JP5352787B2 - Two-dimensional photonic crystal thermal radiation source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat radiation light source, capable of providing light of a wavelength of a specific narrow band. <P>SOLUTION: Two-dimensional photonic crystals are formed on a slab 21 having a quantum well structure obtained by alternately laminating a first semiconductor layer 211 and a second semiconductor layer 212 having partially overlapped electron band gaps by periodically forming pores 22 therein. A photonic band gap related to TM polarization as it includes a transition energy between a plurality of sub-bands of the quantum well is formed by appropriately arranging the pores 22. A spot-like defect 23 having a defect level corresponding to the energy width and a form asymmetric to the direction vertical to the slab is disposed within the slab 21. When this light source is heated, light of a wavelength corresponding to the transition between sub-bands is generated, and this light is taken through the defect 23 in the direction vertical to the slab 21. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a light source that emits light by heat radiation, and more particularly to a heat radiation light source that emits light of a specific narrow band of wavelengths with high efficiency.

  In addition to being able to emit light by Joule heat generated by supplying power to the heat radiator, the heat radiation light source can obtain light emission by applying heat to the heat radiator without depending on the power. Wide application range. For example, in an exhaust gas sensor used to analyze components in engine exhaust gas using infrared rays, infrared rays are generated from the heat radiator without using a separate power source or heat source by heating the heat radiator with engine waste heat. Expected to be used as an infrared source.

  The light emitted by the heat radiator has a spectrum over a wide wavelength range. For example, when the heat radiator is heated to several tens of degrees Celsius to several hundreds of degrees Celsius, the emission wavelength range is several μm to several tens of μm. However, since infrared sensors including the above-described exhaust gas sensor generally use only light of a predetermined wavelength, if such a heat radiation light source is used, light emission other than the predetermined wavelength is wasted and the light use efficiency is low. In addition, light having a wavelength other than the predetermined wavelength may adversely affect the measurement.

  Patent Document 1 describes that an infrared reflecting means for reflecting infrared light having a wavelength longer than the cutoff wavelength is provided on the surface of the heat radiator in order to increase the utilization efficiency as a visible light source for illumination. ing. According to this configuration, infrared light that cannot be used for illumination or the like can be prevented from being radiated to the outside, and the light utilization efficiency can be increased. However, in this configuration, all light having a wavelength shorter than the cut-off wavelength is radiated from the heat radiator. Therefore, when only a predetermined wavelength is desired as described above, there remains a problem in terms of light utilization efficiency.

JP 09-139193 A ([0008] to [0011], FIG. 1)

  The problem to be solved by the present invention is to provide a thermal radiation light source capable of efficiently obtaining light in a narrow wavelength band around a predetermined wavelength.

The thermal radiation light source according to the present invention made to solve the above problems is
A slab having a quantum well structure formed by stacking a plurality of types of semiconductors ;
A heat source for heating the slab ,
In the slab,
a) Refraction different from the plurality of types of semiconductors, which are periodically arranged in a large number so as to form a photonic band gap with respect to TM polarization, including transition energy between a plurality of subbands of the quantum well. A refractive index region having a refractive index;
b) A two-dimensional photonic crystal thermal radiation characterized by comprising a point-like defect consisting of point-like defects having a periodic arrangement in the different refractive index region and having a wavelength corresponding to the transition energy. Light source.
Moreover, the thing of the other aspect of the thermal radiation light source which concerns on this invention is
A slab having a quantum well structure formed by laminating a plurality of types of semiconductors,
In the slab,
a) Refraction different from the plurality of types of semiconductors, which are periodically arranged in a large number so as to form a photonic band gap with respect to TM polarization, including transition energy between a plurality of subbands of the quantum well. A refractive index region having a refractive index;
b) consisting of point-like defects with periodic arrangement of the different refractive index regions, and point-like defects in which light having a wavelength corresponding to the transition energy can exist inside
With
When the slab is heated and energy corresponding to the transition energy is supplied to the slab, light emission having a wavelength corresponding to the transition energy is generated.

