に達するような偏光分離機能が付加された回折格子を高い回折効率で実現できるという利点がある。同様に請求項4とは別の回折格子は、任意のブラッグ角θにおいて、一方の材料である光学異方性媒質の屈折率と他方の材料の屈折率を調整し、格子の厚さtを調整することによって、一方の偏光の回折効率が1%以下(最小0%)、他方の偏光の回折効率が90%以上(最大100%)に達するような偏光分離機能が付加された回折格子を高い回折効率を実現できるという利点がある。 Further, a diffraction grating different from that of the first aspect can be obtained by adjusting the refractive index of the optically anisotropic medium so as to satisfy the formula (6) or the formula (7) at an arbitrary Bragg angle θ. It is possible to realize a diffraction grating with a polarization separation function with a high diffraction efficiency so that the polarization diffraction efficiency reaches 1% or less ( minimum 0%) and the polarization efficiency of the other polarization reaches 90% or more (maximum 100%). There are advantages. Similarly, a diffraction grating different from claim 4 adjusts the refractive index of the optically anisotropic medium, which is one material, and the refractive index of the other material at an arbitrary Bragg angle θ, and sets the thickness t of the grating. By adjusting the diffraction grating, the polarization separation function is added so that the diffraction efficiency of one polarization reaches 1% or less ( minimum 0%) and the diffraction efficiency of the other polarization reaches 90% or more (maximum 100%). There is an advantage that high diffraction efficiency can be realized.

請求項4に記載の回折格子は、高次回折光においても適用可能である。   The diffraction grating according to claim 4 can also be applied to higher-order diffracted light.

従来の厚い透過型VPH回折格子1や厚い透過型矩形回折格子2は、回折格子内部においてブラッグの条件を満足する次数の回折光と入射光が直交する場合にその回折次数の格子と直交する偏光の電界ベクトル成分が0になってしまうために、P偏光の回折効率が著しく低下してしまう。請求項1に記載の回折格子は、P偏光の入射光と回折光が直交しないように光学異方性材料のP偏光の平均屈折率や液晶等の配向方向を調整することによって、上記回折次数のP偏光の回折効率の低下を防止あるいは軽減することが可能である。また、請求項4に記載の回折格子は、P偏光において入射光と回折光が直交しないように液晶等の配向方向や、2つの材料のP偏光の屈折率の組み合わせを選ぶことによって上記回折次数のP偏光の回折効率の低下を防止あるいは軽減することが可能である。 The conventional thick transmission type VPH diffraction grating 1 and thick transmission type rectangular diffraction grating 2 are polarized light orthogonal to the diffraction order grating when the diffraction light of the order satisfying the Bragg condition and the incident light are orthogonal within the diffraction grating. Therefore, the diffraction efficiency of P-polarized light is significantly reduced. The diffraction grating according to claim 1 is characterized in that the diffraction order is adjusted by adjusting an average refractive index of P-polarized light of an optically anisotropic material and an alignment direction of liquid crystal so that incident light of P-polarized light and diffracted light are not orthogonal to each other. It is possible to prevent or reduce the decrease in diffraction efficiency of P-polarized light. In the diffraction grating according to claim 4 , the diffraction order is selected by selecting the orientation direction of the liquid crystal or the like and the combination of the refractive indices of the P-polarized light of the two materials so that the incident light and the diffracted light are not orthogonal in the P-polarized light. It is possible to prevent or reduce the decrease in diffraction efficiency of P-polarized light.

請求項1に記載の回折格子や請求項4に記載の回折格子は、光学異方性媒質として硬化型液晶材料を使用し、電界等によって液晶の配向方位を制御することによって製造過程において偏光回折効率特性の調整が容易になる。   The diffraction grating according to claim 1 or the diffraction grating according to claim 4 uses a curable liquid crystal material as an optically anisotropic medium, and polarization diffraction in a manufacturing process by controlling an orientation direction of liquid crystal by an electric field or the like. Adjustment of efficiency characteristics is facilitated.

請求項1に記載の回折格子や請求項4に記載の回折格子は、光学異方性媒質として液晶材料を使用して、電極あるいは透明電極を配置することによって、S偏光およびP偏光に対する回折効率を変動させることが可能な能動的な回折光学素子を実現できる。
なお、本発明の回折格子を用いた請求項10に記載の光導波路についても、上記と同様の利点を得ることができる。
The diffraction grating according to claim 1 and the diffraction grating according to claim 4 use a liquid crystal material as an optically anisotropic medium and dispose an electrode or a transparent electrode, thereby enabling diffraction efficiency for S-polarized light and P-polarized light. It is possible to realize an active diffractive optical element capable of varying the above.
The same advantages as described above can also be obtained for the optical waveguide according to claim 10 using the diffraction grating of the present invention.

図1は、ホログラフィック回折格子露光用の二光束干渉計の二光束の偏光方位と振幅および干渉縞の偏光方位と振幅およびVPH回折格子の概念図である。FIG. 1 is a conceptual diagram of the polarization direction and amplitude of two beams and the polarization direction and amplitude of interference fringes and a VPH diffraction grating of a two-beam interferometer for holographic diffraction grating exposure. 図2は、VPH回折格子の回折効率の分光特性の実測値を示した図である。FIG. 2 is a diagram showing measured values of the spectral characteristics of the diffraction efficiency of the VPH diffraction grating. 図3は、図2のVPH回折格子の厚さに対する回折効率の数値計算の結果を示した図である。FIG. 3 is a diagram showing the results of numerical calculation of diffraction efficiency with respect to the thickness of the VPH diffraction grating of FIG. 図4は、VPH回折格子のP偏光の最初の極大の厚さにおいてS偏光の効率が極小となるような条件(ディクソンの条件1)における厚さに対する回折効率の計算値を示した図である。FIG. 4 is a diagram showing a calculated value of the diffraction efficiency with respect to the thickness under the condition (Dickson's condition 1) in which the efficiency of the S-polarized light becomes minimum at the first maximum thickness of the P-polarized light of the VPH diffraction grating. . 図5はVPH回折格子のP偏光の最初の極大の厚さにおいてS偏光の効率が第二極大となるように調整して、いずれの偏光の回折効率も最大100%に達するような条件(ディクソンの条件2)における厚さに対する回折効率の計算値を示した図である。FIG. 5 shows a condition (Dixon) in which the diffraction efficiency of any polarization reaches a maximum of 100% by adjusting the efficiency of the S polarization at the first maximum thickness of the P polarization of the VPH diffraction grating. It is the figure which showed the calculated value of the diffraction efficiency with respect to the thickness in condition 2). 図6は、厚い透過型矩形回折格子の概念図である。FIG. 6 is a conceptual diagram of a thick transmissive rectangular diffraction grating. 図7は、回折格子3によってS偏光とP偏光の特性を一致させた場合の厚さに対する回折効率の計算値を示した図である。FIG. 7 is a diagram showing a calculated value of the diffraction efficiency with respect to the thickness when the characteristics of the S-polarized light and the P-polarized light are matched by the diffraction grating 3. 図8は、実施例1の回折格子3の構成を示した図である。FIG. 8 is a diagram illustrating a configuration of the diffraction grating 3 according to the first embodiment. 図9は、実施例2の光導波路4の構成を示した図である。FIG. 9 is a diagram illustrating the configuration of the optical waveguide 4 according to the second embodiment. 図10は、実施例3の回折格子5の構成を示した図である。FIG. 10 is a diagram illustrating a configuration of the diffraction grating 5 according to the third embodiment. 図11は、実施例5の光導波路6の構成を示した図である。FIG. 11 is a diagram illustrating the configuration of the optical waveguide 6 according to the fifth embodiment. 図12は、実施例6の回折格子7の構成を示した図である。FIG. 12 is a diagram illustrating the configuration of the diffraction grating 7 according to the sixth embodiment. 図13は、二軸性異方性の液晶の座標面内を伝搬する光束について電界が座標面と平行に振動する偏光(実線)および垂直に振動する偏光(破線)の入射方位の屈折率を示した図である。FIG. 13 shows the refractive indexes of incident azimuths of polarized light (solid line) whose electric field oscillates parallel to the coordinate surface (polarized line) and polarized light (broken line) oscillates perpendicularly to the light beam propagating in the coordinate plane of the biaxially anisotropic liquid crystal. FIG. 図14は、実施例7の光導波路8の概念図である。FIG. 14 is a conceptual diagram of the optical waveguide 8 of the seventh embodiment. 図15は、実施例8の回折格子9の概念図である。FIG. 15 is a conceptual diagram of the diffraction grating 9 according to the eighth embodiment. 図16は、実施例9の光導波路10の概念図である。FIG. 16 is a conceptual diagram of the optical waveguide 10 of the ninth embodiment.

