JP4164535B2 - Structure using photonic crystal and surface emitting laser - Google Patents

Description

  The present invention relates to a structure using a photonic crystal and a surface emitting laser using the structure.

  Non-Patent Document 1 discusses Guided Resonance using a photonic crystal having the shape shown in FIG.

  Here, 8000 is a sapphire substrate, 8050 is a photonic crystal layer (having holes 8020 periodically formed in GaN 8010), and 8030 is a nucleation layer (AlN).

  Guided resonance means that light in a guided mode guided in the in-plane direction of a photonic crystal having a refractive index periodic structure in the in-plane direction is coupled to the radiation mode, and is emitted outside the photonic crystal. To be done.

  By using this Guided Resonance, the photonic crystal can be used as a mirror. That is, light incident in the direction perpendicular to the plane of the photonic crystal is combined with a mode positioned above the light line, thereby being converted into a mode that guides through the photonic crystal. Thereafter, the light is emitted to the outside of the photonic crystal again by being coupled to the radiation mode. Then, a unique reflection phenomenon, for example, reflection with an efficiency of 100%, occurs due to interference between light reflected directly without being coupled to the waveguide mode and light once coupled to the waveguide mode and radiated to the outside again.

  In general, the waveguide mode refers to a mode that satisfies the condition that light does not leak from the photonic crystal layer, and the radiation mode refers to a mode in which light leaks from the photonic crystal layer.

  The light line indicates a dispersion relation of light propagating in a medium adjacent to the waveguide layer (in this case, the photonic crystal layer). This light line can be represented by a straight line determined by w = ck / n (w: angular frequency, c: speed of light, n: refractive index, k: wave number). In general, a region having a frequency higher than that of a light line is a region where light easily leaks from the photonic crystal.

  As described above, the mirror using the Guided Resonance has a different operating principle from the mirror using the photonic band gap.

  Therefore, when the wavelength of incident light perpendicularly incident on the photonic crystal layer shown in FIG. 8 is adjusted to a wavelength region in which the reflectance is significantly increased by Guided Resonance, the incident light is reflected with a high reflectance. Become.

In the same document, when the refractive index of the sapphire substrate 8000 (refractive index 1.8) adjacent to the photonic crystal layer 8050 (GaN has a refractive index of 2.37) changes, This is considered by simulation.
OPTICS EXPRESS, vol. 13, no. 17, 6564 (2005)

  FIG. 9 shows the Guided that occurs when the refractive index of the photonic crystal layer is fixed and the refractive index on the substrate side (corresponding to n in the figure) is changed with the horizontal axis representing frequency and the vertical axis representing transmittance. It shows the spectrum change of Resonance.

According to FIG. 9, the relative refractive index difference Δn (= (n _phc −n _clad ) / between the photonic crystal layer (refractive index n _phc ) and the substrate (refractive index n _clad ) functioning as the cladding layer adjacent thereto. As n _phc ) becomes smaller, it can be seen that guided resonance is less likely to occur.

Specifically, in the case of n _phc = 2.37 and n _clad = 1.8 (n in FIG. 9 corresponds to n _clad ), the relative refractive index difference between them is about 0.24 (about 24 %). In this case, as can be seen from FIG. 9, a Guided Resonance may occur.

However, when n _phc = 2.37 and n _clad = 2.135, that is, when the relative refractive index difference between the two becomes about 0.10 (about 10%) or less, it is understood that a guided resonance is less likely to occur.

  By the way, considering that a mirror using guided resonance in a photonic crystal is applied to a laser or the like, a case where the difference in refractive index between the photonic crystal layer and the adjacent cladding layer is inevitably set is unavoidable. There is.

  For example, when it is desired to secure a difference in refractive index between a photonic crystal layer and a material adjacent to the photonic crystal layer, air having a low refractive index may be adjacent to the photonic crystal. However, such a so-called air gap structure is difficult to produce by a semiconductor lamination process. Therefore, when considering application to an optical device, a configuration that generates guided resonance is desired even when a semiconductor material having a refractive index larger than that of air is adjacent to the photonic crystal layer.

