Laser element with a photonic crystal layer and laser device

Abstract

A laser element (LD) comprising a photonic crystal layer (6) onto which laser light is incident, the photonic crystal layer (6) comprising: a first region consisting of a carrier layer (6A) formed from a medium having a first refractive index; and a plurality of second regions (6B), each formed from a medium having a second refractive index which has a refractive index different from that of the medium having a first refractive index, and which are arranged in the carrier layer (6A), wherein each region of the plurality of second regions (6B) has a planar shape of a triangle, an ellipse in which a numerical eccentricity is different from zero, or has a non-rotationally symmetric shape, wherein unit configuration regions (R11 - R34) are arranged two-dimensionally in an XY plane containing an X-axis and a Y-axis, each unit configuration region (R11 - R34) comprising exactly one second region (6B), wherein in each unit configuration region (R11 - R34), a rotation angle of a point on an outline of the planar shape with respect to a center point of the second region (6B) is denoted by φ, wherein an X-coordinate and a Y-coordinate of a center point (G) of each of the unit configuration regions (R11 - R34) are given by a center point of the associated second region (6B), wherein the angle of rotation φ increases proportionally to an increase in the X-coordinate of the unit configuration area (R11 - R34) at equal intervals and wherein the angle of rotation does not change despite a change in the Y-coordinate of the unit configuration area (R11 - R34), wherein a two-dimensional phase distribution of an image obtained by performing an inverse Fourier transform on an image in the far field corresponds to a distribution of the rotation angles φ at the locations of the unit configuration areas (R11 - R34), wherein the entire photonic crystal layer (6) contains at least three different rotation angles φ, wherein the laser element (LD) is configured such that a far-field pattern image of a laser beam is emitted in a state in which it is inclined with respect to a direction perpendicular to a light-emitting surface of the laser element (LD).

Description

Technical area

[0001] The present invention relates to a laser element and a laser device. State of the art

[0002] A photonic crystal layer used in a laser element of Patent Literature 1 is configured by periodically burying a plurality of regions with different refractive indices within a support layer, which becomes a carrier. The laser element includes two-layered photonic crystal layers. Each of the photonic crystal layers has the same periodically arranged patterns, but the patterns are different for each photonic crystal layer.

[0003] Patent Literature 2 discloses an example of a technique related to the linear polarization strength of a laser beam. According to Patent Literature 2, a plurality of circular regions with different refractive indices are conventionally embedded in the support layer constituting the photonic crystal layer, each at the lattice point of a square lattice. In this case, a problem has been raised that the polarization directions are not constant in a plane. That is, due to deterioration in the performance of a mode occurring within the photonic crystal layer, an electric field vector (a polarization direction) is generated to surround the periphery of each of the regions with different refractive indices.In this regard, Patent Literature 2 discloses a technique in which the deterioration of the mode performance is solved by arranging another region with a different refractive index at an asymmetric position deviating from the square grating, whereby it becomes possible to arrange the directions of the electric field vector as a whole. List of citationsPatent literature Patent literature 1 JP 2009 - 76900 A Patent literature 2 JP 2003 - 23193 A

[0004] A laser element with a two-dimensional photonic crystal layer is known from US 2011 / 0 188 526 A1, US 2009 / 0 135 871 A1 and US 2013 / 0 163 630 A1.

[0005] The article “Lasers producing tailored beams” (Miyai et al., Nature Brief Communications 441 (2006)) deals with photonic crystal layers for semiconductor lasers that can produce different beam shapes. Summary of the inventionTechnical problem

[0006] However, a conventional laser element cannot emit a laser beam in only one desired direction, so it is difficult to form a multi-directional laser output device.

[0007] The present invention has been made in an effort to solve the above-mentioned problems, and an object of the present invention is to provide a laser element and a laser device that can emit a laser beam only in a desired direction. Solution to the problem

[0008] To solve the above problems, the inventors, as a result of thorough research on a laser element structure, found that it is possible to emit laser beams with various patterns by constructing a shape of a region with a different refractive index in a photonic crystal layer and changing a rotation angle with respect to a center of a point on an outline of its plane shape according to coordinates. The plane shape is an approximate triangle, an approximate ellipse in which a numerical eccentricity is non-zero, or a non-rotationally symmetric shape, as a result of which an electric field vector remains without being displaced along a specific direction in the plane shape.

[0009] In addition, the approximate triangle or approximate ellipse is designed to have a triangle or ellipse but to include shapes that are somewhat distorted during manufacturing.

[0010] More specifically, the present invention provides a laser element according to claim 1.

[0011] Furthermore, the laser element may include: an active layer configured to emit the laser light; an upper and a lower cladding layer between which the active layer is located; and the photonic crystal layer arranged between the upper or lower cladding layer and the active layer.

[0012] Furthermore, a laser device may include: the laser element; and a polarizing plate arranged to face a light-emitting surface of the laser element. Advantageous effects of the invention

[0013] According to the laser element and the laser device of the present invention, it is possible to emit laser beams with various patterns. Short description of the drawing Fig. 1 is a diagram illustrating a configuration of a laser device. Fig. 2 is a sketch illustrating a configuration of a first laser element. Fig. 3 is a sketch illustrating a configuration of a second laser element. Fig. 4 is a sketch illustrating a configuration of a laser element body portion. Fig. Figure 5 is a sketch illustrating a longitudinal section configuration of a third laser element. Fig. 6 is a table showing a relationship between the material, a conductivity type, and a thickness (nm) of components constituting a laser element. Fig. Figure 7 is a sketch illustrating a longitudinal section configuration of a fourth laser element. Fig. Figure 8 is a top view of a photonic crystal layer. Fig. 9 is a diagram describing a positional relationship of regions with different refractive indices. Fig. Figure 10 is a diagram showing an intensity distribution pattern of emission light. Fig. 11 is a far-field image after the Fourier transform. Fig. Figure 12 is a diagram showing a positional relationship between regions with different refractive index and an electric field distribution. Fig. Figure 13 is a top view of a photonic crystal layer. Fig. Figure 14 is a diagram showing an intensity distribution pattern of emission light. Fig. 15 is a far-field image after the Fourier transform. Fig. Figure 16 is a diagram showing an intensity distribution pattern of emission light. Fig. 17 is a far-field image after the Fourier transform. Fig. Figure 18 is a diagram showing an intensity distribution pattern of emission light. Fig. 19 is a far-field image after the Fourier transform. Fig. Figure 20 is a diagram showing an intensity distribution pattern of emission light. Fig. 21 is a far-field image after the Fourier transform. Fig. Figure 22 is a diagram showing an intensity distribution pattern of emission light. Fig. 23 is a far-field image after the Fourier transform. Fig. Figure 24 is a diagram showing an intensity distribution pattern of emission light. Fig. 25 is a far-field image after the Fourier transform. Fig. Figure 26 is a diagram showing an intensity distribution pattern of emission light. Fig. 27 is a far-field image after the Fourier transform. Fig. Figure 28 is a sketch showing a longitudinal sectional configuration of a laser element. Fig. 29 are XY plane views showing shapes of respective regions 6B1 with different refractive index. Fig. 30 is a diagram showing a positional relationship between regions with different refractive index and an electric field distribution. Fig. Figure 31 is a diagram illustrating a mode delivered by a photonic crystal layer. Fig. 32 is a diagram illustrating a laser device including a laser element and a polarizing plate. Fig. 33 is a diagram illustrating main portions of a laser device including a polarizing plate and a lens. Description of embodiments