図8の正面図(側面図でのA−A断面図)および側面図(入射面での断面図)に示すような回折格子3の製作方法を説明する。従来VPH回折格子の作製に用いられていたホログラム樹脂に替えて、次のような材料を用いる。その材料は、直線偏光の照射によって近接する2分子の光官能基が偏光の電界振動方向と平行である場合に選択的に二量化するような光学異方性の液晶性有機材料210と、屈折率が等方性の熱硬化型樹脂材料220と、を主成分とする光学異方性のホログラム樹脂230である。二枚のガラス、樹脂、結晶等である基板200と基板240の間に、ガラスビーズ等のスペーサ(図示しない)が混入された上記ホログラム樹脂230を挟んでホログラム乾板を作製する。あるいは、このホログラム樹脂230をガラス、樹脂、結晶等の基板200に塗布してもよい。
次に、図8の上部に示した矢印のように、回折格子の周期方向とする方向に偏光させた二光束のレーザ干渉露光によって、干渉縞の明部では、偏光の電界振動方向に長軸が配置されている液晶性有機材料210の感光性基が選択的に架橋反応を起こして二量化する。二量化した液晶性有機材料210の周囲では、単量体の液晶性有機材料210が二量化した液晶性有機材料210と同じ方向に配列して、レーザ干渉露光中には近接する単量体の液晶性有機材料210と二量化する。その結果、干渉縞の明部においては単量体の液晶性有機材料210の濃度が低下するために、干渉縞の暗部から単量体の液晶性有機材料210が明部に移動し、一方、明部から熱硬化型樹脂220が暗部に移動し、明部に移動した単量体の液晶性有機材料210は二量化した液晶性有機材料210と同じ方向に配向して近接する単量体の液晶性有機材料と二量化する。
レーザ干渉露光の後に、上記ホログラム乾板を熱硬化性樹脂220の硬化温度まで加熱して常温まで冷却することによって、図8の正面図あるいは側面図のような回折格子の周期方向に液晶性有機材料210が配向した、本発明の回折格子3を実現できる。
回折格子3は、液晶性有機材料210の濃度の違いによって、ホログラム樹脂230の屈折率が正弦波状に変化するVPHである。また、液晶性有機材料210の配向により、その液晶性有機材料210のS偏光に対する屈折率とP偏光に対する屈折率とは異なっている。
なお、実施例1の回折格子3は、図8の側面図に示すように、ホログラム樹脂230の厚さ方向(光の入射面に対して垂直な方向)については液晶性有機材料210の濃度を均一として屈折率の変化が内容にしているが、図9の上面図のように、厚さ方向の液晶性有機材料210の濃度を変化させることで、厚さ方向の屈折率が角度αの傾斜を有するようにしてもよい。
そして、実施例1の回折格子3は、ホログラム樹脂230のS偏光に対する最大屈折率nSmaxと最小屈折率nSminとの差:nSmax−nSmin、およびP偏光に対する最大屈折率nPmaxと最小屈折率nPminとの差:nPmax−nPminを、式(5)を満たす所定の値に制御することにより、S偏光およびP偏光の1次回折光の回折効率特性(回折効率の格子厚さt依存性)を一致させることができ、格子の厚さtを調整することによって回折格子3への所望の入射角に対して、S偏光とP偏光の回折効率の平均値を90%以上とすることができる。もちろん、上記差の二分の一、つまり、S偏光に対する屈折率変調量:ΔnS=(nSmax−nSmin)/2、および、P偏光に対する屈折率変調量:ΔnP=(nPmax−nPmin)/2によって制御してもよい。
また、ホログラム樹脂230のS偏光に対する最大屈折率nSmaxと最小屈折率nSminとの差、およびP偏光に対する最大屈折率nPmaxと最小屈折率nPminとの差を、式(6)または式(7)を満たす所定の値に制御することにより、S偏光の1次回折光の回折効率特性が極大となるときにP偏光の1次回折光の回折効率特性が極小となるように、あるいはその逆に、S偏光の1次回折光の回折効率特性が極小となるときにP偏光の1次回折光の回折効率特性が極大となるようにことができる。そのため、回折格子3への所望の入射角に対して、S偏光の回折効率が90%以上でP偏光の回折効率が1%以下、またはS偏光の回折効率が1%以下でP偏光の回折効率が90%以上とすることができ、回折格子3を偏光分離素子とすることができる。
A manufacturing method of the diffraction grating 3 as shown in the front view (AA cross-sectional view in the side view) and the side view (cross-sectional view in the incident surface) of FIG. 8 will be described. The following materials are used in place of the hologram resin that has been conventionally used for manufacturing the VPH diffraction grating. The material is composed of an optically anisotropic liquid crystalline organic material 210 that selectively dimerizes when two adjacent photofunctional groups are parallel to the direction of electric field vibration of polarized light by irradiation with linearly polarized light, and refraction. An optically anisotropic hologram resin 230 mainly composed of a thermosetting resin material 220 having an isotropic rate. A hologram dry plate is produced by sandwiching the hologram resin 230 in which a spacer (not shown) such as glass beads is mixed between a substrate 200 and a substrate 240, which are two pieces of glass, resin, crystal, or the like. Alternatively, the hologram resin 230 may be applied to a substrate 200 such as glass, resin, or crystal.
Next, as indicated by the arrows shown in the upper part of FIG. 8, the long axis in the direction of the electric field oscillation of the polarized light in the bright part of the interference fringes is obtained by laser interference exposure of two light beams polarized in the direction of the diffraction grating period. The photosensitive group of the liquid crystal organic material 210 in which is placed selectively undergoes a crosslinking reaction to dimerize. Around the dimerized liquid crystal organic material 210, the monomer liquid crystal organic material 210 is aligned in the same direction as the dimerized liquid crystal organic material 210, and during the laser interference exposure, the adjacent monomer liquid crystal organic material 210 is aligned. Dimerizes with the liquid crystalline organic material 210. As a result, since the concentration of the monomer liquid crystalline organic material 210 decreases in the bright part of the interference fringes, the monomer liquid crystalline organic material 210 moves from the dark part of the interference fringes to the bright part, The thermosetting resin 220 moves from the bright part to the dark part, and the liquid crystalline organic material 210 of the monomer that has moved to the bright part is aligned in the same direction as the dimerized liquid crystalline organic material 210 and is close to the monomer. Dimerize with liquid crystalline organic materials.
After the laser interference exposure, the hologram dry plate is heated to the curing temperature of the thermosetting resin 220 and cooled to room temperature, whereby a liquid crystalline organic material is formed in the periodic direction of the diffraction grating as shown in the front view or side view of FIG. The diffraction grating 3 of the present invention in which 210 is oriented can be realized.
The diffraction grating 3 is a VPH in which the refractive index of the hologram resin 230 changes in a sine wave shape due to the difference in concentration of the liquid crystalline organic material 210. Further, the refractive index for S-polarized light and the refractive index for P-polarized light of the liquid-crystalline organic material 210 are different depending on the orientation of the liquid-crystalline organic material 210.
In the diffraction grating 3 of Example 1, as shown in the side view of FIG. 8, the concentration of the liquid crystalline organic material 210 is set in the thickness direction of the hologram resin 230 (direction perpendicular to the light incident surface). The content of the change in the refractive index is uniform, but the refractive index in the thickness direction is inclined at an angle α by changing the concentration of the liquid crystal organic material 210 in the thickness direction as shown in the top view of FIG. You may make it have.
The diffraction grating 3 of Example 1 is different from the maximum refractive index nSmax and the minimum refractive index nSmin for the S-polarized light of the hologram resin 230: nSmax−nSmin, and the maximum refractive index nPmax and the minimum refractive index nPmin for the P-polarized light. Difference: By controlling nPmax-nPmin to a predetermined value satisfying the equation (5), the diffraction efficiency characteristics of the first-order diffracted light of S-polarized light and P-polarized light (dependence of diffraction efficiency on the grating thickness t) are matched. By adjusting the thickness t of the grating, the average value of the diffraction efficiencies of S-polarized light and P-polarized light can be 90% or more with respect to a desired incident angle to the diffraction grating 3. Of course, it is controlled by a half of the difference, that is, the refractive index modulation amount for S-polarized light: ΔnS = (nSmax−nSmin) / 2 and the refractive index modulation amount for P-polarized light: ΔnP = (nPmax−nPmin) / 2. May be.
Further, the difference between the maximum refractive index nSmax and the minimum refractive index nSmin with respect to the S-polarized light of the hologram resin 230 and the difference between the maximum refractive index nPmax and the minimum refractive index nPmin with respect to the P-polarized light are expressed by Equation (6) or Equation (7). By controlling to a predetermined value to satisfy, the diffraction efficiency characteristic of the first-order diffracted light of P-polarized light becomes the minimum when the diffraction efficiency characteristic of the first-order diffracted light of S-polarization becomes maximum, or vice versa. When the diffraction efficiency characteristic of the first-order diffracted light is minimized, the diffraction efficiency characteristic of the P-polarized first-order diffracted light can be maximized. Therefore, with respect to the desired incident angle to the diffraction grating 3, the diffraction efficiency of S-polarized light is 90% or more and the diffraction efficiency of P-polarized light is 1% or less, or the diffraction efficiency of S-polarized light is 1% or less and The efficiency can be 90% or more, and the diffraction grating 3 can be a polarization separation element.

上記偏光配向性の液晶性有機材料210が一軸性の液晶であり、常光線屈折率がno=1.5、異常光線屈折率がne=1.7、熱硬化性樹脂220の屈折率が1.59である場合に、回折格子3はnSmax=1.59、nSmin=1.5、nPmax=1.7、nPmin=1.59であるとすると、式(5)およびスネルの式(2)より、S偏光に対するブラッグ角がθS=18.6°、P偏光に対するブラッグ角がθP=17.4°(真空中のブラッグ角:θ0=29.4°)のときにS偏光とP偏光の特性が一致する。図7は波長:λ=0.6μmにおいて実施例1の回折格子3によってS偏光とP偏光の特性を一致させた場合の厚さに対する回折効率の計算値を示した図である。なお、図7は、S偏光の回折効率の特性とP偏光の回折効率の特性とを見易くするために、式(5)が等式になる条件よりブラッグ角が若干小さくなるように格子周期をΛ=0.646μmとしてあり、S偏光に対するブラッグ角がθS=17.5°、P偏光に対するブラッグ角がθP=16.4°(真空中のブラッグ角はいずれもθ0=27.7°)であり、ホログラム樹脂230の厚さt=3.1においてS偏光とP偏光の回折効率の平均値が99.9%である。   The polarizing alignment liquid crystalline organic material 210 is a uniaxial liquid crystal, the ordinary ray refractive index is no = 1.5, the extraordinary ray refractive index is ne = 1.7, and the refractive index of the thermosetting resin 220 is 1. .5, the diffraction grating 3 has nSmax = 1.59, nSmin = 1.5, nPmax = 1.7, and nPmin = 1.59. Equation (5) and Snell's equation (2) Therefore, when the Bragg angle for S-polarized light is θS = 18.6 ° and the Bragg angle for P-polarized light is θP = 17.4 ° (Bragg angle in vacuum: θ0 = 29.4 °), S-polarized light and P-polarized light The characteristics match. FIG. 7 is a diagram showing a calculated value of diffraction efficiency with respect to thickness when the characteristics of S-polarized light and P-polarized light are matched by the diffraction grating 3 of Example 1 at a wavelength: λ = 0.6 μm. In FIG. 7, in order to make it easier to see the characteristics of S-polarized light and P-polarized light, the grating period is set so that the Bragg angle is slightly smaller than the condition in which Equation (5) becomes an equation. Λ = 0.646 μm, the Bragg angle for S-polarized light is θS = 17.5 °, the Bragg angle for P-polarized light is θP = 16.4 ° (the Bragg angles in vacuum are both θ0 = 27.7 °). The average value of the diffraction efficiency of S-polarized light and P-polarized light is 99.9% at the thickness t = 3.1 of the hologram resin 230.