When a photonic crystal layer is used instead of a multilayer mirror in a surface emitting laser with a wavelength of 670 nm, for example, the following configuration may be adopted. That is, the photonic crystal layer is composed of Al _0.5 Ga _0.5 As (refractive index 3.446), and the cladding layer adjacent to it is Al _0.93 Ga _0.07 As (refractive index 3.130). It is envisaged to configure.

In this case, the relative refractive index difference Δn (= (n _phc -n _clad ) / n _phc ) is about 9.2%. That is, if the configuration described in Non-Patent Document 1 is applied as it is, it is difficult to generate Guided Resonance and it is difficult to use a photonic crystal instead of a multilayer mirror.

  Therefore, the present invention can exhibit Guided Resonance even in a configuration in which a relative refractive index difference between the two is not sufficient, such as GaN 8010 constituting a photonic crystal layer and a sapphire substrate 8000 adjacent thereto. An object of the present invention is to provide a structure and a surface emitting laser using the structure.

A structure having a photonic crystal layer according to the present invention includes a photonic crystal layer in which a plurality of holes are periodically arranged in a first member having a _first refractive index (n ₁ ), and the first A second member having a _second refractive index (n ₂ ) lower than the second refractive index and adjacent to the photonic crystal layer, and greater than 1.0 and greater than the first refractive index. A third member having a low third refractive index (n ₃ ) and formed on the first member, and a relative refraction of the first refractive index and the second refractive index. The rate difference (= (n ₁ −n ₂ ) / n ₁ ) is 0.10 or less, and the depth of the hole provided in the photonic crystal layer is the thickness of the first member. It is characterized by being 20% or more and 80% or less.

  In addition, a surface emitting laser according to the present invention includes a first reflection mirror configured to include the above structure, a second reflection mirror disposed to face the first reflection mirror, and the first reflection mirror. And an active layer disposed between the first reflection mirror and the second reflection mirror.

  According to the present invention, for example, GaN 8010 constituting a photonic crystal layer and a sapphire substrate 8000 adjacent to the photonic crystal layer, a structure capable of exhibiting Guided Resonance even when the relative refractive index difference between the two is not sufficient. It is possible to provide a body and a surface emitting laser using the same.

(First embodiment: structure used as a mirror)
The structure according to this embodiment will be described with reference to FIGS. 1 and 2. FIG. 2 is a cross-sectional view taken along the plane aa ′ in FIG.

In FIG. 1, reference numeral 1000 denotes a photonic crystal layer configured by providing a plurality of holes arranged periodically in a first member (1010 in FIG. 2) having a _first refractive index (n ₁ ). .

Reference numeral 1020 denotes a low refractive index layer as a second member adjacent to the photonic crystal layer 1000 and having a _second refractive index (n ₂ ) lower than the _first refractive index (n ₁ ). is there. This layer is sometimes referred to as a cladding layer.

  The structure according to this embodiment is designed so as to reflect light incident in a direction perpendicular to the plane of the photonic crystal layer 1000 shown in FIG. That is, it is designed to produce a guided resonance with respect to the wavelength of the incident light. In this case, light incident in the direction perpendicular to the plane of the photonic crystal layer 1000 is coupled to a mode guided in the photonic crystal layer, and then emitted to the outside by coupling with a radiation mode. As a result, it functions as a mirror.

Here, the relative refractive index difference Δn (= (n ₁ −n ₂ ) / n ₁ ) between the first refractive index (n ₁ ) and the second refractive index (n ₂ ) is 0.10 or less. is there.

  As described above, when Δn is 0.10 or less, as shown in Non-Patent Document 1, Guided Resonance hardly occurs.

However, in the present embodiment, a third member having a _third refractive index (n ₃ ) having a refractive index larger than 1.0 is formed on the first member.