[0014] Exemplary embodiments of a laser element and a laser device are described below. The same reference numerals are used to denote the same structural elements, and redundant descriptions thereof are omitted.

[0015] Fig. 1 is a diagram illustrating a configuration of a laser device.

[0016] A plurality of laser elements LD are arranged one-dimensionally or two-dimensionally on a support plate SB. Each of the laser elements LD is driven by a drive circuit DRV provided in a rear surface or inside the support plate SB. That is, the drive circuit DRV supplies a drive current to each of the laser elements LD according to an instruction from a control circuit CONT. For example, the drive current is supplied to the two-dimensionally arranged laser elements LD according to a running sequence of addresses where the laser elements LD are arranged. A laser beam is emitted from the laser element LD in a direction perpendicular to the plate. When the laser elements LD are sequentially illuminated in the order of the addresses, the object is pseudo-scanned by the laser beam.A laser beam LB reflected by the target object can be detected by a photodetector PD such as a photodiode.

[0017] A detection signal indicating a laser beam intensity detected by the photodetector PD is input to the control circuit CONT. When the laser elements LD are pulse-driven, the photodetector PD can measure a time period from the emission time to the detection time of the laser beam, i.e., measure a distance to the target object.

[0018] The laser device can be used for the following purposes, for example. For example, the laser device can be used to emit the laser beam toward the target object and measure a distance to a laser beam irradiation point to measure a three-dimensional shape of the target object. When three-dimensional shape data is used, various machining devices or medical devices can use the three-dimensional shape data. In addition, it is possible to measure a distance according to a direction to an obstacle and use a brake or handle as a safety device that performs automatic control or assist control according to the distance when the laser beam is output in multiple directions to a moving object such as a vehicle.

[0019] The following describes the detailed structure of a laser element to be used in the aforementioned laser device. The laser element can emit light with various intensity patterns.

[0020] Fig. 2 is a sketch illustrating a configuration of a first laser element.

[0021] The laser element LD includes a photonic crystal layer (photonic crystal layer) 6 onto which laser light is incident. The laser light is incident into the photonic crystal layer 6 via an optical fiber F or directly from a laser element body LD1 such as a semiconductor laser element. The optical fiber F is fixed to a side surface of the photonic crystal layer 6. A plurality of optical fibers F may be provided. In this case, the laser light is incident into the photonic crystal layer 6 from the plurality of optical fibers F arranged along the side surface of the photonic crystal layer 6. The laser light incident into the photonic crystal layer 6 forms a predetermined mode according to a photonic crystal lattice of the photonic crystal layer 6 and is emitted outward in a direction perpendicular to a surface of the photonic crystal layer 6 as a laser beam LB.A reflection film RF made of metal such as aluminum is provided on a lower surface of the photonic crystal layer 6. The laser beam traveling toward the lower surface of the photonic crystal layer 6 is reflected by the reflection film RF and guided toward an upper surface of the photonic crystal layer 6. Thus, the intensity of the laser beam LB increases due to the reflection film RF.

[0022] Fig. 3 is a sketch illustrating a configuration of a second laser element.

[0023] The laser element LD is configured by placing the side surface of the aforementioned photonic crystal layer 6 directly adjacent to an end surface of an edge-emitting laser element body LD1. The side surface of the photonic crystal layer 6 can be fixed to the end surface of the laser element body LD1 using an adhesive or the like. Furthermore, it is possible to continuously form both the laser element body LD1 and the photonic crystal layer 6 from a semiconductor substrate by adjusting a thickness of the photonic crystal layer 6. The laser element body LD1 is configured by laminating a compound semiconductor layer. A first electrode E1 is provided on a lower surface of a corresponding laminate, and a second electrode E2 is provided on an upper surface of the laminate.By applying a drive current between the first electrode E1 and the second electrode E2, an active layer 4 of the laser element body LD1 emits light, and laser light L is incident on the photonic crystal layer 6. The incident laser light forms a predetermined mode within the photonic crystal layer 6 and emits a laser beam LB in a direction perpendicular to a substrate surface. A reflection film RF as described above is provided on a lower surface of the photonic crystal layer 6, achieving a similar effect to that described above.

[0024] Fig. 4 is a sketch showing a configuration of the above-mentioned laser element body LD1.

[0025] A lower cladding layer 2, a lower light guide layer 3, an active layer 4, an upper light guide layer 5, an upper cladding layer 7, and a contact layer 8 are sequentially layered on the semiconductor substrate 1. A first electrode E1 is provided on a lower surface of the semiconductor substrate 1, and a second electrode E2 is provided on an upper surface of the contact layer 8. When a drive current is supplied between the first electrode E1 and the second electrode E2, recombination of electrons and holes occurs within the active layer 4, causing the active layer 4 to emit light. Charge carriers intended to contribute to light emission and generated light are effectively confined by the upper and lower light guide layers 3 and 5 and by the cladding layers 2 and 7 therebetween.In addition, the first electrode E1 is provided on an entire lower surface of the semiconductor substrate 1, and the second electrode E2 is provided on a partial area of ​​an upper layer of the contact layer 8 in such a manner as to extend along a resonance length direction (an emission direction of the laser light L).

[0026] As described above, the laser light L emitted from the laser element body LD1 is incident on the photonic crystal layer 6.

[0027] Fig. Figure 5 is a sketch illustrating a longitudinal section configuration of a third laser element.

