JP4479214B2 - Semiconductor laser - Google Patents

Description

  The present invention relates to a semiconductor laser, and more particularly to a broad area type semiconductor laser.

  Semiconductor lasers are applied to various fields such as displays, printing equipment, material processing, and medical care, in addition to use as light sources in optical disk devices such as CDs (compact disks) and DVDs (digital video disks). In these applications, high output is often required, and recently, high-power semiconductor lasers have been actively developed.

  As one method for increasing the output of a semiconductor laser, it is effective to widen the stripe width of a semiconductor laser having a striped light emitting region. For example, the typical value of the stripe width in a semiconductor laser for optical disks is 2 to 3 μm, whereas in a high-power semiconductor laser, a so-called broad area type semiconductor laser in which the stripe width is increased to 50 μm or 100 μm also appears. ing. In a semiconductor laser generally called a broad area type, the width of the light emission stripe is at least 5 μm or more, most of which is set to 10 μm or more (the maximum width is about several hundreds of μm). As a technique related to the broad area type semiconductor laser, one described in Patent Document 1 below is known.

Japanese Patent Laid-Open No. 2003-60288

  However, in the case of a broad area type semiconductor laser, there is a problem that the NFP (Near Field Pattern) indicating the light intensity distribution in the light emitting region becomes non-uniform. Since this problem causes unevenness in emission intensity in the stripe width direction, it becomes a major obstacle to application to displays and printing equipment. In addition, one of the causes of the above problem is a phenomenon in which light is generated from a specific portion more intensely than other portions (hereinafter referred to as “filamentation”) because the stripe-shaped light emitting region is wide. It has been pointed out. Therefore, in order to make the NFP more uniform, it is necessary to suppress the occurrence of filamentation. In addition, when the active region becomes wider by increasing the stripe width, a plurality of longitudinal modes stand in the active region. However, since these longitudinal modes rarely affect each other, the width of the emission spectrum is consequently reduced. It becomes wide.

  The present invention has been made to solve the above-described problems, and an object thereof is to make NFP uniform in a broad area type semiconductor laser.

The semiconductor laser according to the present invention forms an optical waveguide using an active layer and two cladding layers, and at least one of the laser end faces provided at both ends in the axial direction of the waveguide. A diffractive part that diffracts light guided in the waveguide in a direction different from the axial direction of the waveguide in a plane parallel to the active layer is provided in the vicinity, and the diffractive part is made of a two-dimensional photonic crystal. In the photonic crystal, a linear defect is provided .

In the semiconductor laser according to the present invention, light is diffracted by a diffractive portion made of a two-dimensional photonic crystal having a linear defect portion in the crystal provided in the vicinity of the laser end face, thereby guiding it in the vicinity of the laser end face. Light is dispersed in a direction perpendicular to the axial direction of the waveguide. Therefore, the light intensity is made uniform in a direction perpendicular to the axial direction of the waveguide.

According to the semiconductor laser of the present invention, a diffractive part is provided in the vicinity of the laser end face, and the diffractive part is made of a two-dimensional photonic crystal in which a linear defect is provided in the crystal. For this reason, by diffracting the light guided in the waveguide by the diffraction section, the intensity of the light is made uniform in the direction orthogonal to the axial direction of the waveguide, and a good NFP can be obtained.

  Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.

  1A and 1B show a configuration example of a semiconductor laser according to an embodiment of the present invention, in which FIG. 1A is a plan view and FIG. 1B is a cross-sectional view thereof. The semiconductor laser shown in the figure is a broad area type semiconductor laser, which is an n-type substrate (semiconductor substrate) 1 serving as a base, an n-type cladding layer 2 sequentially stacked on the substrate 1, and an n-type substrate. The guide layer 3 includes an active layer 4, a p-type guide layer 5, a p-type cladding layer 6, and a p-type cap layer (contact layer) 7.

The substrate 1 is made of, for example, an n-type GaAs substrate. The n-type cladding layer 2 is made of, for example, an n-type Al _0.35 Ga _0.65 As layer. This clad layer 2 is formed on an n-type substrate 1. The n-type guide layer 3 is made of, for example, an n-type Al _0.30 Ga _0.70 As layer. The guide layer 3 is formed on the n-type cladding layer 2. The active layer 4 has a quantum well structure made of, for example, an Al _0.03 Ga _0.97 As layer. The active layer 4 is formed on the n-type guide layer 3.