図9に示す実施例2の光導波路4の製作方法として、実施例1のような方法で製作された回折格子3のホログラム樹脂230を格子と垂直あるいは任意の方位に切断して格子周期方向に伸びる直線状あるいは曲線状の形状に加工し、これをコア層310とクラッド層300に埋設することによって、平面光導波路である光導波路4を実現できる。
この光導波路4は、回折格子3のホログラム樹脂230の屈折率を実施例1で示したように制御することにより、TE波およびTM波の回折効率の特性を所望の特性に制御することが可能である。
As a manufacturing method of the optical waveguide 4 of the second embodiment shown in FIG. 9, the hologram resin 230 of the diffraction grating 3 manufactured by the method as in the first embodiment is cut in a direction perpendicular to the grating or in an arbitrary direction in the grating periodic direction. An optical waveguide 4 that is a planar optical waveguide can be realized by processing into an extending linear or curved shape and embedding it in the core layer 310 and the cladding layer 300.
This optical waveguide 4 can control the diffraction efficiency characteristics of TE wave and TM wave to desired characteristics by controlling the refractive index of the hologram resin 230 of the diffraction grating 3 as shown in the first embodiment. It is.

図10に示す実施例3の回折格子5の製作方法として、任意の方位に切り出した光学異方性の結晶あるいは延伸によって光学異方性が生じた樹脂等の光学異方性媒質の基板400にフォトリソグラフィとエッチング技術等によってストライプ状の溝410を形成して深い矩形格子420を形成し、任意の屈折率を有する樹脂等の光学等方性媒質450を充填し、その上に基板430を配置して封止することによって回折格子5を実現することができる。図10のように、光学異方性媒質である基板400の光学軸は、溝410のストライプ方向と同一の方向である。
逆に、光学等方性の基板に断面が矩形のストライプ状の溝を形成し、溝に光学異方性媒質を充填することで回折格子5を形成してもよい。この場合、光学異方性媒質には、電界や配光の照射などによって所定の方向に配向させた状態で硬化させた液晶を用いることができる。
また、光学等方性の基板に光学異方性の膜を形成し、膜をエッチングして断面が矩形のストライプ状の溝を形成し、溝に光学等方性媒質を充填することで回折格子5を形成してもよい。光学異方性の膜には、延伸された樹脂、または配向された状態で硬化した液晶などを用いることができる。
As a method for manufacturing the diffraction grating 5 of Example 3 shown in FIG. 10, an optically anisotropic crystal cut out in an arbitrary orientation or an optically anisotropic medium substrate 400 such as a resin having optical anisotropy caused by stretching is used. Striped grooves 410 are formed by photolithography and etching techniques to form a deep rectangular lattice 420, filled with an optical isotropic medium 450 such as a resin having an arbitrary refractive index, and a substrate 430 is disposed thereon. Then, the diffraction grating 5 can be realized by sealing. As shown in FIG. 10, the optical axis of the substrate 400, which is an optically anisotropic medium, is the same direction as the stripe direction of the groove 410.
Conversely, the diffraction grating 5 may be formed by forming a striped groove having a rectangular cross section on an optically isotropic substrate and filling the groove with an optically anisotropic medium. In this case, the optically anisotropic medium can be a liquid crystal that is cured while being aligned in a predetermined direction by irradiation of an electric field or light distribution.
Further, a diffraction grating is formed by forming an optically anisotropic film on an optically isotropic substrate, etching the film to form a striped groove having a rectangular cross section, and filling the groove with an optically isotropic medium. 5 may be formed. For the optically anisotropic film, a stretched resin, a liquid crystal cured in an aligned state, or the like can be used.

例えば光学異方性の結晶材料として、フッ化イットリウム−リチウム(YLiF4:YLF)やβ−メタホウ酸バリウム(β−BaB2O4:β−BBO)、ニオブ酸リチウム(LiNbO3)等が挙げられる。また、可視光における樹脂の平均屈折率は1.35〜1.74程度である。このうちβ−BBOは常光線と異常光線の屈折率差が大きく、常光線屈折率:no=1.669および異常光線屈折率:ne=1.551であり、屈折率:n2a=1.35〜1.5あるいはn2a=1.6近傍あるいはn2a=1.7〜1.74の樹脂等と組み合わせることにより、広い回折効率の波長帯域幅を実現できる。なお、非特許文献8によれば、格子以外の部分の基板が光学異方性を有していても平行平面板とみなせる場合には、後置される光学等方性媒質450中に出射後のS偏光とP偏光の回折角は平行平面板部分の光学異方性(複屈折)の影響を受けずに等しいために、溝410が基板400まで貫通しなくても構わない。
この回折格子5は、光学等方性媒質450の屈折率n2aおよび、光学異方性媒質である基板400のS偏光に対する屈折率n2cSとP偏光に対する屈折率n2cPとを、式(8)または式(9)を満たす所定の値に制御することにより、図7のようにS偏光およびP偏光の1次回折光の回折効率特性を一致させることができ、回折格子5への所望の入射角に対して、S偏光とP偏光の回折効率の平均値を90%以上とすることができる。
また、光学等方性媒質450の屈折率n2aおよび光学異等方性媒質である基板400のS偏光に対する屈折率n2cS、P偏光に対する屈折率n2cPを、式(8)、(9)の左辺または右辺の一方を2倍とした等式、つまり、式(10)、(11)、(12)、(13)のいずれかを満たす所定値に制御することにより、S偏光の1次回折光の回折効率特性が極大となるときにP偏光の1次回折光の回折効率特性が極小となるように、あるいはその逆に、S偏光の1次回折光の回折効率特性が極小となるときにP偏光の1次回折光の回折効率特性が極大となるようにことができる。そのため、回折格子5への所望の入射角に対して、S偏光の回折効率が90%以上でP偏光の回折効率が1%以下、またはS偏光の回折効率が1%以下でP偏光の回折効率が90%以上とすることができ、回折格子5を偏光分離素子とすることができる。
なお、実施例3の回折格子5では、溝410を光の入射面に対して垂直なものとしたが、図11の上面図に示すように、溝410を光の入射面に垂直な方向に対して角度α傾斜させ、光学異方性媒質と光学等方性媒質が交互に傾斜して配列された構造としてもよい。
Examples of optically anisotropic crystal materials include yttrium fluoride-lithium (YLiF4: YLF), β-barium metaborate (β-BaB2O4: β-BBO), and lithium niobate (LiNbO3). The average refractive index of the resin in visible light is about 1.35 to 1.74. Of these, β-BBO has a large difference in refractive index between ordinary light and extraordinary light, ordinary light refractive index: no = 1.669, extraordinary light refractive index: ne = 1.551, and refractive index: n2a = 1.35. A wavelength band with a wide diffraction efficiency can be realized by combining with a resin having a value of about 1.5 or n2a = 1.6 or n2a = 1.7 to 1.74. According to Non-Patent Document 8, when the substrate other than the grating has optical anisotropy and can be regarded as a plane parallel plate, it is emitted into the optically isotropic medium 450 to be placed later. Since the diffraction angles of S-polarized light and P-polarized light are equal without being affected by the optical anisotropy (birefringence) of the plane-parallel plate portion, the groove 410 may not penetrate to the substrate 400.
The diffraction grating 5 has a refractive index n2a of the optical isotropic medium 450 and a refractive index n2cS for the S-polarized light and a refractive index n2cP for the P-polarized light of the substrate 400, which is an optically anisotropic medium. By controlling to a predetermined value that satisfies (9), the diffraction efficiency characteristics of the first-order diffracted light of S-polarized light and P-polarized light can be matched as shown in FIG. Thus, the average value of the diffraction efficiencies of S-polarized light and P-polarized light can be 90% or more.
Further, the refractive index n2a of the optically isotropic medium 450 and the refractive index n2cS for the S-polarized light and the refractive index n2cP for the P-polarized light of the substrate 400, which is an optically anisotropic medium, are represented by the left side of the equations (8) and (9) or Diffraction of S-polarized first-order diffracted light by controlling to a predetermined value satisfying any one of the equations in which one of the right-hand sides is doubled, that is, equations (10), (11), (12), and (13) When the efficiency characteristic is maximized, the diffraction efficiency characteristic of the P-polarized first-order diffracted light is minimized, or conversely, when the diffraction efficiency characteristic of the S-polarized first-order diffracted light is minimized, 1 of the P-polarized light The diffraction efficiency characteristic of the next diffracted light can be maximized. Therefore, with respect to a desired incident angle to the diffraction grating 5, the diffraction efficiency of S-polarized light is 90% or more and the diffraction efficiency of P-polarized light is 1% or less, or the diffraction efficiency of S-polarized light is 1% or less. The efficiency can be 90% or more, and the diffraction grating 5 can be a polarization separation element.
In the diffraction grating 5 of Example 3, the groove 410 is perpendicular to the light incident surface. However, as shown in the top view of FIG. 11, the groove 410 is oriented in a direction perpendicular to the light incident surface. Alternatively, the structure may be configured such that the optically anisotropic medium and the optically isotropic medium are alternately inclined and arranged at an angle α.