[0028] The laser element LD has a structure in which in a Fig. 4, a photonic crystal layer 6 is contained, forming a so-called emission laser with a photonic crystal surface.

[0029] The laser element LD contains an active layer 4, which generates laser light, an upper cladding layer 7 and a lower cladding layer 2, between which the active layer 4 is located, and light guide layers 3 and 5, which are arranged between the upper cladding layer 7 and the lower cladding layer 2 and between which the active layer 4 is located. The photonic crystal layer 6 is arranged between the upper cladding layer 7 and the active layer 4. In the Fig. In the structure shown in Figure 5, a second electrode E2 is provided in a central area of ​​a contact layer 8.

[0030] In the structure, the lower cladding layer 2, the lower light guide layer 3, the active layer 4, the upper light guide layer 5, the photonic crystal layer 6, the upper cladding layer 7, and the contact layer 8 are sequentially layered on a semiconductor substrate 1. A first electrode E1 is provided in a lower surface of the semiconductor substrate 1, and the second electrode E2 is provided in an upper surface of the contact layer 8. When a drive current is supplied between the first electrode E1 and the second electrode E2, recombination of electrons and holes occurs within the active layer 4, and the active layer 4 emits light. Charge carriers intended to contribute to light emission and generated light are effectively confined by the upper and lower light guide layers 3 and 5 and by the cladding layers 2 and 7 therebetween.

[0031] The laser light emitted from the active layer 4 enters the photonic crystal layer 6 and forms a predetermined mode. Furthermore, the photonic crystal layer 6 includes a support layer 6A formed from a medium having a first refractive index, and a plurality of different refractive index regions 6B formed from a second refractive index medium having a refractive index different from that of the first refractive index medium, and disposed within the support layer 6A. The plurality of different refractive index regions 6B include a periodic structure. The laser light incident into the photonic crystal layer 6 is emitted outward as a laser beam perpendicular to a substrate surface through the upper cladding layer 7, the contact layer 8, and the upper electrode E2.

[0032] Fig. 6 is a table showing a relationship between a material, a conductivity type, and a thickness (nm) of compound semiconductor layers constituting a laser element.

[0033] The materials of each element are as in Fig. 6. The semiconductor substrate 1 is made of GaAs, and the lower cladding layer 2 is made of AlGaAs. The lower light guide layer 3 is made of AlGaAs, the active layer 4 is made of a multiple quantum well structure MQV (barrier layer: AlGaAs / well layer: InGaAs), and the upper light guide layer 5 is made of an upper layer AlGaAs / a lower layer GaAs. In the photonic crystal layer (refractive index modulation layer) 6, the support layer 6A is made of GaAs, and the region 6B with a different refractive index (the buried layer) embedded in the support layer 6A is made of AlGaAs, the upper cladding layer 7 is made of AlGaAs, and the contact layer is made of GaAs.

[0034] It is noted that each of the layers, as in Fig. 6, is doped with impurities of a first conductivity type (N-type) or with impurities of a second conductivity type (P-type) (the impurity concentration is 1 10 17 up to 1 · 10 21 cm -3 ) and that an area not doped with any impurities is intentionally intrinsic (I-type). The concentration of I-impurities is 1 10 15 cm -3 or less.

[0035] In addition, an energy band gap of the cladding layer is set larger than an energy band gap of the light guide layer, and the energy band gap of the light guide layer is set larger than an energy band gap of a well layer of the active layer 4. In AlGaAs, it is easy to change the energy band gap and the refractive index by changing a composition fraction of Al. If a composition fraction X of Al with a relatively small atomic radius is changed into Al x Ga 1-xAs is decreased (increased), the energy band gap is decreased (increased) with a positive correlation with Al. When InGaAs is formed by mixing In with a large atomic radius with GaAs, the energy band gap decreases. That is, the Al composition ratio of the cladding layer is larger than the Al composition ratio of the light guide layer, and the Al composition ratio of the light guide layer is equal to or larger than the Al composition of a barrier layer (AlGaAs) of the active layer. The Al composition ratio of the cladding layer is set to 0.2 to 0.4, for example, 0.3. The Al composition ratios of the light guide layer and the active layer are set to 0.1 to 0.15, for example, 0.1.

[0036] In addition, the thicknesses of the layers are as in Fig. 6, where a range of numbers represents preferred values, and the numbers in parentheses indicate the optimal values. Incidentally, the photonic crystal layer is configured to change the polarization direction in the XY plane of the unit configuration regions and also to adjust the phases in the respective regions. Since the phase of the emitted laser light depends on the properties of the photonic crystal layer, the photonic crystal layer functions as a phase modulation layer.

[0037] As in Fig. 28, the photonic crystal layer 6 may be provided between the lower cladding layer 2 and the active layer 4. In this case, the photonic crystal layer 6 may be disposed at a position between the lower cladding layer 2 and the light guide layer 3. This structure also achieves the same effect as described above. That is, the laser light emitted from the active layer 4 is incident on the photonic crystal layer 6 and forms a predetermined mode. The laser light incident on the photonic crystal layer 6 is emitted as a laser beam through the lower light guide layer, the active layer 4, the upper light guide layer 5, the upper cladding layer 7, the contact layer 8, and the upper electrode E2 in a direction perpendicular to a substrate surface. The laser beam may also be emitted at an angle from the direction perpendicular to the substrate surface.

[0038] Fig. Figure 7 is a sketch illustrating a longitudinal section configuration of a fourth laser element.

[0039] Apart from a shape of an electrode, a structure of the laser element LD is essentially similar to that in Fig. 5. That is, a first electrode E1 provided in a lower surface of a semiconductor substrate 1 is an opening electrode having an opening in a central portion thereof, and an anti-reflection film M is provided inside and around an opening of the first electrode E1. The anti-reflection film M is formed of a single-layer dielectric film such as silicon nitride (SiN) or silicon dioxide (SiO2), or a multi-layer dielectric film. As the multi-layer dielectric film, a film formed by appropriately laminating two or more dielectric layers selected from a group of dielectric layers comprising, for example, silicon nitride (SiN) or silicon dioxide (SiO2) can be used. B. titanium dioxide (TiO2), silicon dioxide (SiO2), silicon monoxide (SiO), niobium oxide (Nb2O5), tantalum pentoxide (Ta2O5), magnesium fluoride (MgF2), titanium dioxide (TiO2), aluminum oxide (Al2O3), cerium dioxide (CeO2), indium oxide (In2O3) and zirconium dioxide (ZrO2).For example, for light with a wavelength of λ, a film with a thickness of λ / 4 is deposited as an optical thickness. In addition, a reflective film or an anti-reflective film can be formed by sputtering.