The p-type guide layer 5 is made of, for example, an Al _0.30 Ga _0.70 As layer. The guide layer 5 is formed on the active layer 4. The p-type cladding layer 6 is made of, for example, an Al _0.35 Ga _0.65 As layer. The clad layer 6 is formed on the p-type guide layer 5. The p-type cap layer 7 is made of, for example, a GaAs layer. The cap layer 7 is formed in a stripe shape on the p-type cladding layer 6. A current confinement layer 8 is formed on both sides of the cap layer 7. The current confinement layer 8 limits the p-side current path to a predetermined stripe width, and is constituted by an insulating layer such as silicon nitride or silicon oxide, or a high resistance layer obtained by implantation of impurity ions. Although not shown, a p-side electrode is formed on the cap layer 7 using an electrode material such as Ti, Pt, or Au, and a reverse side of the substrate 1 on the opposite side is formed on, for example, Ge. An n-type electrode is formed using an electrode material such as Au.

  In the semiconductor laser having the above configuration, an optical waveguide is formed by the n-type cladding layer 2, the n-type guide layer 3, the active layer 4, the p-type guide layer 5, and the p-type cladding layer 6. At the same time, the laser end faces 9A and 9B at both ends in the X direction, which is the axial direction of the waveguide, serve as reflecting mirror surfaces to form a resonator. The light reflectance at one laser end face 9A is lower than the light reflectance at the other laser end face 9B. For example, the reflectance of the laser end surface 9A is approximately 10%, and the reflectance of the laser end surface 9B is approximately 100%. As a result, when the semiconductor laser is driven, the light traveling (reciprocating) in the X direction in the waveguide is emitted in the direction of the arrow from the laser end surface 9A on the low reflection side in a state of oscillating at a predetermined frequency. Become. Note that the X direction shown in FIG. 1 is a direction that coincides not only with the axial direction of the waveguide described above, but also with the resonator axis direction and the stripe axis direction of the semiconductor laser.

  In addition, a diffractive portion 10 is provided in the vicinity of the laser end surface 9B opposite to the laser beam emission side. The diffractive portion 10 diffracts light traveling in the X direction in the waveguide in a direction different from the X direction (axial direction of the waveguide), and is formed over the entire width of the semiconductor laser in the vicinity of the laser end face 9B in the X direction. Has been. In the thickness direction of the semiconductor laser, the diffractive portion 10 is formed so as to substantially penetrate the p-type cap layer 7, the p-type cladding layer 6 and the p-type cladding layer 5. Further, in the length direction of the semiconductor laser, the diffractive portion 10 is formed in a dimension range of about 1/5 to 1/10 of the total length of the laser from the laser end face 9B.

  The diffraction unit 10 is configured by a two-dimensional photonic crystal. A photonic crystal is a structure having a periodic refractive index distribution by arranging two types of media having different refractive indexes at a period that is the same as or slightly smaller than the wavelength of light. The two-dimensional photonic crystal is a photonic crystal in which a refractive index distribution is provided in a two-dimensional direction (planar shape).

  2A and 2B show an example of the structure of the diffractive portion 10 made of a photonic crystal. 2A is a perspective view of the diffractive portion 10 made of a photonic crystal, and FIG. 2B is an enlarged plan view thereof. As shown in the drawing, in the diffractive portion 10, small circular holes 11 (having a constant hole diameter) 11 are two-dimensionally arranged at a constant period in a plane parallel to the active layer 4. That is, in the orthogonal biaxial direction that forms approximately 45 degrees with the axial direction X of the waveguide, since the crystal structure is a square lattice, the arrangement pitches (center pitches) P1, P2 of the holes 11 adjacent to each other. Are set equal to each other. Each hole 11 forms a lattice point of the photonic crystal, and in the illustrated case, it is a two-dimensional photonic crystal having a square hole of a square lattice.

  Each side of the smallest square formed by connecting the lattice points has an inclination of approximately 45 degrees with respect to the X direction that is the axial direction of the waveguide. Further, when the refractive index of the hole 11 is na and the refractive index of the portion other than the hole 11 is nb, the relationship thereof is na ≠ nb (na> nb or na <nb).