Hereinafter, the configuration of the two-dimensional photonic crystal thermal radiation light source will be described in detail.
(1) Quantum well structure The above quantum well structure will be described with reference to FIG. A first semiconductor 121 having a first band gap 131 relating to the energy of electrons, and a second semiconductor 122 having a second band gap 132 that is narrower than the first band gap 131 and overlaps a part of the first band gap 131. The alternately stacked slabs 11 are formed. As a result, in the region 14 near the lower end of the conduction band 15 above (high energy side) the second band gap 132 of the second semiconductor 122 and sandwiched between the first band gaps 131, the first band gap is obtained. Only discrete energy levels determined by the difference H _A between the upper end of 131 and the upper end of the second band gap 132 and the thickness H _B of the second semiconductor 122 can be taken. Similarly, discrete energy levels are also formed in the valence band 16 on the lower side (low energy side) of the second band gap 132 of the second semiconductor 122. Such energy levels are called subbands. Here, the case where two types of semiconductors (first semiconductor and second semiconductor) are stacked has been described as an example. However, the quantum well structure and the subband can be formed by stacking three or more types of semiconductors. .

  After supplying electrons or holes to sub-bands on the low energy side by some method, the slab is heated and energy corresponding to the energy difference between the sub-bands is supplied to the slab. Hole transition occurs, and light emission having a wavelength corresponding to this energy difference occurs. Electrons and holes can be supplied, for example, by doping impurities in any of the semiconductors when producing quantum wells. Alternatively, electrons or holes (intrinsic carriers) excited from the valence band to the conduction band by heating can be supplied to the subband.

  The light obtained by the intersubband transition becomes TM (Transverse Magnetic) polarized light that vibrates in a direction perpendicular to the slab and in a direction parallel to the slab. Such TM-polarized light travels in a direction parallel to the slab and is emitted almost only from the end face of the slab, so the luminous efficiency is low. Therefore, in the present invention, the following two-dimensional photonic crystal and point defects are used in order to emit light from a large area of the slab surface like a conventional radiator.

(2) Two-dimensional photonic crystal and point-like defects In the slab 11, a large number of regions (different refractive index regions) having different refractive indexes from the first semiconductor and the second semiconductor that are the materials of the slab are periodically formed. Deploy. As a result, a band structure relating to light energy is formed, and an energy range (wavelength range, frequency range) in which light cannot propagate through the slab is formed. Such an energy range is called a photonic band gap (PBG). This PBG corresponds to the band gap of electrons formed by the periodic arrangement of atoms in the crystal, so that the different refractive index regions are periodically arranged as described above. Is called a photonic crystal, and in particular, one in which a different refractive index region is arranged in a slab is called a two-dimensional photonic crystal.

PBG is formed only for TM polarized waves, formed only for TE polarized waves (polarized waves whose electric field vibrates in a direction parallel to the slab), and formed for both TE polarized waves and TM polarized waves. There is a case. These depend on the shape and arrangement of the different refractive index regions. As described above, since light obtained by intersubband transition is TM polarization, a two-dimensional photonic crystal in which PBG is formed at least with respect to TM polarization is used in the present invention. Examples of two-dimensional photonic crystals on which such PBGs are formed include those in which equilateral triangular different refractive index regions described in JP-A-2004-294517 are arranged in a triangular lattice pattern, or JP-A-2005-099672 Examples are those in which different refractive index regions having C3v symmetry (symmetry having three-fold rotational symmetry and three mirror surfaces) described in the publication are arranged in a triangular lattice pattern.
The different refractive index region may be formed by embedding some member having a refractive index different from that of the slab, or may be formed by providing a hole in the slab. The latter is preferable because it is easier to manufacture and the difference in refractive index from the slab can be sufficiently increased.

  Point-like defects are provided in the periodic arrangement of the different refractive index regions in the slab 11. Due to the point defects, energy levels (defect levels) are formed in the PBG. As a result, light having a wavelength corresponding to the defect level may exist in a point defect (as opposed to the fact that PBG related to TM polarization is formed in a portion other than the defect). become able to. Since the defect level depends on parameters such as the shape and period of the different refractive index region (see, for example, JP-A-2001-272555), by adjusting these parameters, the defect level can be converted into the transition energy between subbands. The light emitted by the transition of electrons or holes between the subbands can be made to exist only in the point defect.