  As shown in FIG. 2A, as an example in which the third member is formed on the first member 1010, the hole formed in the photonic crystal layer is filled with the third member 1015. There are forms.

When nothing is filled in the holes of the photonic crystal layer, the refractive index of this portion is 1.0, which is the refractive index of air. However, the effective refractive index (n _eff ) of the photonic crystal layer 1000 can be increased by filling the third member having a refractive index larger than 1.0. That is, the difference in refractive index between the photonic crystal layer 1000 and the low refractive index layer 1020 can be increased.

  Moreover, in order to raise the effective refractive index of the photonic crystal layer 1000, it can also comprise as shown in FIG.2 (b). That is, instead of filling the hole 1016, the third member 1017 is formed on the photonic crystal layer 1000. This can also be expressed as the third member 1017 being formed on the first member 1010. Even in such a configuration, the effective refractive index of the photonic crystal layer 1000 can be increased because the incident light is not completely confined in the first member 1010 and propagated, but on both sides thereof. This is because the evanescent wave propagates in a state of exudation.

  The refractive index (third refractive index) of the third member is smaller than the refractive index (first refractive index) of the first member. This is because if the third refractive index is higher than the first refractive index, light cannot be confined in the photonic crystal layer, and guided resonance is less likely to occur.

  Further, as shown in FIG. 2C, the hole is filled with the third member 1015, and another third member 1017 having a refractive index larger than 1.0 is formed on the photonic crystal layer 1000. Providing is also a preferable form in that the effective refractive index can be improved. In such a case, the material constituting the third member 1015 and the other third member 1017 only needs to have a refractive index higher than 1.0, and is not necessarily the same material.

  The photonic crystal layer 1000 is characterized in that the refractive index is periodically different in the in-plane direction. According to the knowledge of the present inventors, when the hole depth is less than 20% with respect to the thickness t of the first member 1010 (slab), the periodicity in the in-plane direction depends on the wavelength. It becomes hard to receive influence based on.

  For example, FIG. 3 is a simulation result of Guided Resonance generated in the configuration shown in FIG. 2C, and the hole depth dependence in FIG. 2C is in the range of 0% to 30% of the slab thickness t. It is calculated. Each corresponds to a depth of (a) 0%, (b) 10%, (c) 20%, (d) 30%. Note that the first member 1010 is a square lattice having a refractive index of 3.446, a low refractive index layer 1020 as a second member of 3.130, and a hole period of 250 nm. The cross-sectional shape of the hole is assumed to be a circle with a radius of 100 nm. The third member 1015 and the other third member 1017 are made of the same material, and the refractive index is 2.0.

  As can be seen from the figure, when the depth of the hole is less than 20% of the slab thickness, the dip in the transmission spectrum becomes small and high reflectivity cannot be obtained.

  Further, when the depth d of the hole exceeds 80% of the slab thickness t with respect to the thickness t of the first member 1010 (slab), it is inconvenient in the following cases.

  When the difference in refractive index between the slab (first member 1010) and the second member constituting the cladding (low refractive index layer 1020) is extremely small, the depth of the hole is increased due to the deep depth of the hole. The volume becomes large. This further reduces the effective refractive index difference between the two. That is, the depth of the hole cannot be deeper than a certain level.

  In this case, when the hole depth d exceeds 80% of the slab thickness t, as shown in FIG. 4, Guided Resonance does not occur. FIG. 4 shows the simulation results when the hole depth is in the range of 70% to 100% of the slab thickness t, as in FIG. These correspond to depths of (a) 70%, (b) 80%, (c) 90%, and (d) 100%, respectively.

  From the above points, it can be seen that the depth d of the hole in the thickness direction of the first member 1010 is preferably 20% or more and 80% or less of the thickness t of the first member.