[0040] A second electrode E2 is provided on an upper surface of a contact layer 8. If necessary, an insulating film 9 is laminated on a surface different from the surface in which the contact electrode E2 is formed, protecting a rear surface.

[0041] In this structure, a lower cladding layer 2, a lower light guide layer 3, an active layer 4, an upper light guide layer 5, a photonic crystal layer 6, an upper cladding layer 7, and a contact layer 8 are sequentially layered on a semiconductor substrate 1. When a drive current is applied between the first electrode E1 and the second electrode E2, recombination of electrons and holes occurs within the active layer 4, causing the active layer 4 to emit light. Charge carriers contributing to light emission and generated light are effectively confined by the upper and lower light guide layers 3 and 5 and by the cladding layers 2 and 7 between them.

[0042] The laser light emitted from the active layer 4 enters the photonic crystal layer 6 and forms a predetermined mode. Furthermore, the photonic crystal layer 6 includes a support layer 6A formed from a medium having a first refractive index, and a plurality of different refractive index regions 6B formed from a second refractive index medium having a refractive index different from that of the first refractive index medium, and disposed within the support layer 6A. The plurality of different refractive index regions 6B have a periodic structure. The laser light incident on the photonic crystal layer 6 is emitted outward as a laser beam LB through the upper light guide layer 5, the active layer 4, the lower light guide layer 3, the lower cladding layer 2, the semiconductor substrate 1, and the anti-reflection film M.In a lower surface of the semiconductor substrate 1, the first electrode E1 is not provided in a region facing the second electrode E2, and the laser light LB is emitted outward from the lower surface. A region 6B with a different refractive index may be embedded within a hole of a support layer 6A, and then a coating layer with a changed refractive index, formed of the same material as the region 6B with a different refractive index, may be deposited on the support layer 6A.

[0043] Fig. 8 is a plan view of the above-mentioned photonic crystal layer 6.

[0044] The photonic crystal layer 6 includes the support layer 6A, formed from a medium with a first refractive index, and the region 6B with a different refractive index, formed from a medium with a second refractive index that has a refractive index different from that of the medium with a first refractive index. The region 6B with a different refractive index is a compound semiconductor but can be a hole filled with argon, nitrogen, or air.

[0045] A plurality of regions 6B having a different refractive index each have an XY plane having an approximate triangle, wherein the thickness direction of the plurality of regions 6B having a different refractive index is the Z axis.

[0046] The region 6B with a different refractive index forms a continuous figure, where a vertex location is denoted by 6B2 and a body portion within a hole is denoted by a region 6B1 with a different refractive index. In this case, unit configuration regions R11 to R34 are defined. Each of the unit configuration regions R11 to R34 is formed from a region 6B1 with a different refractive index. In the unit configuration regions R11 to R34, φ denotes a rotation angle of a point 6B2 on an outline (indicated on an outline by the black dot) with respect to the region 6B1 with a different refractive index (a center thereof). When the rotation angle φ coincides with the positive direction of the X-axis, φ = 0° is defined. In this case, the one point on the outline is set as the vertex of a triangle.

[0047] As in Fig. As shown in Figure 8, in the photonic crystal layer 6, the plurality of unit configuration regions R11 and R34 are arranged two-dimensionally on an XY plane including an X-axis and a Y-axis, and the XY coordinates of the unit configuration regions R11 and R34 are respectively given as the center points G of each of the first regions 6B1 having different refractive indexes. The XY coordinates (coordinates of the center G) of each of the unit configuration regions R11 and R34 are given as (X, Y).

[0048] The coordinates of the unit configuration area R11 are (X1, Y1) and the coordinates of the unit configuration area Rmn are (Xm, Yn) (where m and n are natural numbers). With reference to Fig. 8, the rotation angle φ increases proportionally to an increase in the coordinate on the X-axis at equal intervals, but it remains unchanged despite a change in the coordinate on the Y-axis. That is, the rotation angle φ is a function of X. The function is given, for example, as φ = φ0 + aX (where φ0 is an integer and a is an integer other than 0). In a light-emitting surface, a polarization modulation pattern is obtained corresponding to a location, but it is possible to enable conversion into an intensity modulation pattern by passing it through a polarizing plate. By performing Fourier transformation on the intensity modulation pattern by a convex lens, it is possible to obtain a beam spot with a desired shape. For example, it is possible to convert a laser beam shape into a spot (a circle).The function can be applied to the entire photonic crystal layer or to a specific area of ​​the photonic crystal layer.

[0049] Fig. 9 is a diagram for describing an example of a positional relationship of regions with different refractive index.

[0050] Fig. 9(A) represents the case φ = 0 (rad), Fig. 9(B) represents the case φ = 0.25π (rad), Fig. 9(C) represents the case φ = 0.5π (rad), Fig. 9(D) represents the case φ = 0.75π (rad), Fig. 9(E) represents the case φ = π (rad) and Fig. Figure 9(F) represents the case φ = 1.7π (rad).

[0051] Fig. Fig. 10 is a diagram showing an intensity distribution pattern of an emission light after passing through a polarizing plate P ( Fig. 33).

[0052] In Fig. 10, colors represent the intensity distribution (corresponding to φ) of laser light at any location (at all coordinates), with intensities from 0 to the maximum corresponding to black to white. Furthermore, an intensity corresponds to a polarization direction. A shape or a far-field image of the laser beam after it has passed through a lens or a hologram are, in this case, as in Fig. 11. A center of Fig. 10 corresponds to a direction perpendicular to the plane of the device, i.e., a direction perpendicular to the photonic crystal layer. A white portion corresponds to a shape of the laser beam. In this case, the shape of the laser beam is a spot (circle).

[0053] Fig. Figure 12 is a diagram showing a positional relationship between regions with different refractive index and an electric field distribution.