実施例4の回折格子の製作方法として、第1透明基板あるいは第1透明基板に付与された透明媒質の膜をフォトリソグラフィやエッチング技術等によってストライプ状の溝を形成して深い矩形格子を形成し、溝の底部に任意の方位とプレティルト角に液晶を配向される液晶配向膜を配置し、溝に硬化型の液晶を充填し、第2透明基板によって液晶を封止して、紫外線等によって硬化することにより、実施例3の回折格子5とほぼ同一の構成である実施例4の回折格子を実現することができる。なお、第2透明基板の液晶に接する面にも溝の底部と略同じ方位に液晶を配向される液晶配向膜を配置しても良い。   As a method of manufacturing the diffraction grating of Example 4, a deep rectangular grating is formed by forming a stripe-shaped groove on the first transparent substrate or a transparent medium film applied to the first transparent substrate by photolithography or etching technique. The liquid crystal alignment film that aligns the liquid crystal in an arbitrary orientation and pretilt angle is placed at the bottom of the groove, the groove is filled with a curable liquid crystal, the liquid crystal is sealed with a second transparent substrate, and cured by ultraviolet rays or the like By doing so, it is possible to realize the diffraction grating of the fourth embodiment that has substantially the same configuration as the diffraction grating 5 of the third embodiment. Note that a liquid crystal alignment film that aligns the liquid crystal in substantially the same direction as the bottom of the groove may be disposed on the surface of the second transparent substrate that contacts the liquid crystal.

図11に示す実施例5の光導波路6の製作方法として、実施例3あるいは実施例4のような方法で製作された回折格子5を格子と垂直あるいは任意の方位に切断して格子周期方向に伸びる直線状あるいは曲線状の形状に加工し、これをコア層510とクラッド層500に埋設することによって、平面光導波路である光導波路6を実現できる。光導波路6の埋設された回折格子部分は、図11のように、光学異方性媒質530と光学等方性媒質520が傾斜して交互に配列された構造である。   As a method of manufacturing the optical waveguide 6 of Example 5 shown in FIG. 11, the diffraction grating 5 manufactured by the method of Example 3 or Example 4 is cut perpendicularly to the grating or in an arbitrary direction so as to be in the grating period direction. An optical waveguide 6 that is a planar optical waveguide can be realized by processing into an extending linear or curved shape and embedding it in the core layer 510 and the cladding layer 500. As shown in FIG. 11, the diffraction grating portion in which the optical waveguide 6 is embedded has a structure in which the optical anisotropic medium 530 and the optical isotropic medium 520 are alternately arranged in an inclined manner.

図12に示す実施例6の回折格子7の製作方法を以下に説明する。下基板700と上基板730を任意の厚さの隙間を開けて対向する配置とし、下基板700および上基板730の対向する側の面それぞれには、上下同一格子周期かつ、任意のデューティ比をなす透明電極710の格子を配置する。この時、下基板700側に設けた透明電極710と、上基板730側に設けた透明電極710は対向するように配置する。また、下基板700と上基板730の対向する側の面(液晶に接する面)および透明電極710が液晶に接する面に液晶配向膜720を配置する。次に、下基板700と上基板730との間の隙間に液晶740を充填する。液晶740は、強誘電性であるために自発的なキラリティ(Chirality:3次元の図形や物体がその鏡像と重ね合わすことができない性質。掌性。)によって二軸性光学異方性を発現する液晶(バナナ型液晶やディスク型液晶等)であり、任意の方位と下基板700および上基板730に平行あるいは任意のプレティルト角に配向するようにする。また、図12の側面図のように、液晶740の分子750の長軸が上下の電極方向(電気力線に平行な方向)に傾き、キラリティが消失して液晶740の分子750が一軸性光学異性体として振る舞い、透明電極710の間に位置する液晶740の分子750からの距離が離れるに従って、上下の透明電極710の間に位置する液晶740の分子750の傾きから徐々に下基板700および上基板730に平行あるいはプレティルト角に液晶740の傾きが変化し、キラリティによって二軸性光学異性体として振る舞うようにする。このようにして実施例6の回折格子7を実現することができる。
この実施例6の回折格子7は、二軸性光学異方性を有する液晶740の配向によって、屈折率が正弦波状に変化し、その屈折率を透明電極710に印加する電圧によって可変とすることが可能な透過型VPH回折格子を実現している。つまり、透明電極710の印加電圧の制御によって、S偏光およびP偏光に対する回折効率の特性を制御することができる。
A method for manufacturing the diffraction grating 7 of Example 6 shown in FIG. 12 will be described below. The lower substrate 700 and the upper substrate 730 are arranged to face each other with a gap having an arbitrary thickness, and the opposing surfaces of the lower substrate 700 and the upper substrate 730 have the same upper and lower lattice periods and an arbitrary duty ratio. A grid of transparent electrodes 710 is arranged. At this time, the transparent electrode 710 provided on the lower substrate 700 side and the transparent electrode 710 provided on the upper substrate 730 side are arranged to face each other. In addition, a liquid crystal alignment film 720 is disposed on the opposite surface (the surface in contact with the liquid crystal) of the lower substrate 700 and the upper substrate 730 and the surface in which the transparent electrode 710 is in contact with the liquid crystal. Next, a liquid crystal 740 is filled in a gap between the lower substrate 700 and the upper substrate 730. Since the liquid crystal 740 is ferroelectric, it exhibits biaxial optical anisotropy due to spontaneous chirality (Chirality: a property in which a three-dimensional figure or object cannot be superimposed on its mirror image. Palmarity). It is a liquid crystal (banana-type liquid crystal, disk-type liquid crystal, etc.) and is oriented in an arbitrary direction and parallel to the lower substrate 700 and the upper substrate 730 or at an arbitrary pretilt angle. In addition, as shown in the side view of FIG. 12, the major axis of the molecule 750 of the liquid crystal 740 is inclined in the upper and lower electrode directions (direction parallel to the lines of electric force), the chirality disappears, and the molecule 750 of the liquid crystal 740 becomes uniaxial optical. As the distance from the molecules 750 of the liquid crystal 740 located between the transparent electrodes 710 increases, the lower substrate 700 and the upper substrate gradually move from the inclination of the molecules 750 of the liquid crystals 740 located between the upper and lower transparent electrodes 710. The inclination of the liquid crystal 740 changes parallel to the substrate 730 or at a pretilt angle so that it behaves as a biaxial optical isomer due to chirality. In this way, the diffraction grating 7 of Example 6 can be realized.
In the diffraction grating 7 of Example 6, the refractive index changes sinusoidally depending on the orientation of the liquid crystal 740 having biaxial optical anisotropy, and the refractive index is variable depending on the voltage applied to the transparent electrode 710. A transmissive VPH diffraction grating capable of satisfying the above has been realized. That is, the characteristics of the diffraction efficiency for S-polarized light and P-polarized light can be controlled by controlling the voltage applied to the transparent electrode 710.

図13は二軸性異方性の液晶の座標面内を伝搬する光束について電界が座標面と平行に振動する偏光(実線)および垂直に振動する偏光(破線)の入射方位の屈折率を示した。図13の左の図のx−y平面においてx軸に沿って入射する光束はz軸方向に電界が振動する偏光の屈折率がn1、y軸方向に電界が振動する偏光の屈折率がn2であり、y軸に沿って入射する光束はz軸方向に電界が振動する偏光の屈折率がn1、x軸方向に電界が振動する偏光の屈折率がn3あることがわかる。また、中央あるいは右の図より、z軸に沿って入射する光束はx軸方向に電界が振動する偏光の屈折率がn3、y軸方向に電界が振動する偏光の屈折率がn2であることがわかる。
例えば上記二軸性光学異方性の液晶740の分子750の長軸がz軸であり、n1=1.7、n2=1.66、n3=1.5である場合に、液晶配向膜720によって液晶740の分子750の長軸が格子と垂直かつ上下の基板と平行に、またy軸が格子と平行に配向させると、S偏光の屈折率が1.66、P偏光の屈折率が1.7となる。一方、透明電極710の間の液晶740の分子750は透明電極710に電圧を印可すると長軸(z軸)が透明電極710の方向に向いて個々の液晶740の分子750のx軸とy軸はz軸を回転中心にして自由な方向を向いているとすると、S偏光およびP偏光の屈折率はn2とn3の平均値1.58である。すなわち、nSmax=1.66、nSmin=1.58、nPmax=1.7、nPmin=1.58である。式(5)およびスネルの式(2)よりS偏光に対するブラッグ角がθS=23.8°、P偏光に対するブラッグ角がθP=24.1°(真空中のブラッグ角はともにθ0=40.8°)とすると、図7のようにS偏光とP偏光の特性が一致する。
FIG. 13 shows the refractive indices of incident azimuths of polarized light (solid line) whose electric field oscillates parallel to the coordinate plane (broken line) and polarized light (broken line) oscillates perpendicularly to the light beam propagating in the coordinate plane of the liquid crystal having biaxial anisotropy. It was. In the xy plane in the left diagram of FIG. 13, the light beam incident along the x-axis has a refractive index n1 of polarized light whose electric field oscillates in the z-axis direction and a refractive index n2 of polarized light whose electric field oscillates in the y-axis direction. It can be seen that the light beam incident along the y-axis has a refractive index n1 of polarized light whose electric field oscillates in the z-axis direction and a refractive index n3 of polarized light whose electric field oscillates in the x-axis direction. From the center or right figure, the light beam incident along the z-axis has a refractive index n3 of polarized light whose electric field oscillates in the x-axis direction and n2 of polarized light whose electric field oscillates in the y-axis direction. I understand.
For example, when the major axis of the molecule 750 of the liquid crystal 740 having the biaxial optical anisotropy is the z axis, and n1 = 1.7, n2 = 1.66, and n3 = 1.5, the liquid crystal alignment film 720 If the major axis of the molecules 750 of the liquid crystal 740 is aligned perpendicular to the lattice and parallel to the upper and lower substrates, and the y-axis is aligned parallel to the lattice, the refractive index of S-polarized light is 1.66 and the refractive index of P-polarized light is 1. .7. On the other hand, the molecules 750 of the liquid crystal 740 between the transparent electrodes 710 are such that when a voltage is applied to the transparent electrode 710, the major axis (z-axis) faces the direction of the transparent electrode 710 and the x-axis and y-axis of each molecule 750 of the liquid crystal 740. Is oriented in any direction with the z axis as the rotation center, the refractive index of S-polarized light and P-polarized light is the average value of n2 and n3 of 1.58. That is, nSmax = 1.66, nSmin = 1.58, nPmax = 1.7, and nPmin = 1.58. From Equation (5) and Snell's Equation (2), the Bragg angle for S-polarized light is θS = 23.8 ° and the Bragg angle for P-polarized light is θP = 24.1 ° (both Bragg angles in vacuum are θ0 = 40.8). )), The characteristics of S-polarized light and P-polarized light coincide as shown in FIG.