(First member, second member)
The first refractive index _{n 1} having a first member, for example in the range of 1.2 to 4.0. As a specific _{material, Si, SiO2, SiN, GaAs} , Al x Ga 1-x As, GaN, Al x Ga 1-x N, InP and the like.

The second refractive index n ₂ of the second member is, for example, in the range of 1.0 to 3.8. As a specific _{material, SiO2, SiN, Al x Ga} 1-x As, AlAs, Al x Ga 1-x N, AlN and the like.

As a configuration in which the relative refractive index difference Δn is 0.1 or less, for example, the first member is made of Al _0.5 Ga _0.5 As and the second member is Al _0.93 Ga _0.07 As. To make.

  The shape of the hole provided in the photonic crystal layer is a circle, a square, or the like. In addition, examples of the lattice shape include a square lattice and a triangular lattice.

  The thickness t of the first member is determined in consideration of the waveguide mode of light, manufacturing conditions, and the like. For example, it is in the range of 10 nm to 10 μm.

As the third member, a material having a refractive index larger than 1.0 and lower than the first refractive index of the first member (material having a third refractive index) can be applied. There is no particular limitation as long as it is transparent in the wavelength range of the light used, but specific materials include polystyrene, polyethylene, acrylic resin, epoxy resin, silicone resin, melamine resin, phenol resin, fluororesin, SiN, SiO ₂ , TiO2, ITO, GaO and the like. Of course, the present invention includes the case where the second refractive index and the third refractive index are equal. Note that the third refractive index can be made larger than the second refractive index.

  If the half width of the wavelength in Guided Resonance in Non-Patent Document 1 is estimated, in FIG. 9, each is 2 nm or less. However, in consideration of a process margin when a mirror using Guided Resonance is applied to a device, the half width is preferably wider, specifically, 5 nm or more.

FIG. 6 is a graph showing changes in the half width when the radius r of the hole is gradually increased in order to widen the aforementioned half width when the thickness of the slab is equal to the depth of the hole. . This calculation was performed using the following parameters.
a = 500 nm
t = 750 nm
r = (a) 0.08a, (b) 0.10a, (c) 0.12a, (d) 0.14a
n ₁ = 3.446 (for example, material Al _0.5 Ga _0.5 As) n ₂ = 3.200 (for example, material Al _0.8 Ga _0.2 As)
Here, a is the lattice constant of the photonic crystal layer (corresponding to the period of the square lattice), t is the thickness of the first member (slab), and r is the hole provided in the photonic crystal layer. Radius, n ₁ is the refractive index of the first member, and n ₂ is the refractive index of the second member (cladding layer). In this calculation, the third member is not provided on the first member.

  The relative refractive index difference Δn between the slab and the adjacent cladding layer is about 0.07 (about 7%). By increasing the radius r of the hole, the full width at half maximum can be expanded to about 1 nm (FIG. 6C), but if it is attempted to increase beyond that, the Guided Resonance itself does not occur. (FIG. 6 (d)).

  This is because by increasing the radius of the hole, the volume of the hole increases and the effective refractive index decreases.

In FIG. 7A, the conditions for a, t, n ₁ , and n ₂ are the same as in FIG. 6, and FIG. It is a simulation result when adopting.

Specifically, the radius r of the hole was 200 nm, and the depth d of the hole was 375 nm (that is, 50% of the thickness t of the photonic crystal layer). The refractive index n _{3 of the} material filled in the holes was 1.7 (for example, the material is a thiourethane resin). From this figure, if the structure described in this embodiment is used, the half width of the spectrum can be about 5 nm or more.

  FIGS. 7B and 7C show the configurations of FIGS. 2B and 2C performed under the same conditions as in FIG. 7A. (A), (b), (c) There is no big difference in the spectrum in any configuration, and even if the relative refractive index difference Δn is about 7%, the Guided Resonance phenomenon is generated while keeping the full width at half maximum. I can see that

  In addition, the simulation described above is described in the document Physical Review B, Vol. 68, 155101 (2003).