[0054] Fig. 12 shows plane states of four unit configuration regions R11, R12, R21, and R22 adjacent to each other. Within the photonic crystal layer 6, a mode is generated by laser light in which an electric field is distributed to surround the first refractive index region 6B1. It is known that, under the condition that a lattice interval is almost equal to one wavelength, in a structure in which the first refractive index regions 6B1 are arranged in a square lattice shape, four types of modes are generated from their symmetry. Since the four types of modes have different frequencies, by appropriately selecting a frequency of the light incident on the photonic crystal layer, the mode in which the electric field is distributed to surround the first refractive index region 6B1 is as described above.In this mode, each of the electric field vectors indicated by arrows is arranged to rotate around the center G. The center points G of the regions 6B1 with different refractive indices coincide with the center points of these electric field vectors, and a square is configured by a line connecting the center points G of four regions 6B1 with different refractive indices. That is, the regions 6B with different refractive indices are arranged at lattice points of a square lattice. In addition, there is an electric field vector that rotates around the intersection points of the configured square diagonals.

[0055] If there is a peak point 6B2 in each of the unit configuration regions, it is likely that effectively only one electric field vector remains and acts in a specific direction, and that the remaining electric field vector is offset with respect to the single peak. According to the boundary conditions of Maxwell's equations, electric field components in the XY plane vary depending on the dielectric constant difference between the inner and outer surfaces of a refractive index boundary. As a result, a spatial phase modulation is caused. That is, only the electric field vector (polarization direction) passing through the single peak point 6B2 remains as a point light source of linearly polarized light.In other words, it can be considered that multiple point light sources with different polarization directions are distributed in a two-dimensional plane on the photonic crystal layer 6. Furthermore, it can be considered that by performing a Fourier transform on the point light sources, a far-field image of the distribution of the point light sources is obtained.

[0056] In this case, a planar shape of the region 6B1 with a different refractive index may have an approximate triangle with the following shape and with a polarization direction.

[0057] When the plane shape is an equilateral triangle or an isosceles triangle with a bottom side shorter than the other two sides, a polarization component (an electric field vector) remains in a direction perpendicular to a direction from the bottom to a vertex. In the case of an isosceles right-angled triangle, a polarization component remains parallel or perpendicular to a hypotenuse. In the case of a right-angled triangle, a polarization component remains parallel to a hypotenuse or a polarization component perpendicular to the hypotenuse. Since a polarization azimuth (a phase) is changed according to the shape as described above, it is possible to change a phase of the laser light by rotating each region with a different refractive index around a thickness direction (Z-axis) of the photonic crystal layer.

[0058] Fig. Figure 13 is a top view of a photonic crystal layer.

[0059] The Fig. 13 The image shown differs from that shown in Fig. 8 by the fact that φ is a function of Y as well as a function of X. That is, φ increases proportionally to an increase in X at equal intervals, and φ also increases proportionally to an increase in Y at equal intervals. The function is given as φ = φ0 + aX + bY (φ0 is an integer, a is an integer other than 0, and b is an integer other than 0). The function can be applied to the entire photonic crystal layer or to a specific area of ​​the photonic crystal layer.

[0060] Fig. Figure 14 is a diagram showing an intensity distribution pattern of emission light after passing through a polarizing plate.

[0061] In Fig. 14, colors represent the intensity distribution (corresponding to φ) of laser light at any location (all coordinates), with intensities from 0 to the maximum corresponding to black to white. In this case, for example, in Fig. 15 shows a shape or a far-field image of the laser beam after it has passed through a lens or a hologram. A center of Fig. 14 corresponds to a spot emanating from a center of a light-emitting surface of a device in a vertical direction, that is, a spot emanating from a center of the photonic crystal layer in a vertical direction. A white portion corresponds to a shape of a laser beam. In this case, the shape of the laser beam is a spot (circle).

[0062] Furthermore, by using a method according to the present invention, it is possible to realize a specific phase distribution. In other words, it is possible to realize a cluster of point light sources having a specific intensity distribution. Since a far-field image obtained from the cluster of point light sources is obtained by performing Fourier transform on an intensity distribution of the point light sources, a specific far-field image can be obtained if a specific intensity distribution is realized. More specifically, a specific far-field image can be obtained if the phase distribution obtained by performing Fourier transform on a desired far-field image is designed according to a method of the present invention. Examples of an intensity distribution pattern are described below.

[0063] Fig. Figure 16 is a diagram showing an intensity distribution pattern of emission light.

[0064] In Fig. 16, colors represent the intensity distribution (corresponding to φ) of laser light at any location (all coordinates), with intensities from 0 to the maximum corresponding to black to white. In this case, a shape or far-field image of the laser beam after passing through a lens or through a hologram such as in Fig. 17. A center of Fig. 16 corresponds to a position emanating from a center of a light-emitting surface of a device in a vertical direction, that is, a position emanating from a center of the photonic crystal layer in a vertical direction. A white portion corresponds to a laser beam shape. In this case, it is possible to obtain a laser beam with a line pattern along a Y-axis direction.

[0065] Fig. Figure 18 is a diagram showing an intensity distribution pattern of emission light.

[0066] In Fig. 18, colors represent the intensity distribution (corresponding to φ) of laser light at any location (all coordinates), with intensities from 0 to the maximum corresponding to black to white. In this case, a shape or far-field image of the laser beam after passing through a lens or through a hologram such as in Fig. 19. A center of Fig. 18 corresponds to a point emanating from a center of a light-emitting surface of a device in a vertical direction, that is, a point emanating from a center of the photonic crystal layer in a vertical direction. A white portion corresponds to a laser beam shape. In this case, it is possible to obtain a laser beam with a ring-shaped pattern.

[0067] Fig. Figure 20 is a diagram showing an intensity distribution pattern of emission light.

[0068] In Fig. 20, colors represent the intensity distribution (corresponding to φ) of laser light at any location (all coordinates), with intensities from 0 to the maximum corresponding to black to white. In this case, a shape or far-field image of the laser beam after passing through a lens or through a hologram such as in Fig. 21. A center of Fig. 20 corresponds to a point emanating from a center of a light-emitting surface of a device in a vertical direction, that is, a point emanating from a center of the photonic crystal layer in a vertical direction. A white portion corresponds to a shape of a laser beam. In this case, it is possible to obtain a three-point multi-spot laser beam.

[0069] Fig. Figure 22 is a diagram showing an intensity distribution pattern of emission light.

[0070] In Fig. 22, colors represent the intensity distribution (corresponding to φ) of laser light at any location (all coordinates), with intensities from 0 to the maximum corresponding to black to white. In this case, a shape or far-field image of the laser beam after passing through a lens or through a hologram such as in Fig. 23. A center of Fig. 22 corresponds to a point emanating from a center of a light-emitting surface of a device in a vertical direction, that is, a point emanating from a center of the photonic crystal layer in a vertical direction. A white portion corresponds to a shape of a laser beam. In this case, it is possible to generate a laser beam with a character shape for " (Light)".