図14に示す実施例7の光導波路8の製作方法を説明する。コア層810の上下をクラッド層800によって挟まれた平面型の光導波路の、コア層810の一部を直線あるいは任意の曲線を描く帯状に除去する。その除去されたコア層810の上下のクラッド層800に上下同一格子周期かつ任意のデューティ比をなす電極830の格子を、上記直線あるいは曲線に垂直あるいは任意の角度をなして略同位相で配置する。また、強誘電性であるために自発的なキラリティによって二軸性光学異方性を発現する液晶840が、任意の方位と上下のクラッド層800に平行あるいは任意のプレティルト角に配向するように、上下のクラッド層800および電極830が液晶840と接する面に液晶配向膜820を配置する。次に、除去されたコア層810部分に液晶840を充填する。以上により実施例7の平面型の光導波路8を製造する。
この光導波路8は、上下の電極830に任意の電圧を印加することによって、図14の正面図のように上下の電極830の間の液晶840が上下の電極方向に配向が傾き、キラリティが消失して液晶840が一軸性光学異性体として振る舞い、電極830の間に位置する液晶840からの距離が離れるに従って電極830の間に位置する液晶840の傾きから徐々にクラッド層800に平行あるいはプレティルト角に液晶840の配向の傾きが変化し、キラリティによって二軸性光学異性体として振る舞う。これにより、屈折率が正弦波状に変調している。つまり、実施例6の回折格子7をコア材とクラッド材により埋め込んだ平面型の構造の光導波路であり、電極830の印加電圧によって、TE波およびTM波の回折効率の特性を制御可能となっている。
A method for manufacturing the optical waveguide 8 of Example 7 shown in FIG. 14 will be described. Part of the core layer 810 of the planar optical waveguide sandwiched between the upper and lower sides of the core layer 810 by the clad layer 800 is removed in a strip shape that draws a straight line or an arbitrary curve. The gratings of the electrodes 830 having the same upper and lower grating periods and an arbitrary duty ratio are arranged on the upper and lower clad layers 800 of the removed core layer 810 in substantially the same phase perpendicular to the straight line or curve or at an arbitrary angle. . In addition, since the liquid crystal 840 that exhibits biaxial optical anisotropy due to spontaneous chirality due to its ferroelectricity is aligned in an arbitrary direction and parallel to the upper and lower cladding layers 800 or in an arbitrary pretilt angle, A liquid crystal alignment film 820 is disposed on the surface where the upper and lower cladding layers 800 and the electrode 830 are in contact with the liquid crystal 840. Next, liquid crystal 840 is filled in the removed core layer 810 portion. As described above, the planar optical waveguide 8 of Example 7 is manufactured.
In this optical waveguide 8, by applying an arbitrary voltage to the upper and lower electrodes 830, the liquid crystal 840 between the upper and lower electrodes 830 is tilted in the upper and lower electrode directions as shown in the front view of FIG. The liquid crystal 840 behaves as a uniaxial optical isomer, and gradually becomes parallel to the cladding layer 800 or pretilt angle from the inclination of the liquid crystal 840 positioned between the electrodes 830 as the distance from the liquid crystal 840 positioned between the electrodes 830 increases. The tilt of the orientation of the liquid crystal 840 changes, and it behaves as a biaxial optical isomer due to chirality. Thereby, the refractive index is modulated in a sine wave shape. That is, the optical waveguide has a planar structure in which the diffraction grating 7 of Example 6 is embedded with a core material and a cladding material, and the diffraction efficiency characteristics of the TE wave and the TM wave can be controlled by the voltage applied to the electrode 830. ing.

図15に示す実施例8の回折格子9の製作方法を説明する。透明な基板900上に透明電極910を配置する。その上にフォトリソグラフィ技術等によって、樹脂やガラス等の光学等方性媒質の層を形成した後、断面が矩形のストライプ状の溝940を形成して、深い矩形格子930を形成する。溝940の幅はw1、矩形格子930の幅はw2である。溝940の底部に任意の方位と透明基板900に平行あるいは任意のプレティルト角に液晶を配向させる液晶配向膜920を配置する。そして、溝940に液晶960を充填し、透明電極910が配置された透明な基板950を、その透明電極910側を液晶960に向けて配置することで、液晶960を封止する。以上により、実施例8の回折格子9を製造することができる。
この回折格子9は、実施例3の回折格子5において、光学異方性媒質として液晶を用い、液晶の分子の配向を電圧印加によって制御することで、S偏光およびP偏光の回折効率の特性を可変としたものである。例えば液晶960を一軸性の液晶とする場合に、常光線屈折率を光学等方性媒質の屈折率と一致させておき、無電界においては式(8)あるいは式(9)を満足する屈折率になるように所望の方位に液晶を配向させておき、透明電極910に電圧を印可した場合においては、液晶960の分子の長軸が透明電極910の方位に配向することによって、図11のようにS偏光とP偏光ともに最大100%の回折効率を達成する回折格子から、素通しの窓に切り替えることができる。
A method for manufacturing the diffraction grating 9 of Example 8 shown in FIG. 15 will be described. A transparent electrode 910 is disposed on a transparent substrate 900. A layer of an optically isotropic medium such as resin or glass is formed thereon by a photolithography technique or the like, and then a stripe-shaped groove 940 having a rectangular cross section is formed to form a deep rectangular lattice 930. The width of the groove 940 is w1, and the width of the rectangular lattice 930 is w2. A liquid crystal alignment film 920 that aligns liquid crystal in an arbitrary orientation and parallel to the transparent substrate 900 or in an arbitrary pretilt angle is disposed at the bottom of the groove 940. Then, the liquid crystal 960 is sealed by filling the groove 940 with the liquid crystal 960 and disposing the transparent substrate 950 on which the transparent electrode 910 is disposed with the transparent electrode 910 side facing the liquid crystal 960. Thus, the diffraction grating 9 of Example 8 can be manufactured.
This diffraction grating 9 uses the liquid crystal as the optically anisotropic medium in the diffraction grating 5 of the third embodiment, and controls the orientation of the liquid crystal molecules by applying a voltage, thereby improving the diffraction efficiency characteristics of S-polarized light and P-polarized light. It is variable. For example, when the liquid crystal 960 is a uniaxial liquid crystal, the ordinary ray refractive index is made to coincide with the refractive index of the optical isotropic medium, and the refractive index satisfying the formula (8) or the formula (9) in the absence of an electric field. In the case where the liquid crystal is aligned in a desired direction and a voltage is applied to the transparent electrode 910, the long axes of the molecules of the liquid crystal 960 are aligned in the direction of the transparent electrode 910, as shown in FIG. In addition, it is possible to switch from a diffraction grating that achieves diffraction efficiency up to 100% for both S-polarized light and P-polarized light to a plain window.

図16に示す実施例9の光導波路10の製作方法を説明する。まず、クラッド層1000上に電極1030を形成し、さらに電極1030上にコア層1010を形成する。次に、コア層1010の一部を直線あるいは任意の曲線を描く帯状に配列された浅い短冊状の溝1040を形成し、矩形格子1050を形成する。次に、溝1040の底部に液晶が任意の方位とクラッド層に平行あるいは任意のプレティルト角に配向するよう液晶配向膜1020を配置する。そして、溝1040に液晶1060を充填し、電極1030と液晶配向膜1020が形成されたクラッド層1010を、その液晶配向膜1020側を液晶1060に向けてコア層1010に接触させて液晶1060を封止する。以上によって実施例9の光導波路10を製造することができる。
この実施例9の光導波路10は、電極1030に電圧を印加することによって、液晶1060が上下の電極方向に任意の角度で傾くので、屈折率を変化させることができ、その結果、TE波およびTM波の回折効率の特性を制御可能である。
A method for manufacturing the optical waveguide 10 of Example 9 shown in FIG. 16 will be described. First, the electrode 1030 is formed on the cladding layer 1000, and the core layer 1010 is further formed on the electrode 1030. Next, a shallow strip-shaped groove 1040 arranged in a strip shape drawing a straight line or an arbitrary curve is formed on a part of the core layer 1010, and a rectangular lattice 1050 is formed. Next, a liquid crystal alignment film 1020 is disposed at the bottom of the groove 1040 so that the liquid crystal is aligned in an arbitrary orientation and parallel to the cladding layer or in an arbitrary pretilt angle. Then, the liquid crystal 1060 is filled in the groove 1040, and the cladding layer 1010 on which the electrode 1030 and the liquid crystal alignment film 1020 are formed is brought into contact with the core layer 1010 with the liquid crystal alignment film 1020 side facing the liquid crystal 1060, thereby sealing the liquid crystal 1060. Stop. Thus, the optical waveguide 10 of Example 9 can be manufactured.
In the optical waveguide 10 of the ninth embodiment, by applying a voltage to the electrode 1030, the liquid crystal 1060 tilts at an arbitrary angle in the upper and lower electrode directions, so that the refractive index can be changed. The characteristics of TM wave diffraction efficiency can be controlled.