Such a point defect has the following two roles in the present invention.
The first role is to enhance the emission intensity at the resonance wavelength (wavelength corresponding to the defect level) by the resonance effect. In general, in heat radiation, as the product of the average length of light passing through the light emitter and the absorption coefficient increases, the light emission intensity approaches the light emission intensity of a black body, which is the theoretical limit. In the light source of the present invention, the light resonating with the spot-like defect stays in the spot-like defect for a longer time than the light of other wavelengths, so that the product of the passage length and the absorption coefficient is increased.
The absorption coefficient can be adjusted by the electron (hole) density of the quantum well structure, and the absorption coefficient increases as the electron (hole) density is increased. As described above, when the electron (hole) density is increased, the light of the resonance wavelength is saturated with the emission intensity approaching the intensity of blackbody radiation at a lower electron (hole) density than the light of other wavelengths. If the electron (hole) density is further increased, the intensity of light of other wavelengths also increases. Therefore, by setting the electron (hole) density of the quantum well structure to a minimum value at which the intensity of the resonant light (which is approximately equal to the intensity of the emitted light from the present radiation source) is saturated, It is possible to make the light emission intensity close to the theoretical limit and to keep light of other wavelengths sufficiently weak. The relationship between the electron (hole) density and the emission intensity at the resonance wavelength can be obtained by experiment or theoretical calculation.

  The second role is to emit light in the slab generated by intersubband transition in a direction perpendicular to the slab. That is, light having a wavelength corresponding to a defect level that can exist in a point-like defect cannot propagate in a direction parallel to the slab because the two-dimensional photonic crystal is formed, It is emitted from the point defect in the direction perpendicular to the slab. Thereby, the light generated by the intersubband transition can be emitted from the surface of the slab.

Further, it is desirable that the point defect has an asymmetric shape with respect to the direction perpendicular to the slab. Due to this asymmetry, an electric field component parallel to the slab (which is 0 for TM polarization) is generated in the light within the point-like defect, which makes it easier for the light to be emitted in a direction perpendicular to the slab. Examples of such a point defect include a conical shape described in the above-mentioned JP-A-2001-272555, and a slab having a step-like cross section perpendicular to the slab with different areas on the upper and lower surfaces of the slab. There is.
Even in such a point defect without asymmetry, a slight electric field component parallel to the slab is generated due to the influence of the interface between the slab and the outside (air), but the shape of the point defect is made asymmetric. The component can be enlarged by.

  In order to efficiently select the wavelength of light obtained by intersubband transition and emit light from a wide range of the surface of the slab like a radiator, it is desirable to provide a large number of point defects on one slab. However, if the number of point-like defects is too large, the periodicity of the arrangement of the different refractive index regions is impaired, and the formation of PBG becomes difficult. In addition, the point defects are coupled to each other, which causes the resonance wavelength to broaden, so that the wavelength selectivity is lowered. Therefore, it is desirable to arrange the point defects so as to be separated from each other by 6 cycles or more in the period of the different refractive index region.

  When the PBG of the two-dimensional photonic crystal is formed only with respect to the TM polarization, light having an electric field component in a direction parallel to the slab generated in the point-like defect leaks into the two-dimensional photonic crystal. Therefore, it is desirable that a PBG for both TM polarization and TE polarization is formed in the transition energy (energy difference) between the subbands. Such a PBG is called a complete PBG. The two-dimensional photonic crystal in which the above-mentioned equilateral triangular different refractive index regions are arranged in a triangular lattice shape, or a different refractive index region having C3v symmetry is formed in a triangular lattice shape. Formed in a two-dimensional photonic crystal or the like. With this complete PBG, light having an electric field component in a direction parallel to the slab generated in the point defect can no longer propagate through the two-dimensional photonic crystal, and light leakage can be prevented.