[0071] Fig. Figure 24 is a diagram showing another phase distribution pattern of a region with a different refractive index.

[0072] In Fig. 24, colors represent an intensity distribution (corresponding to φ) of laser light at any location (all coordinates), with intensities from 0 to the maximum corresponding to black to white. In this case, a shape or far-field image of the laser beam after passing through a lens or through a hologram such as in Fig. 25. A center of Fig. 24 corresponds to a point emanating from a center of a light-emitting surface of a device in a vertical direction, that is, a point emanating from a center of the photonic crystal layer in a vertical direction. A white portion corresponds to a laser beam shape. In this case, it is possible to obtain a double-ring-shaped laser beam.

[0073] Fig. Figure 26 is a diagram showing an intensity distribution pattern of emission light.

[0074] In Fig. 26, colors represent the intensity distribution (corresponding to φ) of laser light at any location (all coordinates), with intensities from 0 to the maximum corresponding to black to white. In this case, a shape or far-field image of the laser beam after passing through a lens or through a hologram such as in Fig. 27. A center of Fig. 26 corresponds to a point emanating from a center of a light-emitting surface of a device in a vertical direction, that is, a point emanating from a center of the photonic crystal layer in a vertical direction. A white portion corresponds to a shape of a laser beam. In this case, it is possible to obtain a vector beam called a Laguerre-Gaussian beam.

[0075] As described above, a far-field image after the Fourier transformation of a laser beam can have various shapes such as a single-point or multi-point shape, a ring shape, a linear shape, a character shape, a double-ring shape, or a Laguerre-Gaussian beam shape.

[0076] As described above, in the case of the above-mentioned structure, a change in the laser light from the respective regions 6B (6B1) with different refractive index occurs, so that an intensity in a specific direction increases. That is, a specific polarization is caused. Here, since the rotation angle φ from a center toward a point on an outline of the planar shape is a function of the coordinates, a polarization direction of each laser light (an intensity after passing through a polarizing plate) changes when spatial coordinates are changed. Thus, it is possible to regard each of the regions with different refractive index as a point light source, and it is possible to change its intensity for each coordinate according to a position of the rotation angle φ. If it is possible to adjust the intensity of each of the point light sources distributed two-dimensionally, it is possible to emit various laser beam patterns.

[0077] As described above, a far-field image of a point light source group distributed two-dimensionally can be regarded as a Fourier transform image of a point light source group. In the case of configuring a circular laser beam spot by Fourier transform, an intensity of each point light source can be adjusted by performing an inverse Fourier transform of the circle at a specific location. That is, if each rotation angle φ is adjusted accordingly to an intensity of each point light source in the case of performing the inverse Fourier transform of the circle at a specific location, it is possible to obtain a circular laser beam spot at the specific location. In other words, it is possible to obtain a spot with a two-dimensional single-mode intensity distribution at a location in an oblique direction.

[0078] Furthermore, the laser beam emission angles are different. The above-mentioned laser device includes any one of the above-mentioned plurality of laser elements arranged one-dimensionally or two-dimensionally, and a drive circuit that drives the laser element and outputs a laser beam in a plurality of directions. The device can function as a pseudo-laser beam scanning device.

[0079] Although each of the regions 6B1 with a different angle of refraction has been described as having an approximate triangle, each of the regions 6B1 with a different refractive index may have an approximate ellipse in which a numerical eccentricity is non-zero. The approximate triangle or ellipse is designed to have a triangle or ellipse, but is intended to include shapes that are somewhat distorted during manufacture.

[0080] Fig. 29 are XY-plane views showing shapes of respective regions 6B1 with different refractive index. As in Fig. 29(A), the region 6B1 with a different refractive index within a hole of the support layer 6A may have a suitable elongated isosceles triangle. In this case, the electric field strength increases in a polarization direction from the bottom to the apex 6B2. As shown in Fig. 29(B), the different refractive index region 6B1 within the hole of the support layer 6A may have an approximately elongated ellipse in which a numerical eccentricity is different from zero. In this case, the electric field strength increases in a polarization direction along a principal axis. In addition, when the different refractive index region 6B1 within the hole of the support layer 6A has a non-rotationally symmetric shape such as a combined shape of a triangle and a rectangle as shown in Fig. 29(C). In the case of Fig. 29 the electric field strength increases in a longitudinal direction (X-axis direction).

[0081] If the areas with different refractive index as described above are of the flat shape as in Fig. 8 or Fig. 13 are arranged two-dimensionally, the electric field vector guiding the one point 6B2 remains on the outline, so that it is possible to emit a laser beam only in a diagonal direction by forming the phase distribution as described above.

[0082] Among the above-mentioned structures, the structure including the active layer 4 and the photonic crystal layer 6 has freedom in terms of material system, thickness, and layer configuration. When fabricating the laser element, each compound semiconductor layer is formed by metal organic chemical vapor deposition (MOCVD). Crystal growth is performed in a (001) plane of the semiconductor substrate 1, but the present invention is not limited thereto. When fabricating a laser element using the above-mentioned AlGaN, a growth temperature of AlGaAs is in a range of 500°C to 850°C, with a temperature of 550°C to 700°C used in the experiment.During growth, TMA (trimethylaluminum) is used as an Al precursor, TMG (trimethylgallium) and TEG (triethylgallium) are used as gallium precursors, AsH3 (arsine) is used as an As precursor, Si2H6 (disilane) is used as an N-type impurity precursor, and DEZn (diethylzinc) is used as a P-type impurity precursor. In GaAs growth, TMG and arsine are used, while TMA is not. InGaAs is fabricated using TMG, TMI (trimethylindium), and arsine. The formation of an insulating film can be achieved by sputtering onto a target using its composition materials as precursors.

[0083] That is, the above-mentioned laser element is fabricated by sequentially and epitaxially growing an N-type cladding layer (AlGaAs) 2, a guide layer (AlGaAs) 3, a multi-quantum well structure (InGaAs / AlGaAs) 4, a light guide layer (GaAs / AlGaAs) 5, and a support layer (GaAs) 6A using MOCVD (metal organic chemical vapor deposition) on an N-type semiconductor substrate (GaAs) 1. To achieve alignment after epitaxial growth, a SiN layer is subsequently formed on the support layer 6A, and then a resist is formed on the SiN layer using the PCVD (plasma CVD) method. Furthermore, the resist is exposed and developed, and the SiN layer is etched using the resist as a mask, causing the SiN layer to partially remain to form an alignment mark. The remaining resist is removed.