(Embodiment 2: VCSEL type surface emitting laser)
A vertical cavity surface emitting laser (VCSEL) according to the present embodiment will be described. FIG. 5 schematically shows a cross-sectional view of the configuration of the VCSEL.

  Reference numeral 5050 denotes a substrate, 5000 denotes a lower reflection mirror (for example, a multilayer mirror), 1021 denotes a lower cladding layer, 5900 denotes an active layer, and 5020 denotes an upper cladding layer. Reference numeral 1010 denotes a first member constituting the photonic crystal layer 1000, and reference numeral 1015 denotes a filler as the third member filled in the hole.

  Regarding the photonic crystal layer 1000, the technical matters described in the first embodiment are applied. Note that the upper cladding layer 5020 in this embodiment corresponds to the second member 1020 in the first embodiment. That is, the clad layer 5020 serves as an upper clad layer for the active layer 5900 and as a low refractive index layer for the photonic crystal layer 1000.

  In the VCSEL type surface emitting laser, laser oscillation is realized by resonating and amplifying light generated in the active layer 5900 with upper and lower mirrors. Since the emission wavelength in the active layer is determined by the material and layer configuration of the active layer, it is necessary to design the Guided Resonance in the photonic crystal layer acting as the upper reflection mirror to correspond to the emission wavelength.

  As described above, the surface emitting laser can be realized by using the photonic crystal layer 1000 described in the first embodiment as an upper reflection mirror disposed to face the lower reflection mirror 5000 as shown in FIG.

Lower reflecting _{mirror, Al x Ga 1-x As} / Al x 'Ga 1-x' As, GaN / Al x Ga 1-x N, In x Ga 1-x As y P 1-y / In x 'Ga A multilayer mirror such as _{1-x ′} As _{y ′} P _{1-y ′} is used. Of course, a photonic crystal as shown in Embodiment 1 can also be applied.

(Active layer, clad layer, substrate, etc.)
The active layer 5900 has a multiple quantum well structure using a material such as GaInP / AlGaInP or GaN / InGaN, for example.

  The clad layer 1021 is, for example, AlGaInP, AlGaN, or the like.

  The substrate 5050 is, for example, GaAs or GaN.

  The VCSEL according to the present embodiment can be driven by an optical excitation method or a current injection method. In the figure, electrodes and the like are omitted.

  Note that a mirror configured to include a photonic crystal layer is referred to as a first reflection mirror, and a mirror disposed opposite to the first reflection mirror is sometimes referred to as a second reflection mirror. The first reflection mirror may be used as an upper reflection mirror as described above, or may be used as a lower reflection mirror.

(Embodiment 3: DFB type surface emitting laser)
A surface emitting laser related to a DFB type laser (Distributed Feed-Back Laser) according to the present embodiment will be described. FIG. 14 schematically shows a cross-sectional view of the configuration of the DFB laser.

  5050 is a substrate, 6000 is a cladding layer, 1010 is a first member, 1015 is a third member, 1000 is a photonic crystal layer (sometimes referred to as an optical resonance layer), 5900 is an active layer, and 5020 is an upper cladding layer. It is. Here, the cladding layer 6000 also serves as a low refractive index layer (second member) for the photonic crystal layer 1000.

  In the DFB type surface emitting laser, light generated in the active layer 5900 enters the photonic crystal layer 1000. The incident light becomes waveguide mode light, which is amplified by resonance in the in-plane direction of the photonic crystal layer 1000. And after that, it couple | bonds with a radiation mode and is radiated | emitted out of a photonic crystal layer. Thereby, coherent light is surface-emitted from the upper clad layer 5020.

  That is, the present embodiment is different in that the lower reflection mirror 5000 described in the second embodiment is not necessarily required.

  As the cladding layer 6000, the second member described in the first embodiment can be used. The materials described in Embodiment Mode 1 can be used for the substrate 5050, the active layer 5900, and the like.