(3) Two-dimensional photonic crystal having a three-direction tilted different refractive index region Next, a preferred configuration of the two-dimensional photonic crystal thermal radiation light source of the present invention will be described. The two-dimensional photonic crystal thermal radiation light source has the above-described configuration.
The different refractive index regions are arranged in a triangular lattice shape on the first surface, which is one surface of the slab, and so as to have at least three-fold rotational symmetry with respect to each lattice point;
Further, the different refractive index region is rotated in at least three times with respect to each lattice point in the form of a triangular lattice in a position complementary to the triangular lattice on the first surface on the second surface which is the other surface of the slab. Arranged so as to have symmetry,
Columns of the different refractive index regions extend from the respective lattice points on the first surface toward the three lattice points on the second surface that are closest to the lattice point.
It is characterized by that.

Here, the fact that the triangular lattice on the second surface is in a position complementary to the triangular lattice on the first surface means that each lattice point of the triangular lattice on the second surface is from the lattice point of the triangular lattice on the first surface. It is arranged at the position of the center of gravity of the triangle.
In the present application, the different refractive index region formed in such a shape is referred to as a “three-direction inclined different refractive index region”. For the two-dimensional photonic crystal with a three-direction tilted different refractive index region, the third volume of the 2006 Spring 53rd Joint Conference on Applied Physics, Lecture No. 22a-L-11 (Author: Kitagawa) Etc.).

  A two-dimensional photonic crystal having a three-direction tilted different refractive index region is one type of the above-described two-dimensional photonic crystal having C3v symmetry, and can form a complete PBG. This two-dimensional photonic crystal has a feature that it has a larger complete PBG than a two-dimensional photonic crystal having a regular refractive index region. In addition, a point defect having an asymmetric shape with respect to the direction perpendicular to the slab can be formed by deleting a part of the different refractive index region, in other words, by not forming a part of the different refractive index region. This is a feature of a two-dimensional photonic crystal having a three-direction tilted different refractive index region.

  According to the two-dimensional photonic crystal thermal radiation light source according to the present invention, it is possible to obtain light having a strong intensity only at a predetermined wavelength, which cannot be obtained with a conventional thermal radiation light source. That is, only light of a predetermined wavelength can be selectively extracted with high efficiency. Further, like the conventional heat radiation light source, this light can be emitted from a wide range of the surface of the radiator.

  In addition, the two-dimensional photonic crystal thermal radiation light source of the present invention can obtain light having a strong intensity only at a predetermined wavelength simply by heating, so that an exhaust gas sensor for analyzing components in engine exhaust gas. As described above, the present invention is particularly effective for application to an infrared sensor used in an environment where a heat source exists.

An embodiment of a two-dimensional photonic crystal thermal radiation light source according to the present invention will be described with reference to FIGS. FIG. 2 is a perspective view of the thermal radiation light source of this embodiment. The thermal radiation light source of this embodiment includes a slab 21 in which first semiconductor layers 211 made of Al _x Ga _1-x As and second semiconductor layers 212 made of GaAs are alternately stacked. In this embodiment, x = 0.27, and the thicknesses of the first semiconductor layer 211 and the second semiconductor layer 212 are 15 nm and 7.5 nm, respectively. The upper end of the band gap of the first semiconductor layer 211 is the energy difference H _A of the upper end of the band gap of the second semiconductor layer 212 is 0.27 eV. The energy difference between the first subband with the lowest energy among the subbands and the second subband with the next lowest energy is 0.12 eV. GaAs is injected with electrons to contribute to intersubband transition by replacing part of Ga with Si. The electron concentration will be described later.

  In the slab 21, a three-direction inclined different refractive index region composed of holes 22 extending in a direction inclined with respect to the normal line of the slab 21 is periodically arranged. The configuration of the three-direction tilted different refractive index region used in the present embodiment is shown in FIG. FIG. 3A shows the shapes of the different refractive index regions on the upper surface (shown by a solid line) and the lower surface (shown by a broken line) of the slab 21. The cross sections of the holes 22 on the upper and lower surfaces of the slab are both circular and arranged in a triangular lattice shape. The cross section 221 of the hole on the upper surface is disposed immediately above the center of gravity of the triangular lattice by the cross section 222 of the hole on the lower surface, and similarly, the cross section 222 is disposed immediately below the center of gravity of the triangular lattice by the cross section 221. As shown in FIG. 3 (b), the three holes 22 extend in a direction inclined with respect to the slab 21 from the cross section 221 toward the three closest cross sections 222. Similarly, three holes 22 extend in a direction inclined with respect to the slab 21 from the cross section 222 toward the three closest cross sections 221 (FIG. 3 (c)). Since the holes 22 are formed in this way, the cross-sectional shape of the holes 22 has C3v symmetry in a cross section parallel to the slab 21 at an arbitrary position in the slab 21. Thereby, a complete PBG is formed in the wavelength band determined by the period of the holes 22. In the present embodiment, the period of the holes 22 is 4 μm. In this case, the complete PBG is formed between wavelengths of approximately 9.5 μm to 11.1 μm.