本発明の回折格子3、光導波路4、回折格子7、光導波路8は、式(5)または、式(6)や式(7)が等式である条件から概ね±10%の偏差であれば多くの場合に実用上問題なく利用できる。   The diffraction grating 3, the optical waveguide 4, the diffraction grating 7, and the optical waveguide 8 according to the present invention should have a deviation of approximately ± 10% from the condition that the equation (5) or the equations (6) and (7) are equal. In many cases, it can be used without any practical problem.

本発明の回折格子5、光導波路6、回折格子9、光導波路10は、式(8)や式(9)または、式(10)や式(11)、式(12)、式(13)が等式である条件から概ね±10%の偏差であれば多くの場合に実用上問題なく利用できる。   The diffraction grating 5, the optical waveguide 6, the diffraction grating 9, and the optical waveguide 10 according to the present invention have the formula (8), the formula (9), the formula (10), the formula (11), the formula (12), and the formula (13). If the deviation is approximately ± 10% from the condition that is an equation, it can be used practically without problems.

本発明の回折格子5、光導波路6、回折格子9、光導波路10は、それらの素子に用いている光学等方性媒質の代わりに、それらの素子に用いている光学異方性媒質とは異なる特性の光学異方性媒質を組み合せた矩形格子であっても良い。   The diffraction grating 5, the optical waveguide 6, the diffraction grating 9, and the optical waveguide 10 according to the present invention are different from the optically isotropic medium used in these elements, and the optical anisotropic medium used in these elements is A rectangular grating combining optically anisotropic media having different characteristics may be used.

本発明の回折格子5、光導波路6、回折格子9、光導波路10は、S偏光(TE波)の屈折率とP偏光(TM波)の屈折率の調節による偏光回折効率特性の調整の効果と非特許文献6のようなデューティ比の調節によるS偏光(TE波)とP偏光(TM波)の偏光回折効率特性の調整の効果を組み合わせても良い。   The diffraction grating 5, the optical waveguide 6, the diffraction grating 9, and the optical waveguide 10 of the present invention have the effect of adjusting the polarization diffraction efficiency characteristics by adjusting the refractive index of S-polarized light (TE wave) and the refractive index of P-polarized light (TM wave). And the effect of adjusting the polarization diffraction efficiency characteristics of S-polarized light (TE wave) and P-polarized light (TM wave) by adjusting the duty ratio as in Non-Patent Document 6 may be combined.

以上、本発明の実施例について詳細に説明したが、これらは例示に過ぎず、特許請求の範囲を限定するものではない。特許請求の範囲に記載の技術には、以上に例示した具体例を様々に変形、変更したものが含まれる。   As mentioned above, although the Example of this invention was described in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

本明細書または図面に説明した技術要素は、単独であるいは各種の組合せによって技術的有用性を発揮するものであり、出願時請求項記載の組合せに限定されるものではない。また、本明細書または図面に例示した技術は複数目的を同時に達成し得るものであり、そのうちの一つの目的を達成すること自体で技術的有用性を持つものである。   The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

本発明の回折格子および光導波路は、従来の表面刻線型回折格子やVPH回折格子、厚い透過型矩形回折格子と比べて、高い回折効率と大きな波長分散、広い波長帯域を同時に実現可能であるために、ラマン散乱やトムソン散乱、生体等の蛍光、天文学観測等の微弱光の分光計測装置をはじめ、各種光計測器に利用されることによって測定限界の向上や大幅な計測時間の短縮等が可能になる。   The diffraction grating and optical waveguide of the present invention can simultaneously realize high diffraction efficiency, large wavelength dispersion, and a wide wavelength band, compared to conventional surface-stitched diffraction gratings, VPH diffraction gratings, and thick transmission rectangular diffraction gratings. In addition, it can be used in various optical measuring instruments such as Raman scattering, Thomson scattering, fluorescence of living organisms, and faint light spectroscopic measurement devices such as astronomical observation, etc., which can improve the measurement limit and greatly shorten the measurement time. become.

本発明の回折格子3およびは回折格子5の光学異方性媒質として硬化型の液晶を採用することにより、液晶フラット・ディスプレイ等と同様の製造工程によってメートルクラスのサイズの回折光学素を低価格で製作が可能である。メートルクラスの大面積回折格子が実用化されれば、大型ヘッドアップディスプレイや3次元映像用大型ディスプレイ、外光を天井や部屋の奥に導いて照明として利用する省エネ窓等の応用が可能になる。   By adopting a curable liquid crystal as the optically anisotropic medium of the diffraction grating 3 and the diffraction grating 5 of the present invention, a diffractive optical element of a metric class size can be manufactured at a low cost by the same manufacturing process as a liquid crystal flat display or the like. Can be produced. If a meter-class large-area diffraction grating is put to practical use, it will be possible to apply large head-up displays, large-sized displays for 3D images, energy-saving windows that guide outside light to the ceiling or the back of the room and use it as lighting. .

本発明の回折格子7および回折格子9は、光学異方性媒質として液晶を採用し、格子の両面に透明電極を配置することにより、任意の偏光回折効率特性から任意の偏光回折効率特性に切り換えることが可能な効率が高い能動的な回折光学素子を実現できる。このような光学素子は偏光分光計測装置等の光計測装置や光情報処理、光コンピューティング等に利用可能である。また、上記の大型ヘッドアップディスプレイや3次元映像用大型ディスプレイ、外光導入窓に利用した場合に調光が可能になる。   The diffraction grating 7 and the diffraction grating 9 of the present invention employ a liquid crystal as an optically anisotropic medium, and arrange transparent electrodes on both sides of the grating, thereby switching from an arbitrary polarization diffraction efficiency characteristic to an arbitrary polarization diffraction efficiency characteristic. It is possible to realize an active diffractive optical element with high efficiency. Such an optical element can be used for an optical measuring device such as a polarization spectroscopic measuring device, optical information processing, optical computing, and the like. In addition, dimming is possible when used for the large head-up display, the large display for 3D video, and the external light introduction window.

本発明の光導波路8および光導波路10は設置された矩形格子の光学異方性媒質として溝に液晶を任意の方位に配向させて充填し、平面光導波路の上下に電極を配置することにより、任意の偏光回折効率特性から任意の偏光回折効率特性に切り換えることが可能な効率が高い能動的な回折光学素子を実現できる。このような光学素子は光通信や光情報処理、光コンピューティング等に利用可能である。   The optical waveguide 8 and the optical waveguide 10 of the present invention are filled with a liquid crystal oriented in an arbitrary direction as an optically anisotropic medium having a rectangular lattice, and electrodes are arranged above and below the planar optical waveguide, An active diffractive optical element with high efficiency that can be switched from an arbitrary polarization diffraction efficiency characteristic to an arbitrary polarization diffraction efficiency characteristic can be realized. Such an optical element can be used for optical communication, optical information processing, optical computing, and the like.

1 透過型VPH回折格子
2 厚い透過型矩形回折格子
3、5、7、9 回折格子
4、6、8、10 光導波路
20、230 ホログラム樹脂
21、22、450、520 光学等方性媒質
30、40、200、240、400、430、900、950 基板
700 下基板
730 上基板
210 液晶性有機材料
220 熱硬化型樹脂材料
300、500、800、1000 クラッド層
310、510、810、1010 コア層
410、940、1040 溝
420、930、1050 矩形格子
530 光学異方性媒質
710、910 透明電極
720、820、920、1020 液晶配向膜
740、840、960、1060 液晶
750 液晶の分子
830、1030 電極
DESCRIPTION OF SYMBOLS 1 Transmission type VPH diffraction grating 2 Thick transmission type rectangular diffraction grating 3, 5, 7, 9 Diffraction gratings 4, 6, 8, 10 Optical waveguide 20, 230 Hologram resin 21, 22, 450, 520 Optical isotropic medium 30, 40, 200, 240, 400, 430, 900, 950 Substrate 700 Lower substrate 730 Upper substrate 210 Liquid crystalline organic material 220 Thermosetting resin material 300, 500, 800, 1000 Clad layer 310, 510, 810, 1010 Core layer 410 , 940, 1040 Groove 420, 930, 1050 Rectangular grating 530 Optical anisotropic medium 710, 910 Transparent electrode 720, 820, 920, 1020 Liquid crystal alignment film 740, 840, 960, 1060 Liquid crystal 750 Liquid crystal molecule 830, 1030 Electrode

Claims (12)