[0084] Subsequently, a separate resist is coated on the support layer 6A, and a two-dimensional thin pattern is drawn and developed on the resist using an alignment mark as a reference by an electron beam drawing device, whereby the two-dimensional thin pattern is formed on the resist. After that, the two-dimensional thin pattern is transferred to the support layer 6A with a depth of about 100 nm by dry etching using the resist as a mask to form a hole (a via), and the resist is removed. The depth of the hole is 100 nm. Within the hole, a compound semiconductor, which becomes the different refractive index region 6B (AlGaAs), is regrowth to a depth greater than the hole.An upper cladding layer (AlGaAs) 7 and a contact layer (GaAs) 8 are sequentially formed by MOCVD, and a suitable electrode material is formed on the upper and lower surfaces of the substrate by a deposition method or a sputtering method, thereby forming the first and second electrodes. Furthermore, if necessary, an insulating film can be formed on the upper and lower surfaces of the substrate by a sputtering method or the like.

[0085] When the photonic crystal layer is deposited under the active layer, the photonic crystal layer can be formed on the lower cladding layer before the formation of the active layer and the lower light guide layer.

[0086] In the case of manufacturing a laser element body that does not include a photonic crystal layer, this manufacturing process can be omitted. Furthermore, a columnar region of air with a different refractive index can be prepared as a cavity, and air or a gas such as nitrogen or argon can be filled therein. Furthermore, in the above-mentioned square grating, an interval between vertical and horizontal grating lines is a degree obtained by dividing a wavelength by an equivalent refractive index, and more specifically, it is preferably set to about 300 nm. Furthermore, it is possible to arrange the region with a different refractive index at a lattice point location in a triangular lattice instead of at a lattice point location in a square lattice.In the case of the triangular grating, an interval between the horizontal and oblique grating lines is approximately obtained by dividing a wavelength by an equivalent refractive index and further by dividing the wavelength by sin 60°, more specifically, it is preferably set to about 350 nm.

[0087] If the unit vectors of orthogonal coordinates are set to x and y in the case of a square lattice with a lattice interval a, the translational basis vectors a1 = ax, a2 = ay, and the reciprocal lattice basis vectors for the translational vectors a1 and a2 are b1 = (2π / a)y and b2 = (2π / a)x. If a wavenumber vector in an energy band gap of the photonic crystal is k = nb1 + mb2 (where n and m are arbitrary integers), it is possible to obtain a resonant mode (a standing wave in the XY plane) in which a wavenumber vector k becomes a Γ point, with the lattice interval a equal to a wavelength λ. In addition, mode A is a mode in which the lowest frequency is delivered, and mode B is a mode in which the second lowest frequency is delivered.

[0088] In addition, a polarizing plate is used to perform intensity modulation of the in-plane electromagnetic field distribution of a standing wave in the aforementioned photonic crystal layer (in-plane polarity distribution of a point light source). Afterward, a shape obtained by performing Fourier transformation can be formed into not only a single-mode beam (spot), but also, as described above, a character shape, a group of two or more spots with the same shape, a vector beam, or the like.

[0089] It is preferable that the refractive index of the support layer 6A be in a range of 3.0 to 3.5, and that the refractive index of the region 6B with a different refractive index be in a range of 1.0 to 3.4. Furthermore, it is preferable that the regions 6B1 with a different refractive index within the holes of the support layer 6A have an average maximum diameter in the range of 38 nm to 76 nm.

[0090] Furthermore, in the case of a non-rotationally symmetric shape, it is preferable that the average maximum diameter can have three or more values ​​when φ along the X-axis direction is in the range of more than 0 and less than 2π (rad).

[0091] As described above, any laser element as described above is also a laser element including a photonic crystal layer onto which a laser beam is incident, and a plurality of regions with different refractive index in the photonic crystal layer have a planar shape that is an approximate triangle, an approximate ellipse in which a numerical eccentricity is non-zero, or a non-rotationally symmetric shape. Furthermore, the rotation angles φ vary depending on a location (coordinates), and at least three different rotation angles φ are included in the entire photonic crystal layer when the XY coordinates of the unit configuration region are (X, Y). According to the rotation angle φ, a phase difference is caused, so that a laser beam in a desired direction can be obtained.The rotation angle φ is a function of X or a function of X and Y in the entire photonic crystal layer or in a specific area thereof and can form a spot.

[0092] A cluster of spots can form a more complicated shape. In the above-mentioned laser element, a far-field pattern image of the laser beam emitted in a state where it is tilted from a direction perpendicular to a light-emitting surface of the laser element has a single-spot or multi-spot shape, a ring shape, a linear shape, a character shape, a double-ring shape, or the Laguerre-Gaussian beam shape. Furthermore, a two-dimensional phase distribution of the image obtained by performing inverse Fourier transform on the far-field corresponds to a distribution of the rotation angles φ of the one points 6B2 on the outlines of the regions with different refractive index at the positions of the unit configuration regions.

[0093] Furthermore, the depths (thicknesses) of the regions 6B with different refractive indices forming the photonic crystal layer can be the same or different from each other in the XY plane. When the depths are different, a refractive index is changed. Thus, by adjusting the depths of the regions 6B with different refractive indices, it is possible to change a phase of the emission light.

[0094] Fig. 30 is a graph showing locations of regions with different refractive indices.

[0095] With respect to a center G of the region 6B1 with a different refractive index, one point 6B2 (the vertex) on the contour is located at a position (x, y). The angle between the vertex 6B2 and the x-axis is φ(x, y).

[0096] In this case, an intensity I of the laser light after passing through a polarizing plate is represented by the following equation. I(x, y)∝f(x, y)⋅g(φ, θ)⋅h(FF)⋅p(X, Y)=f(x,y)⋅g{φ(x, y),θ}⋅h(FF)⋅p(X, Y)

[0097] A detailed description is given below.

[0098] f(x, y) is a function representing a change in intensity according to an inter-unit grid arrangement location (x, y) of the one point 6B2 (vertex) on the contour.

[0099] Fig. Figure 31 is a diagram illustrating a mode provided by the photonic crystal layer. With reference to

[0100] Fig. 31, the theoretical electric field distributions in a square lattice structure are mode 1 to mode 4. In a configuration where light is introduced from the outside into the photonic crystal layer, modes 1 to mode 4 have different resonance frequencies, so a mode can be selected according to a wavelength of the introduced light. In this case, an easily treatable mode is mode 1 or mode 2.