  In the present embodiment, the active layer 5900 may be disposed at any position where light can be incident on the photonic crystal layer 1000 as an optical resonance layer. It is preferably provided at a position close to the nick crystal layer. For example, the active layer 5900 can be formed on the photonic crystal layer 1000. The active layer 5900 can also be disposed inside the photonic crystal layer 1000.

  In the above description, the clad layer 6000 is the low refractive index layer. However, the substrate 5050 may be a low refractive index layer. That is, the present invention includes a laser in which the photonic crystal layer 1000 is formed on the substrate 5050.

(Example 1: Mirror)
In Example 1, a two-dimensional photonic crystal mirror configured by applying the present invention will be described. FIG. 10D shows the configuration of the mirror in the present embodiment.

In FIG. 10D, reference numeral 1000 denotes a photonic crystal layer formed by providing cylindrical holes in a square lattice pattern in a layer made of GaN. The thickness of the layer is 100 nm, the interval between the cylindrical holes is 200 nm, the radius of the cylindrical holes is 60 nm, and the depth of the cylindrical holes is 40 nm (40% of the slab thickness). The cylindrical hole is filled with a thiourethane resin having a refractive index of 1.7, and the upper part of the photonic crystal layer is also covered with a third member 1017 made of the same resin. Reference numeral 1020 denotes a substrate made of Al _0.4 Ga _0.6 N.

FIG. 11 (d) shows the transmission spectrum calculation result of the configuration of FIG. 10 (d). The refractive index of GaN was 2.54, and the refractive index of Al _0.4 Ga _0.6 N was 2.32. The relative refractive index difference between the two is about 8.7%. For the sake of calculation, the thickness of the member 1017 and the substrate 1020 is assumed to be infinite.

  In FIG. 11D, it is confirmed that there is a wavelength region in which the transmittance sharply drops (that is, the reflectance increases rapidly) in the vicinity of the wavelength of 465 nm. Therefore, this configuration can be operated as a high reflectivity mirror.

  In addition, for comparison with the present example, the results of calculating the transmission spectrum for the configurations of FIGS. 10 (a), (b), and (c) in FIGS. 11 (a), (b), and (c), respectively. Indicates. 10A shows a configuration in which holes are provided to a depth of 100 nm (100% of the slab thickness), FIG. 10B shows a configuration in which a resin having a refractive index of 1.7 is filled in FIG. (C) is the structure which provided the cylindrical hole to the depth of 40 nm (40% of slab thickness). In FIGS. 11A, 11B, and 11C, there is no wavelength region with a high reflectance such that the transmittance is 10% or less (that is, the reflectance is 90% or more).

  In other words, in this configuration, it is not sufficient to perform the method of reducing the depth of the cylindrical hole and the method of filling the cylindrical hole with resin alone, and it will operate as a mirror only when two methods are employed. Can be made.

(Example 2: VCSEL)
In Example 2, a surface emitting laser (VCSEL) configured by applying the present invention will be described. FIG. 12 shows the configuration of the surface emitting laser in this example.

In FIG. 12, reference numeral 1000 denotes a photonic crystal layer formed by providing cylindrical holes in a square lattice pattern in a layer made of Al _0.5 Ga _0.5 As. The layer thickness is 308 nm, the spacing between the cylindrical holes is 205 nm, the radius of the cylindrical holes is 82 nm, and the depth of the cylindrical holes is 154 nm (50% of the slab thickness). The cylindrical hole is filled with an acrylic resin 1015 having a refractive index of 1.7, and a member 1017 made of the same material fills the upper portion of the photonic crystal layer 1000.

5020 is a p-type AlGaInP cladding layer, 5900 is a GaInP / AlGaInP multiple quantum well active layer, and 1021 is an n-type AlGaInP cladding layer. Further, 5000 is a lower mirror layer made of n-type Al _0.93 Ga _0.07 As / Al _0.5 Ga _0.5 As-DBR, and 5050 is a GaAs substrate. 1200 is a ring-type upper electrode, and 1210 is a lower electrode.