屈折率が正弦波状に変調された格子構造である透過型VPH回折格子であって、
光学異方性媒質を用い、所望の波長、および所望のブラッグ角に対して、
S偏光に対する最大屈折率をnSmax、最小屈折率をnSmin、P偏光に対する最大屈折率をnPmax、最小屈折率をnPminとして、
nSmax、nSmin、nPmax、およびnPminは、
(nSmax−nSmin)/cosθSと、(nPmax−nPmin)*cos2θP/cosθPとが、10%以内の違いとなるように、それらの値が設定され、これにより、S偏光の回折効率の厚さ依存特性における周期と、P偏光の回折効率の厚さ依存特性における周期との差が10%以内となるように一致させ、
さらに、回折格子の厚さは、上記設定されたS偏光の回折効率の前記厚さ依存特性、およびP偏光の回折効率の前記厚さ依存特性に基づき、S偏光の回折効率とP偏光の回折効率の平均が90%以上となるように設定されている、
ことを特徴とする回折格子。
ただし、上記式においてθSはS偏光に対するブラッグ角、θPはP偏光に対するブラッグ角である。
A transmissive VPH diffraction grating having a grating structure with a refractive index modulated in a sinusoidal shape,
Using an optically anisotropic medium, for a desired wavelength and a desired Bragg angle,
The maximum refractive index for S-polarized light is nSmax, the minimum refractive index is nSmin, the maximum refractive index for P-polarized light is nPmax, and the minimum refractive index is nPmin.
nSmax, nSmin, nPmax, and nPmin are
(NSmax−nSmin) / cos θS and (nPmax−nPmin) * cos 2θP / cos θP are set so that the difference is within 10%, and thereby the thickness dependence of the diffraction efficiency of S-polarized light and the period of the characteristic, match as a difference between the period in the thickness dependence of the diffraction efficiency of the P polarized light is within 10%,
Further, the thickness of the diffraction grating, the thickness dependence of the diffraction efficiency of the set S-polarized light, and on the basis of the thickness dependence of the diffraction efficiency of the P-polarized light, the diffraction of the S-polarized light of the diffraction efficiency and P-polarized light The average efficiency is set to be 90% or more,
A diffraction grating characterized by that.
In the above equation, θS is the Bragg angle for S-polarized light, and θP is the Bragg angle for P-polarized light.
前記回折格子は、光学等方性の樹脂に、所定の方向に配向した光学異方性の液晶が混合された樹脂であり、
前記樹脂中の前記液晶の濃度によって屈折率が正弦波状に変調され、
前記液晶の濃度および液晶分子の配向方向によって、S偏光に対する最大屈折率と最小屈折率との差と、P偏光に対する最大屈折率と最小屈折率との差とを、異なる所定値としたことを特徴とする請求項1に記載の回折格子。
The diffraction grating is a resin in which an optically isotropic resin is mixed with an optically anisotropic liquid crystal oriented in a predetermined direction,
The refractive index is modulated in a sinusoidal shape by the concentration of the liquid crystal in the resin,
The difference between the maximum refractive index and the minimum refractive index for S-polarized light and the difference between the maximum refractive index and the minimum refractive index for P-polarized light are set to different predetermined values depending on the concentration of liquid crystal and the orientation direction of liquid crystal molecules. The diffraction grating according to claim 1, wherein:
前記回折格子は、
二軸性光学異方性の液晶と、
前記液晶を挟んでその液晶に接し、前記液晶を所定の方向に配向させる液晶配向膜と、
前記液晶を挟む1対の電極が周期的に配置された電極部と、
を有し、
前記電極部への電圧の印加によって前記液晶分子の配向方向を制御することにより、前記液晶の屈折率を正弦波状に変調し、かつ、S偏光に対する最大屈折率と最小屈折率との差と、P偏光に対する最大屈折率と最小屈折率との差とを異なる所定値とし、
前記電極部への印加電圧値を変えることで、S偏光の回折効率とP偏光の回折効率とを可変としたことを特徴とする請求項1に記載の回折格子。
The diffraction grating is
A biaxial optically anisotropic liquid crystal;
A liquid crystal alignment film in contact with the liquid crystal with the liquid crystal sandwiched therebetween, and aligning the liquid crystal in a predetermined direction;
An electrode portion in which a pair of electrodes sandwiching the liquid crystal is periodically arranged;
Have
By controlling the orientation direction of the liquid crystal molecules by applying a voltage to the electrode portion, the refractive index of the liquid crystal is modulated in a sinusoidal shape, and the difference between the maximum refractive index and the minimum refractive index for S-polarized light, The difference between the maximum refractive index and the minimum refractive index for P-polarized light is set to a different predetermined value.
The diffraction grating according to claim 1, wherein the diffraction efficiency of S-polarized light and the diffraction efficiency of P-polarized light are made variable by changing a voltage value applied to the electrode section.
2種類の屈折率が異なる材料が交互に周期的に配置された矩形格子構造である透過型の回折格子であって、
2種類の材料のうち一方が光学異方性媒質、他方が光学等方性媒質であり、所望の波長および所望のブラッグ角に対して、
前記光学異方性媒質のS偏光に対する最大屈折率をn2cS、P偏光に対する最大屈折率をn2cPとし、前記光学等方性媒質の屈折率をn2aとして、n2a、n2cS、およびn2cPは、
n2cP>n2cS>n2aまたはn2cP<n2cS<n2aの場合には、A1*(n2cS−n2a)/cosθSと、B1*(n2cP−n2a)*cos2θP/cosθPとが、
n2cP>n2a>n2cSまたはn2cP<n2a<n2cSの場合には、A2*(n2cS−n2a)/cosθSと、−B2*(n2cP−n2a)*cos2θP/cosθPとが、10%以内の違いとなるように、それらの値が設定され、これにより、S偏光の回折効率の厚さ依存特性における周期と、P偏光の回折効率の厚さ依存特性における周期との差が10%以内となるように一致させ、
さらに、回折格子の厚さは、上記設定されたS偏光の回折効率の前記厚さ依存特性、およびP偏光の回折効率の前記厚さ依存特性に基づき、S偏光の回折効率とP偏光の回折効率の平均が90%以上となるように設定されている、
ことを特徴とする回折格子。
ただし、上記式においてθSはS偏光に対するブラッグ角、θPはP偏光に対するブラッグ角である。また、A1、A2はRCWA法によって求めた前記回折格子のS偏光の回折効率の前記厚さ依存特性における波数(1/周期)を、2波結合解析法によって求めた透過型VPH回折格子のS偏光の回折効率の前記厚さ依存特性における波数(1/周期)で割った値である。また、B1B2はRCWA法によって求めた前記回折格子のP偏光の回折効率の前記厚さ依存特性における波数(1/周期)を2波結合解析法によって求めた透過型VPH回折格子のP偏光の回折効率の前記厚さ依存特性における波数(1/周期)で割った値である。また、上記の透過型VPH回折格子とは、S偏光に対する最大屈折率をn2cS、n2aのうち大きい方、最小屈折率をn2cS、n2aのうち小さい方とし、P偏光に対する最大屈折率をn2cP、n2aのうち大きい方、最小屈折率をn2cP、n2aのうち小さい方とした透過型VPH回折格子である。
A transmission type diffraction grating having a rectangular grating structure in which two kinds of materials having different refractive indexes are alternately and periodically arranged,
One of the two types of materials is an optically anisotropic medium and the other is an optically isotropic medium. For a desired wavelength and a desired Bragg angle,
The maximum refractive index for the S-polarized light of the optically anisotropic medium is n2cS, the maximum refractive index for the P-polarized light is n2cP, and the refractive index of the optical isotropic medium is n2a, and n2a, n2cS, and n2cP are:
In the case of n2cP>n2cS> n2a or n2cP <n2cS <n2a, A1 * (n2cS−n2a) / cosθS and B1 * (n2cP−n2a) * cos2θP / cosθP
When n2cP>n2a> n2cS or n2cP <n2a <n2cS, A2 * (n2cS−n2a) / cosθS and −B2 * (n2cP−n2a) * cos2θP / cosθP should be within 10%. a is the values are set, thereby matching as the difference between the period in the thickness dependence of the diffraction efficiency of the S polarized light, and the period in the thickness dependence of the diffraction efficiency of the P polarized light is within 10% Let
Further, the thickness of the diffraction grating, the thickness dependence of the diffraction efficiency of the set S-polarized light, and on the basis of the thickness dependence of the diffraction efficiency of the P-polarized light, the diffraction of the S-polarized light of the diffraction efficiency and P-polarized light The average efficiency is set to be 90% or more,
A diffraction grating characterized by that.
In the above equation, θS is the Bragg angle for S-polarized light, and θP is the Bragg angle for P-polarized light. Further, A1 and A2 are the wave numbers (1 / periods) in the thickness- dependent characteristics of the diffraction efficiency of the S-polarized light of the diffraction grating obtained by the RCWA method, and the S of the transmission type VPH diffraction grating obtained by the two-wave coupling analysis method. it is divided by the wave number (1 / period) in the thickness dependence of the diffraction efficiency of the polarization. Also, B1, B2 is P-polarized light transmission VPH grating determined by the two-wave coupling analysis the wave number (1 / period) in the thickness dependence of the diffraction efficiency of the P polarized light of the diffraction grating obtained by RCWA method the diffraction efficiency of which is divided by the wave number (1 / period) in thickness dependent properties. The transmission type VPH diffraction grating described above has a maximum refractive index for S-polarized light of n2cS and n2a, a minimum refractive index of n2cS and n2a, and a maximum refractive index for P-polarized light of n2cP and n2a. Is a transmission type VPH diffraction grating having a larger one of n2cP and a smaller refractive index of n2a.
格子状の溝が設けられた光学異方性材料からなる基板と、前記基板の前記溝を埋める光学等方性材料と、によって構成されていることを特徴とする請求項4に記載の回折格子。   5. The diffraction grating according to claim 4, comprising a substrate made of an optically anisotropic material provided with a grating-like groove, and an optically isotropic material filling the groove of the substrate. . 前記基板は、β−メタホウ酸バリウム(β−BaB2O4:β−BBO)、フッ化イットリウム−リチウム(YLiF4:YLF)、またはニオブ酸リチウム(LiNbO3)からなる結晶、ないしは、延伸された樹脂、または配向された状態で硬化した液晶である、ことを特徴とする請求項5に記載の回折格子。   The substrate is a crystal or stretched resin or orientation of β-barium metaborate (β-BaB2O4: β-BBO), yttrium fluoride-lithium (YLiF4: YLF), or lithium niobate (LiNbO3). The diffraction grating according to claim 5, wherein the diffraction grating is a liquid crystal cured in a finished state. 格子状の溝が設けられた光学等方性材料からなる基板と、前記溝を埋める所定の方向に配向した状態で硬化された液晶と、によって構成されていることを特徴とする請求項4に記載の回折格子。   5. The substrate according to claim 4, wherein the substrate is made of an optically isotropic material provided with a lattice-shaped groove, and a liquid crystal is cured in a state of being oriented in a predetermined direction filling the groove. The diffraction grating described. 格子状の溝が設けられた光学等方性材料からなる第1基板と、