  Next, a semiconductor laser manufacturing method according to an embodiment of the present invention will be described with reference to FIG.

  First, as shown in FIGS. 3A and 3B, a wafer-like substrate 1 serving as a base of a semiconductor laser is prepared, and n on the substrate 1 is formed by, for example, MOCVD (metal organic chemical vapor deposition). A type cladding layer 2, an n-type guide layer 3, an active layer 4, a p-type guide layer 5, a p-type cladding layer 6 and a p-type cap layer 7 are sequentially stacked.

  Next, as shown in FIG. 3C, an etching mask 12 is formed on the surface of the substrate 1 on which the cap layer 7 is formed. The etching mask 12 is formed in a predetermined pattern by photolithography (resist application, pre-baking, exposure by electron beam drawing, development, washing, etc.). This mask pattern is a pattern in which a portion corresponding to the hole 11 (see FIG. 2) is opened in a circle in the formation region of the diffractive portion 10 made of a photonic crystal.

  Subsequently, as shown in FIG. 3D, the semiconductor layer (cap layer 7, p-type layer) on the substrate 1 is formed by a dry etching method such as RIE (reactive ion etching) or high frequency inductively coupled plasma (ICP) etching. As shown in FIG. 3E, the cladding layer 6 and the p-type guide layer 5) are dug (cut) from the surface side, so that the cap layer 7, the p-type cladding layer 6 and the p-type guide layer are formed. 5 is formed with a large number of holes 11 penetrating substantially. The etching mask 12 is removed after the etching is completed.

  In etching, it is desirable to appropriately set (select) the etching conditions so that the bottom of the hole 11 does not reach the active layer 4 (in other words, the active layer 4 is not damaged by the etching). However, if the depth of the hole 11 is too shallow, the difference in refractive index that the light feels due to the presence of the photonic crystal when light is confined and guided in the active layer 4 becomes small. Therefore, it is desirable to control the etching amount (depth of the hole 11) so that the bottom of the hole 11 reaches at least the p-type guide layer 4.

  Therefore, as shown in FIG. 4, a semiconductor laser has a ΔT gap between the bottom of the diffractive portion 10 (hole 11) made of photonic crystal and the active layer 4, and this gap portion. May be embedded in the p-type guide layer 5. After completion of the etching, electrodes are formed by vapor deposition of metal on the front surface side (p side) and the back surface side (n side) of the substrate 1 by an electrode formation process.

  In a semiconductor laser obtained by such a manufacturing method, when metal is deposited by an electrode formation process, each hole 11 provided in a photonic crystal formation region (hereinafter also referred to as a photonic crystal region) is provided. It has a structure that contains metal. Therefore, in the photonic crystal formation region, a metal material having a refractive index different from that of the semiconductor material constituting the p-type guide layer 5 adjacent to the active layer 4 is periodically and regularly arranged.

Here, the periodic structure of the photonic crystal functions optically effectively when the wavelength of the light guided in the waveguide is equal to or less than the wavelength of the light. When it is about 800 nm, the effective refractive index (refractive index that the guided light feels on average) is n _eff = 4, and the value obtained by dividing the light wavelength by this value is 200 nm (= 800 ÷ 4). It is desirable to set a value less than or equal to the period of the refractive index distribution. For example, in the photonic crystal structure shown in FIG. 2, the intervals P1 and P2 of the holes 11 that are the period of the refractive index distribution are both set to 200 nm, and the respective hole diameters (diameters) are 1 / 2 is preferably set to 100 nm.

As another material system, for example, when the wavelength of light is about 650 nm with a GaInP / AlGaInP-based material, the effective refractive index is n _eff = 4, and the value obtained by dividing the light wavelength by this value is 160 nm. It is desirable to set a value of (≈650 ÷ 4) or less as the period of the refractive index distribution. When the light wavelength is about 405 nm in a GaInN / AlGaInN-based material, the effective refractive index is n _eff = 2.5, and the value obtained by dividing the light wavelength by this value is 160 nm (≈405 ÷ 2. It is desirable to set a value of 5) or less as the period of the refractive index distribution. Further, when the wavelength of light is about 1300 nm (1.3 μm) with a GaInNAs / GaAsN-based material, the effective refractive index is n _eff = 3.5, and the value obtained by dividing the light wavelength by this value is 370 nm ( It is desirable to set a value of approximately 1300 ÷ 3.5) or less as the period of the refractive index distribution.