  FIG. 13 shows the transmission spectrum calculation result of the photonic crystal layer in FIG. It is confirmed that the mirror operates as a mirror having a high reflectance near the wavelength of 669 nm.

  Similarly, the lower mirror layer 5000 is designed to have a high reflectance around a wavelength of 669 nm. The resonator length determined by the distance between the photonic crystal layer 1000 and the lower mirror layer 5000 is designed such that the antinodes of standing waves formed in the resonator overlap the active layer 5900. For these, a method generally used in designing a surface emitting laser can be applied as it is.

  With the above configuration, laser oscillation is realized by resonating and amplifying the light generated in the active layer 5900 with the upper and lower mirrors.

It is a perspective view for demonstrating the photonic crystal layer based on this invention. It is sectional drawing for demonstrating the photonic crystal layer based on this invention. It is a graph which shows the hole depth dependence of a transmission spectrum. It is a graph which shows the hole depth dependence of a transmission spectrum. 6 is a schematic diagram for explaining a VCSEL according to Embodiment 2. FIG. It is a graph which shows the hole diameter dependence of a transmission spectrum. It is a graph which shows the transmission spectrum of the photonic crystal mirror of this invention. This is a photonic crystal described in Non-Patent Document 1. It is the transmission spectrum of nonpatent literature 1. 1 is a schematic diagram illustrating a photonic crystal mirror described in Example 1. FIG. 2 is a graph showing a transmission spectrum of a photonic crystal mirror described in Example 1. FIG. 6 is a schematic diagram illustrating a surface emitting laser described in Example 2. FIG. 6 is a graph showing a transmission spectrum of a photonic crystal mirror constituting the surface emitting laser described in Example 2. FIG. 6 is a schematic diagram for explaining a DFB type laser according to a third embodiment.

Explanation of symbols

1000 photonic crystal layer 1010 first member 1015 third member 1016 hole 1017 third member 1020 second member 5000 lower reflection mirror 5020 upper cladding layer 5050 substrate 5900 active layer 6000 cladding layer 8000 sapphire substrate 8030 nucleation layer 8050 Photonic crystal layer

Claims (9)

A structure having a photonic crystal layer,
A photonic crystal layer in which a plurality of holes are periodically arranged in a first member having a _first refractive index (n ₁ );
A second member having a _second refractive index (n ₂ ) lower than the first refractive index and adjacent to the photonic crystal layer;
A third member having a _third refractive index (n ₃ ) greater than 1.0 and lower than the first refractive index and formed on the first member;
The relative refractive index difference (= (n ₁ −n ₂ ) / n ₁ ) between the first refractive index and the second refractive index is 0.10 or less, and
The depth of the hole provided in the photonic crystal layer is 20% or more and 80% or less of the thickness of the first member.   The structure according to claim 1, wherein the third member is filled in the hole formed in the photonic crystal layer.   The structure according to claim 1, wherein the third member is formed on the photonic crystal layer.   The structure according to claim 1, wherein light guided in an in-plane direction of the photonic crystal layer is extracted out of the photonic crystal layer. A surface emitting laser,
A first reflecting mirror comprising the structure according to claim 1;
A second reflecting mirror disposed opposite to the first reflecting mirror;
A surface emitting laser comprising: an active layer disposed between the first reflecting mirror and the second reflecting mirror.   The surface emitting laser according to claim 5, wherein the second reflecting mirror includes the structure according to claim 1. A surface emitting laser,
An optical resonance layer comprising the structure according to claim 1;
A surface emitting laser comprising: an active layer disposed at a position where light can be incident on the optical resonance layer.   8. The surface emitting laser according to claim 7, wherein the active layer is formed on the optical resonance layer.   The surface emitting laser according to claim 7, wherein the active layer is disposed inside the optical resonance layer.

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