  A point-like defect 23 is formed in the slab 21 by deleting a part of the holes 22 (not providing a part of the holes 22). In the present embodiment, as shown in FIG. 4, three of the three lattice points 241 to 243 adjacent to each other on the straight line among the triangular lattices on the upper surface of the slab 21 are directed toward the lower surface of the slab 21. The voids 22 extending in the direction of were removed. In this case, lattice points 241 to 243 having no holes 22 are present on the upper surface of the slab 21. On the other hand, there is no such lattice point on the lower surface of the slab 21, and at any lattice point where the void 22 is missing, one or two voids 22 that are not missing extend from the lattice point. ing. Therefore, the point defect 23 of this embodiment has an asymmetric structure with respect to the direction perpendicular to the slab.

A large number of point-like defects 23 are provided in the slab 21 as shown in the top view of FIG. In the present embodiment, two rectangular unit regions 25 having a long side length of 12a (a is a period of a triangular lattice) and a short side length of 4 × 3 ^1/2 a (vertex of the unit region and The point-like defects 23 were arranged at a ratio of 1 each to the face center. The number of lattice points for the point defect 23 in the unit region 25 is such that the periodicity of the two-dimensional photonic crystal is not impaired and the coupling between the point defects is sufficiently small. The number was sufficiently small, 1/16 of the total number of lattice points.

In the two-dimensional photonic crystal thermal radiation light source of this embodiment, when the slab 21 is heated, electron transition occurs between a number of subbands formed by the first semiconductor layer 211 and the second semiconductor layer 212. This electron transition generates TM polarized light having a frequency (wavelength) corresponding to the energy difference between the subbands.
Here, in the above-described quantum well, since electrons can move freely in a direction parallel to the slab, in addition to light emission due to intersubband transition, light emission occurs over a wide wavelength band by free electrons. . By making the resonance frequency of the point defect 23 coincide with the light emission frequency due to the transition between the subbands, the light generated by the transition between the subbands is longer for a longer time than the light having a frequency other than the resonance frequency. Therefore, the interaction between light and electrons is strengthened and light emission is selectively enhanced, and the intensity approaches the level of black body radiation. On the other hand, since light having a frequency other than the resonance frequency of the point defect 23 interacts with electrons only for a time that passes through the thin slab, light emitted in the vertical direction is compared with light having the resonance frequency of the point defect 23. And stay at a weak level.
The light of the selected frequency is emitted in a direction perpendicular to the slab 21 from the point defect 23 because an electric field component parallel to the slab 21 which is not in the TM polarized light is generated due to the asymmetry of the point defect 23. . In addition, since a large number of point-like defects 23 are arranged, light emission can be obtained from a wide range where the point-like defects 23 are arranged.

The result obtained by calculating the emission spectrum in the two-dimensional photonic crystal thermal radiation light source of the above embodiment using a three-dimensional FDTD (Finite Difference Time Domain) method will be described with reference to FIG. Here, the calculation was performed for the case where the concentration of electrons injected into the second semiconductor layer 212 was 1 × 10 ¹⁸ cm ⁻³ and the light source was heated to 600K. For the sake of calculation, only one point defect 23 is assumed. As a comparative example, when a slab (electron density: 1 × 10 ¹⁸ cm ⁻³ ) having the same quantum well structure as the slab 21 in the above embodiment and having no holes 22 is heated to 600 K (Comparative Example 1, FIG. 7 (a)), and a case where a slab made of only GaAs having a quantum well structure and no holes 22 and having a thickness and an electron density equal to those of the slab 21 is heated to 600 K (Comparative Example 2, FIG. 7B). Similar calculations were performed. 6 and 7, the intensity of light emitted in the direction perpendicular to the slab (from the surface of the slab) is represented by a solid line, and the intensity of light emitted in the direction parallel to the slab (from the end of the slab). The intensity is represented by a broken line. The horizontal axis of the graph is a normalized frequency in which the frequency of light is normalized by c / a (c is the speed of light, and a is the period of the holes 22 in the present embodiment). The unit of light intensity shown on the vertical axis is an arbitrary unit, but it is possible to compare intensities between the three graphs of FIG. 6, FIG. 7 (a) and FIG. 7 (b).