  Incidentally, here, an example in which the n-type guide layer 3 is formed in the lower layer of the active layer 4 and the p-type guide layer 5 is formed in the upper layer is illustrated, but the present invention does not have any one of the guide layers. It can also be applied to those without both guide layers. For example, as shown in FIG. 5, in the case of employing a three-layer slab waveguide in which the active layer 4 is sandwiched between an n-type cladding layer 2 and a p-type cladding layer 6 (without a guide layer), the laser beam A diffractive portion 10 made of a photonic crystal is provided in the vicinity of the laser end surface opposite to the emission side, and the bottom of the diffractive portion 10 is a semiconductor layer adjacent to the upper surface of the active layer 4, that is, a p-type cladding layer. It is arranged to reach 6.

  Further, the semiconductor laser manufacturing method may be based on the flow shown in FIGS. The manufacturing method will be described. First, as shown in FIGS. 6A and 6B, a wafer-like substrate 1 serving as a base of a semiconductor laser is prepared, and an n-type is formed on the substrate 1 by, for example, MOCVD. The clad layer 2, the n-type guide layer 3, the active layer 4, the p-type guide layer 5, and the p-type clad layer 6 are sequentially laminated. At this time, when part or all of the p-type cladding layer 6 is crystal-grown, the substrate 1 is once taken out of the crystal growth apparatus.

  Next, as shown in FIG. 6C, an etching mask 12 is formed on the surface of the substrate 1 on which the p-type cladding layer 6 is formed. The etching mask 12 is formed in a predetermined pattern by photolithography (resist application, pre-baking, exposure by electron beam drawing, development, washing, etc.). This mask pattern is a pattern in which a portion corresponding to the hole 11 (see FIG. 2) is opened in a circle in the formation region of the diffractive portion 10 made of a photonic crystal.

  Subsequently, as shown in FIG. 6D, the semiconductor layer (p-type cladding layer 6) on the substrate 1 is formed by a dry etching method such as RIE (reactive ion etching) or high frequency inductively coupled plasma (ICP) etching. By digging (scraping) the p-type guide layer 5) from the surface side, as shown in FIG. 6E, a large number of holes almost penetrating the p-type cladding layer 6 and the p-type guide layer 5 are obtained. Part 11 is formed. The etching mask 12 is removed after the etching is completed. It is desirable to appropriately set the etching conditions so that the bottom of the hole 11 reaches the p-type guide layer 5 and does not reach the active layer 4 during this etching.

  Next, as shown in FIG. 6 (F), the substrate 1 is reintroduced into the crystal growth apparatus, and the remaining p-type cladding layer 6 or the p-type cap layer 7 is formed by a method similar to the above (for example, MOCVD method). Then, electrodes are formed by vapor deposition of metal on the front surface side (p side) and the back surface side (n side) of the substrate 1 by an electrode formation process. This manufacturing method has a structure in which the material for forming the p-type cladding layer 6 or the cap layer 7 enters each hole 11 provided in the formation region of the photonic crystal. Therefore, in the photonic crystal formation region, a p-type cladding layer material or a p-type cap layer material having a refractive index different from that of the semiconductor material constituting the p-type guide layer 5 adjacent to the active layer 4. Becomes a structure that is regularly arranged regularly. Further, depending on the conditions of the second crystal growth, it is conceivable that the semiconductor material does not enter the hole 11 due to the influence of the surface tension and the like, and the crystal growth proceeds while the hole 11 remains void. The material of the guide layer 5 has a structure in which voids having different refractive indexes are periodically arranged regularly.

  In operating the semiconductor laser having the above configuration, when a forward current is passed from the stripe-shaped current injection region, a stripe-shaped inversion distribution region is formed in the active layer 4 and is accompanied by the formation of the inversion distribution region. Light is generated inside the active layer 4 by stimulated emission. The light thus generated travels in the X direction along the waveguide, is amplified while being repeatedly reflected (feedback) at the laser end faces 9A and 9B, and is emitted from the laser end face 9A on the low reflection side at a certain oscillation wavelength.