前記第1基板の溝に充填された液晶と、
前記第1基板上に配置され、前記液晶に接し、前記液晶を所定の方向に配向させる液晶配向膜が設けられた第2基板と、
前記第1基板の各前記溝の底面と、前記第2基板の前記第1基板側表面であって前記溝に対向する位置と、に設けられた電極部と、
を有し、
前記電極部への電圧の印加によって前記液晶の分子の配向方向を制御することにより、S偏光に対する屈折率と、P偏光に対する屈折率とを異なる所定値とし、
前記電極部への印加電圧値を変えることで、S偏光の回折効率とP偏光の回折効率とを可変としたことを特徴とする請求項4に記載の回折格子。
A first substrate made of an optically isotropic material provided with a lattice-shaped groove;
A liquid crystal filled in the groove of the first substrate;
A second substrate provided on the first substrate and provided with a liquid crystal alignment film that contacts the liquid crystal and aligns the liquid crystal in a predetermined direction;
An electrode portion provided on a bottom surface of each groove of the first substrate and a position on the first substrate side surface of the second substrate facing the groove;
Have
By controlling the orientation direction of the molecules of the liquid crystal by applying a voltage to the electrode unit, the refractive index for S-polarized light and the refractive index for P-polarized light are different from each other, and
5. The diffraction grating according to claim 4, wherein the diffraction efficiency of S-polarized light and the diffraction efficiency of P-polarized light are made variable by changing a voltage value applied to the electrode section.
前記回折格子の厚さは、上記設定されたS偏光の回折効率の厚さ依存特性、またはP偏光の回折効率の厚さ依存特性の極大値のうち、最初の極大値近傍を取る厚さに設定されている、ことを特徴とする請求項1ないし請求項8のいずれか1項に記載の回折格子。 The thickness of the diffraction grating, the thickness dependence of the diffraction efficiency of the set S-polarized light or of the maximum value of the thickness dependence of the diffraction efficiency of the P-polarized light, the thickness take the first local maximum near The diffraction grating according to claim 1, wherein the diffraction grating is set. 請求項1ないし請求項9のいずれか1項に記載の回折格子を、格子周期方向に伸びる直線状または曲線状とし、その回折格子がコア材およびクラッド材に埋め込まれた構造であることを特徴とする光導波路。   The diffraction grating according to any one of claims 1 to 9, wherein the diffraction grating has a linear or curved shape extending in a grating period direction, and the diffraction grating is embedded in a core material and a cladding material. An optical waveguide. 屈折率が正弦波状に変調された格子構造である透過型VPH回折格子の設計方法であって、
光学異方性媒質を用い、所望の波長、および所望のブラッグ角に対して、
S偏光に対する最大屈折率をnSmax、最小屈折率をnSmin、P偏光に対する最大屈折率をnPmax、最小屈折率をnPminとして、
nSmax、nSmin、nPmax、およびnPminを、
(nSmax−nSmin)/cosθSと、(nPmax−nPmin)*cos2θP/cosθPとが、10%以内の違いとなるように、それらの値を設定し、これにより、S偏光の回折効率の厚さ依存特性における周期と、P偏光の回折効率の厚さ依存特性における周期との差が10%以内となるように一致させ、
さらに、回折格子の厚さを、上記設定されたS偏光の回折効率の前記厚さ依存特性、およびP偏光の回折効率の前記厚さ依存特性に基づき、S偏光の回折効率とP偏光の回折効率の平均が90%以上となるように設定する、
ことを特徴とする回折格子の設計方法。
ただし、上記式においてθSはS偏光に対するブラッグ角、θPはP偏光に対するブラッグ角である。
A method of designing a transmissive VPH diffraction grating having a grating structure with a refractive index modulated in a sinusoidal shape,
Using an optically anisotropic medium, for a desired wavelength and a desired Bragg angle,
The maximum refractive index for S-polarized light is nSmax, the minimum refractive index is nSmin, the maximum refractive index for P-polarized light is nPmax, and the minimum refractive index is nPmin.
nSmax, nSmin, nPmax, and nPmin,
These values are set so that (nSmax−nSmin) / cos θS and (nPmax−nPmin) * cos 2θP / cos θP are within 10%, and thus the thickness dependence of the diffraction efficiency of S-polarized light The period in the characteristic and the period in the thickness-dependent characteristic of the diffraction efficiency of P-polarized light are matched so as to be within 10%,
Further, the thickness of the diffraction grating, the thickness dependence of the diffraction efficiency of the set S-polarized light, and on the basis of the thickness dependence of the diffraction efficiency of the P-polarized light, the diffraction of the S-polarized light of the diffraction efficiency and P-polarized light Set the average efficiency to be 90% or more,
A method for designing a diffraction grating.
In the above equation, θS is the Bragg angle for S-polarized light, and θP is the Bragg angle for P-polarized light.
2種類の屈折率が異なる材料が交互に周期的に配置された矩形格子構造である透過型の回折格子の設計方法であって、
2種類の材料のうち一方が光学異方性媒質、他方が光学等方性媒質であり、所望の波長および所望のブラッグ角に対して、
前記光学異方性媒質のS偏光に対する最大屈折率をn2cS、P偏光に対する最大屈折率をn2cPとし、前記光学等方性媒質の屈折率をn2aとして、n2a、n2cS、およびn2cPを、
n2cP>n2cS>n2aまたはn2cP<n2cS<n2aの場合には、A1*(n2cS−n2a)/cosθSと、B1*(n2cP−n2a)*cos2θP/cosθPとが、
n2cP>n2a>n2cSまたはn2cP<n2a<n2cSの場合には、A2*(n2cS−n2a)/cosθSと、−B2*(n2cP−n2a)*cos2θP/cosθPとが、10%以内の違いとなるように、それらの値を設定し、これにより、S偏光の回折効率の厚さ依存特性における周期と、P偏光の回折効率の厚さ依存特性における周期との差が10%以内となるように一致させ、
さらに、回折格子の厚さを、上記設定されたS偏光の回折効率の前記厚さ依存特性、およびP偏光の回折効率の前記厚さ依存特性に基づき、S偏光の回折効率とP偏光の回折効率の平均が90%以上となるように設定する、
ことを特徴とする回折格子の設計方法。
ただし、上記式においてθSはS偏光に対するブラッグ角、θPはP偏光に対するブラッグ角である。また、A1、A2はRCWA法によって求めた前記回折格子のS偏光の回折効率の前記厚さ依存特性における波数(1/周期)を、2波結合解析法によって求めた透過型VPH回折格子のS偏光の回折効率の前記厚さ依存特性における波数(1/周期)で割った値である。また、B1B2はRCWA法によって求めた前記回折格子のP偏光の回折効率の前記厚さ依存特性における波数(1/周期)を2波結合解析法によって求めた透過型VPH回折格子のP偏光の回折効率の前記厚さ依存特性における波数(1/周期)で割った値である。また、上記の透過型VPH回折格子とは、S偏光に対する最大屈折率をn2cS、n2aのうち大きい方、最小屈折率をn2cS、n2aのうち小さい方とし、P偏光に対する最大屈折率をn2cP、n2aのうち大きい方、最小屈折率をn2cP、n2aのうち小さい方とした透過型VPH回折格子である。
A method of designing a transmission type diffraction grating having a rectangular grating structure in which two kinds of materials having different refractive indexes are alternately and periodically arranged,
One of the two types of materials is an optically anisotropic medium and the other is an optically isotropic medium. For a desired wavelength and a desired Bragg angle,
The maximum refractive index for the S-polarized light of the optically anisotropic medium is n2cS, the maximum refractive index for the P-polarized light is n2cP, the refractive index of the optically isotropic medium is n2a, and n2a, n2cS, and n2cP are
If n2cP>n2cS> n2a or n2cP <n2cS <of n2a is, A1 * and (n2cS-n2a) / cosθS, B1 * and the (n2cP-n2a) * cos2θP / cosθP,
When n2cP>n2a> n2cS or n2cP <n2a <n2cS, A2 * (n2cS−n2a) / cosθS and −B2 * (n2cP−n2a) * cos2θP / cosθP should be within 10%. to, and set their values, thereby matching as the difference between the period in the thickness dependence of the diffraction efficiency of the S polarized light, and the period in the thickness dependence of the diffraction efficiency of the P polarized light is within 10% Let
Further, the thickness of the diffraction grating, the thickness dependence of the diffraction efficiency of the set S-polarized light, and on the basis of the thickness dependence of the diffraction efficiency of the P-polarized light, the diffraction of the S-polarized light of the diffraction efficiency and P-polarized light Set the average efficiency to be 90% or more,
A method for designing a diffraction grating.
In the above equation, θS is the Bragg angle for S-polarized light, and θP is the Bragg angle for P-polarized light. Further, A1 and A2 are the wave numbers (1 / periods) in the thickness-dependent characteristics of the diffraction efficiency of the S-polarized light of the diffraction grating obtained by the RCWA method, and the S of the transmission type VPH diffraction grating obtained by the two-wave coupling analysis method. It is a value obtained by dividing the diffraction efficiency of polarized light by the wave number (1 / period) in the thickness-dependent characteristic . B1 and B2 are the P-polarized light of the transmission type VPH diffraction grating obtained by the two-wave coupling analysis method of the wave number (1 / period) in the thickness-dependent characteristic of the diffraction efficiency of the P-polarized light of the diffraction grating obtained by the RCWA method. It is a value obtained by dividing the diffraction efficiency by the wave number (1 / period) in the thickness-dependent characteristic . The transmission type VPH diffraction grating described above has a maximum refractive index for S-polarized light of n2cS and n2a, a minimum refractive index of n2cS and n2a, and a maximum refractive index for P-polarized light of n2cP and n2a. Is a transmission type VPH diffraction grating having a larger one of n2cP and a smaller refractive index of n2a.
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