  In Comparative Example 2, the light intensity is distributed over a wide frequency range in accordance with Planck's law regarding black body radiation. In Comparative Example 1, a strong peak is observed at the normalized frequency of 0.3825. The reason why only light of a specific frequency is emitted with a strong intensity is considered to be due to a transition between subbands having a magnitude corresponding to this frequency. However, most of the light of that frequency is emitted from the end of the slab and not much from the surface of the slab. This is considered to be due to the fact that the light generated by the transition between subbands is TM polarization.

  On the other hand, in the present embodiment, light having a normalized frequency of 0.3825 generated by intersubband transition is hardly emitted from the end of the slab. This is because light of this frequency cannot propagate in a direction parallel to the slab because this frequency is within the range of the PBG formed in this embodiment. On the other hand, light of this frequency is emitted with high intensity from the surface of the slab. The reason why such a strong intensity is obtained is that (i) light emission at this frequency is selectively enhanced by the point defect 23, and (ii) the polarization direction is caused by the asymmetry of the shape of the point defect 23. Since TM is converted into a direction that includes an electric field component parallel to the slab, light can be extracted in the direction perpendicular to the slab, and (iii) a complete PBG is formed in the two-dimensional photonic crystal at this frequency. Therefore, it is considered that light leaking into the slab caused by the electric field oscillating in the direction parallel to the slab, which is generated when the polarization direction is changed, is suppressed.

In the two-dimensional photonic crystal thermal radiation light source of the above embodiment, emission spectra were calculated for a plurality of examples having different concentrations of electrons injected into the second semiconductor layer 212. The calculation conditions are the same as in Example 1 except for the electron concentration. The electron concentration is 1 × 10 ¹⁵ cm ⁻³ , 1 × 10 ¹⁶ cm ⁻³ , 5 × 10 ¹⁶ cm ⁻³ , 1 × 10 ¹⁷ cm ⁻³ , 2 × 10 ¹⁷ cm ⁻³ , 5 × 10 ¹⁷ cm ⁻³ , (1 × 10 ¹⁸ cm ⁻³ : First Example), 1 × 10 ¹⁹ cm ⁻³ .

  The calculation results are shown in FIG. In any case, with respect to light having a normalized frequency of 0.3825, the intensity of light emitted from the surface of the slab is maximized, and light emitted from the end of the slab is suppressed by PBG. Further, as the electron concentration in the second semiconductor layer 212 increases, light emission from the frequency region outside the PBG other than the light having the normalized frequency of 0.3825 increases.

FIG. 9 shows changes in emission intensity depending on the electron density of the second semiconductor layer 212 for light having a normalized frequency of 0.15 (outside the PBG) and light having a 0.3825. In the range where the electron density is 2 × 10 ¹⁷ cm ^-3 or less, the light with the normalized frequency of 0.15 and the light with 0.3825 both increase in intensity as the electron density increases, and the light with the normalized frequency of 0.3825 is 0.15. The intensity is two orders of magnitude greater than light. On the other hand, in the range where the electron density is 2 × 10 ¹⁷ cm ⁻³ or more, the light with the normalized frequency of 0.15 increases in intensity as the electron density increases as in the case where the electron density is 2 × 10 ¹⁷ cm ⁻³ or less. In contrast, the intensity of the light with the normalized frequency of 0.3825 is saturated. Such saturation occurs because the transition between subbands is concentrated at one frequency (0.3825), and light at that frequency is enhanced by point defects, so it is lower than light at other frequencies. This is probably because the electron density approaches the intensity of blackbody radiation. Therefore, in order to obtain strong light emission at the resonance frequency of the point-like defect (frequency related to the transition between subbands) and suppress light emission at other wavelengths, the electron density is a range in which the light emission intensity of the transition between subbands is saturated It is desirable to set the smallest value within 31 (2 × 10 ¹⁷ cm ^{−3 in} this embodiment).