  At this time, if the diffractive portion 10 exists in the vicinity of the laser end surface 9B, light guided in the waveguide (guided light) feels a periodic refractive index difference due to the diffractive portion 10, so that the active layer (pn junction) Layer) diffracts in a direction different from the X direction in a plane parallel to layer 4. In this case, since the photonic crystal is formed in a plane parallel to the active layer 4, the influence of the laser beam due to the periodic refractive index difference is vibration (longitudinal in the plane perpendicular to the active layer 4). (In other words, the greater the TM (Transverse Magnetic) component), the larger it becomes.

  Further, in the region where the photonic crystal is formed, the holes 11 are arranged at a constant period (interval) on the axis forming ± 45 degrees with respect to the X direction. It acts like a diffraction grating with periodicity in the direction of degrees. Therefore, in the vicinity of the laser end face 9B, as shown in FIG. 7A, a part of the light (guided light) traveling in the X direction toward the laser end face 9B is caused by a periodic refractive index difference due to the photonic crystal. And diffracted by 90 degrees in a direction different from the X direction, which is the original waveguide direction. Further, a part of the light diffracted in this way is diffracted by 90 degrees while feeling the periodic refractive index difference due to the photonic crystal again in the formation region of the photonic crystal. As a result, the light traveling direction is converted by 180 degrees so as to face the laser end face 9A side.

  Such diffraction of light occurs continuously in the formation region of the photonic crystal. Therefore, the light (guided light) incident on the photonic crystal region feels a periodic refractive index difference due to the photonic crystal and repeats diffraction of 90 degrees irregularly and repeatedly. Therefore, the light (guided light) incident on the photonic crystal formation region is distributed and fed back in a direction (stripe width direction) orthogonal to the X direction, as shown in FIG. 7B. At this time, a part of the light reaches the laser end face 9B through the photonic crystal region, and is reflected and fed back there.

  As a result, in the case of a conventional broad area type semiconductor laser, the laser beam reflected by the laser end face travels (reciprocates) only in the X direction. For example, as shown in FIG. When intense light is generated in a specific portion Pw (direction orthogonal to the X direction), this light travels (reciprocates) in the X direction at the same position in the stripe width direction. Therefore, since the laser light is emitted from the semiconductor laser in a state where the light intensity of a specific portion in the stripe width direction is larger than that of other portions, NFP is deteriorated.

  On the other hand, in the case of a broad area type semiconductor laser having a diffractive portion 10 made of a photonic crystal, the light traveling in the X direction is diffracted by the presence of the photonic crystal in the vicinity of the laser end face 9B, resulting in a stripe width. For example, as shown in FIG. 8B, even when intense light is generated in a specific portion Pw in the stripe width direction (direction orthogonal to the X direction), the light is dispersed in the stripe width direction. It spreads and spreads in the X direction (reciprocates). Therefore, the laser light is emitted from the semiconductor laser in a state where the light intensity of a specific portion in the stripe width direction is dispersed (distributed) to other portions, so that the NFP is good.

  In addition, when light is dispersed in the stripe width direction in the photonic crystal region, a plurality of longitudinal modes generated during laser oscillation influence each other. A specific mode becomes apparent. As a result, since the light guided in the waveguide converges to a wavelength having a limited spectrum, an optically advantageous effect that the overall spectrum width is reduced can be obtained. As a result, the monochromaticity of the laser light emitted from the semiconductor laser can be improved.

  In the above example, as a crystal structure of the photonic crystal, a square lattice in which holes 11 constituting lattice points are arranged in a square symmetry has been described as an example. A three-way lattice arranged in three-way symmetry may be adopted. When a three-dimensional lattice two-dimensional photonic crystal is employed, an equilateral triangle is formed when the three nearest holes (lattice points) 11 are connected. Therefore, a photonic crystal is formed in the diffraction section 10 in such a positional relationship that one side of the equilateral triangle is perpendicular to the X direction.

  When the photonic crystal having a trigonal lattice is formed in this way, the holes 11 are arranged at a constant period (interval) on the axis forming ± 30 degrees and the axis forming 90 degrees with respect to the X direction. Therefore, as shown in FIG. 9, a part of the light (guided light) traveling in the X direction toward the laser end face 9B feels a periodic refractive index difference due to the photonic crystal, and the original waveguide direction. Diffracts 60 degrees in a direction different from the X direction. Furthermore, a part of the light diffracted in this way is diffracted by 60 degrees in a region where the photonic crystal is formed, again feeling a periodic refractive index difference due to the photonic crystal. As a result, the light traveling direction is converted by 180 degrees so as to face the laser end face 9A side.

  Such diffraction of light occurs continuously in the formation region of the photonic crystal. Therefore, the light (guided light) incident on the photonic crystal region feels a periodic refractive index difference due to the photonic crystal and repeats diffraction of 60 degrees irregularly and repeatedly. Therefore, even when a photonic crystal having a crystal structure of a three-way lattice is adopted, light (guided light) incident on the formation region is distributed and fed back in a direction (stripe width direction) perpendicular to the X direction. The same effects as those obtained when a square lattice crystal structure is employed can be obtained.

  In the above example, a large number of holes 11 are regularly arranged in a constant cycle in the photonic crystal region constituting the diffractive portion 10, but for example as shown in FIG. As shown in FIG. 10B, by intentionally removing the holes (black circle portions) 11A for one row along the X direction at an arbitrary position in the stripe width direction (direction orthogonal to the X direction). In addition, a predetermined number (two in the illustrated example) of linear defect portions 14 having no holes may be provided.

  When such a configuration is employed, the linear defect portion 14 in the photonic crystal functions as a light waveguide. Therefore, when the light incident on the photonic crystal region is diffracted in a direction different from the X direction (90 degree direction and 60 degree direction), as shown in FIG. Most of the light travels along the linear defect portion 14. Thereby, the linear defect part 14 can be intentionally formed at an arbitrary position in the stripe width direction, and more light can be collected at the formation place.

  As a result, the NFP of the broad area type semiconductor laser can be made uniform. That is, in the case of a broad area type semiconductor laser, current tends to gather at the central portion in the stripe width direction due to its structure, so that the light intensity at that portion is larger than the other portions (edge portions in the stripe width direction). Become. On the other hand, by providing the linear defect portion 14 at the end in the stripe width direction, the light intensity at that portion becomes relatively large. Therefore, the light intensity distribution can be made more uniform in the stripe width direction.

  Moreover, in the said embodiment, although it was set as the structure which provided the diffraction part 10 in the vicinity of the laser end surface 9B, this invention is not restricted to this, The structure which provided the diffraction part 10 in the vicinity of the laser end surface 9A, and both It is good also as a structure which provided the diffraction part 10 in the vicinity of laser end surface 9A, 9B.

It is a figure which shows the structural example of the semiconductor laser which concerns on embodiment of this invention. It is a figure which shows the structural example of the diffraction part which consists of photonic crystals. It is a figure explaining the manufacturing method of the semiconductor laser which concerns on embodiment of this invention. It is sectional drawing which shows the other structural example of a semiconductor laser. It is a perspective view which shows the other structural example of the semiconductor laser to which this invention was applied. It is a figure explaining the other example of the manufacturing method of a semiconductor laser. It is a figure explaining the diffraction phenomenon of the light by a photonic crystal. It is the figure which compared the difference of the optical waveguide by the presence or absence of a diffraction part. It is a figure explaining the diffraction phenomenon of light at the time of employ | adopting a different crystal structure. It is a figure explaining the example of formation of a linear defect part. It is a figure explaining the state of the optical waveguide at the time of providing a linear defect part.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... n-type cladding layer, 3 ... n-type guide layer, 4 ... Active layer, 5 ... p-type guide layer, 6 ... p-type cladding layer, 9A, 9B ... Laser end face, 10 ... Diffraction part, 11 ... hole

Claims (3)

An optical waveguide is formed using the active layer and the two cladding layers, and among the laser end faces provided at both ends in the axial direction of the waveguide, in the vicinity of at least one laser end face, the Ri and light guided by said active layer in a plane parallel to name provided a diffractive portion diffracted in a different direction to the axial direction of the waveguide,
The diffraction part is made of a two-dimensional photonic crystal,
A semiconductor laser in which a linear defect is provided in the photonic crystal . The wavelength in the waveguide of the waveguide is an optical based on the value obtained by dividing the effective refractive index, obtained by setting the period of the refractive index distribution in the photonic crystal, a semiconductor laser according to claim 1, wherein. Comprising the crystal structure of the photonic crystal as a square lattice or trigonal lattice, the semiconductor laser according to claim 1, wherein.

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