The conceptual diagram for demonstrating the quantum well structure used in this invention. The perspective view which shows one Embodiment of the two-dimensional photonic crystal thermal radiation light source which concerns on this invention. The top view and perspective view which show the structure of the 3 direction inclination different refractive index area | region in this embodiment. The top view which shows the structure of the point defect 23 in this embodiment. The top view which shows arrangement | positioning of the point-like defect 23 in the upper surface of the slab 21. FIG. The graph which shows the calculation result of the emission spectrum of the two-dimensional photonic crystal thermal radiation light source of 1st Example. The graph which shows the calculation result of the spectrum of the radiation produced when the slab of a comparative example is heated. The graph which shows the calculation result of the emission spectrum of the two-dimensional photonic crystal thermal radiation light source of 2nd Example. 7 is a graph showing the relationship between the electron density and the light emission intensity of the second semiconductor layer 212.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11, 21 ... Slab 121 ... 1st semiconductor 122 ... 2nd semiconductor 131 ... 1st band gap 132 ... 2nd band gap 14 ... Area | region 15 in which a subband is formed ... Conductive band 211 ... 1st semiconductor layer 212 ... 2nd Semiconductor layer 22 ... hole 221 ... cross section 222 of hole 22 on the upper surface of the slab ... cross section 23 of hole 22 on the lower surface of the slab ... dot-like defects 241, 242, 243 ... lattice points

Claims (6)

A slab having a quantum well structure formed by stacking a plurality of types of semiconductors ;
A heat source for heating the slab ,
In the slab,
a) Refraction different from the plurality of types of semiconductors, which are periodically arranged in a large number so as to form a photonic band gap with respect to TM polarization, including transition energy between a plurality of subbands of the quantum well. A refractive index region having a refractive index;
b) A two-dimensional photonic crystal thermal radiation characterized by comprising a point-like defect consisting of point-like defects having a periodic arrangement in the different refractive index region and having a wavelength corresponding to the transition energy. light source. A slab having a quantum well structure formed by laminating a plurality of types of semiconductors,
In the slab,
a) Refraction different from the plurality of types of semiconductors, which are periodically arranged in a large number so as to form a photonic band gap with respect to TM polarization, including transition energy between a plurality of subbands of the quantum well. A refractive index region having a refractive index;
b) consisting of point-like defects with periodic arrangement of the different refractive index regions, and having point-like defects in which light having a wavelength corresponding to the transition energy can exist inside,
A two-dimensional photonic crystal thermal radiation light source characterized in that when the slab is heated and energy corresponding to the transition energy is supplied to the slab, light emission having a wavelength corresponding to the transition energy is generated . 2-dimensional photonic crystal heat radiation source according to claim 1 or 2, wherein the point defect is characterized by having an asymmetrical shape with respect to a direction perpendicular to the slab. The two-dimensional photonic crystal according to any one of claims 1 to 3, wherein the different refractive index regions are arranged so as to form a complete photonic band gap including the transition energy. Thermal radiation light source. The different refractive index regions are arranged in a triangular lattice shape on the first surface, which is one surface of the slab, and so as to have at least three-fold rotational symmetry with respect to each lattice point;
In the second surface, which is the other surface of the slab, the different refractive index region is in a triangular lattice shape that is complementary to the triangular lattice of the first surface, and at least three-fold rotational symmetry with respect to each lattice point Are arranged to have
Columns of the different refractive index regions extend from the respective lattice points on the first surface toward the three lattice points on the second surface that are closest to the lattice point.
The two-dimensional photonic crystal thermal radiation light source according to claim 4 . 2-dimensional photonic according to any one of claims 1 to 5, characterized in that a minimum intensity of the emitted light is saturated from the electrons or holes density, the thermal radiation source of the quantum well structure Crystal heat radiation light source.

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