[0101] Furthermore, in a configuration where an area near the center of the different refractive index region 6B1 serves as a resonator for oscillation, mode 3 and mode 4 cause large light leakage from the resonator and have a very low possibility of oscillation, so that either mode 1 or mode 2 has a possibility of oscillation. Accordingly, it is possible to assume mode 1 or mode 2.

[0102] In the case of Mode 1 ( Fig. 31(A)), an amplitude of a magnetic field is measured at a location on the surface near the center of the region 6B1 with a different refractive index (a location A in Fig. 32(A)) to the maximum. In addition, an amplitude of a magnetic field at points spaced from the positions by one half of the grid interval in the x-direction and in the y-direction (a position B in Fig. 31(A)), to the maximum. The magnetic fields of A and B have phases shifted from each other by π. When A and B are called an antinode of the magnetic field, electric fields exist such that they surround the antinode of the magnetic field. At a certain moment, the orientation of an electric field surrounding A and the orientation of an electric field surrounding B are opposite to each other. Furthermore, an amplitude of the electric field in a midsection of a line connecting A and B, which are adjacent to each other, becomes the maximum value. Furthermore, the amplitudes of the electric field in a midsection of a line connecting A and A, which are adjacent to each other, and in a midsection of a line connecting B and B, which are adjacent to each other, become zero.

[0103] In the case of Mode 2 ( Fig. 31(B)), the electromagnetic field distribution is distributed because the electromagnetic field distribution of mode 1 is shifted by half a grating interval in the x-direction or the y-direction. The electromagnetic field distributions of mode 1 and mode 2 have the characteristics described above. f(x, y) changes depending on the electric field strength in a section where the region near the center of the different refractive index area 6B1 is located.

[0104] g(φ, θ) is a function indicating a change in intensity due to a polarization direction φ from the center G to a position of one point 6B2 on the contour and a transmission axis direction θ of a polarizing plate (where f is changed by a position (x, y)). When the transmission axis direction θ of the polarizing plate is equal to a polarization direction at φ(x, y), a transmittance becomes high and the intensity increases.

[0105] More precisely, g(φ,θ) = I0cos 2 (θ - φ). In this case, I0 is a value determined by the light loss due to the polarizing plate, and it corresponds to the transmittance of the polarizing plate in the case of θ = φ. φ is the polarization direction of the output light at the one point 6B2 on the contour, and θ is a transmission axis direction of the polarizing plate.

[0106] h(FF) is a function that represents a change in intensity caused by a position of the one point 6B2 on the contour.

[0107] As described above, the electric field distribution of Mode 1 or Mode 2 is a possible option. A triangle is an asymmetric figure where no destructive interference occurs. The electric field in the xy plane changes depending on the difference in the dielectric constant between the inside and outside of the hole. That is, an asymmetry-induced component of the electric field causes diffraction in the Z direction. The change due to the asymmetry of the electric field in the xy plane, which depends on a change in the aperture, is defined as ha(FF). In addition, FF is a filling factor and refers to the ratio of the area occupied by the region 6B with a different refractive index to that occupied in a unit lattice.

[0108] p(X, Y) is an intensity distribution function at the position (X, Y) in the photonic crystal layer. Using the wave theory of optical coupling disclosed in Y. Liang et al., "Three-dimensional coupled-wave analysis for square-lattice photonic crystal surface emitting lasers with transverse-electric polarization: finite size effects," Opt Express 20, 15945-15961 (2012), it is possible to calculate an envelope intensity distribution of the entire element.

[0109] Fig. 32 is a diagram illustrating a laser device including a laser element and a polarizing plate.

[0110] Laser light with a plurality of polarization directions Dp is emitted from a light emission surface of the laser element LD ( Fig. 32 (A)). The laser light is intensity modulated by passing through the polarization plate P. Fig. 32(B). That is, the laser device includes the above-mentioned laser element LD and a polarizing plate P facing a light-emitting surface of the laser element LD.

[0111] In the aforementioned laser element, the position of the single point 6B2 on the contour differs between the respective unit gratings, so that light with different polarizations can be obtained for the respective unit gratings. Accordingly, by combining a polarizing plate on an emission side, it is possible to obtain plane waves whose intensities are different while the phases are aligned with respect to the unit gratings.

[0112] In the aforementioned laser element, a plane wave with different intensities for each unit grating is obtained as emission light. In other words, a plane wave with different intensities for each location is obtained as emission light. By obtaining the plane wave with different intensities for each location, it is possible to obtain a hologram using the method described in WH Lee, "Sampled Fourier transform hologram generated by computer," Appl. Opt. 9, 639-643 (1970). Thus, it is possible to obtain a specific beam pattern.

[0113] If an example is described according to a specific procedure, for example, a desired beam pattern, i.e., two-dimensional angular intensity information, is prepared as a two-dimensional array, and a two-dimensional discrete Fourier transform or a two-dimensional fast Fourier transform is performed on the two-dimensional angular intensity information, thereby obtaining a two-dimensional array with a complex amplitude. In this case, the number of elements of the two-dimensional array of the angular intensity information of an originally prepared beam pattern is equal to the number of elements of the two-dimensional array with the complex amplitude after the transformation. The complex amplitude of each element is composed of a real part and an imaginary part, where the real part and the imaginary part have positive and negative values, respectively.

[0114] According to the method of the above-mentioned Lee literature, four divided stripe-shaped regions with the same width correspond to a complex amplitude as described above, and intensities of the divided regions are assigned according to the following procedure. In this case, the stripe-shaped regions are defined sequentially from the left as a first region, a second region, a third region, and a fourth region. When a real part of the above complex amplitude has a positive value, the first region is assigned a value of the real part of the complex amplitude, and the third region is assigned zero. When the real part of the above complex amplitude has a negative value, the first region is assigned zero, and the third region is assigned an absolute value of the value of the real part of the complex amplitude. When the real part of the complex amplitude is 0, the first region and the third region are assigned 0.In addition, if an imaginary part of the above complex amplitude has a positive value, the second region is assigned a value of the imaginary part of the complex amplitude, and zero is assigned to the fourth region. If the imaginary part of the above complex amplitude has a negative value, zero is assigned to the second region, and an absolute value of the value of the imaginary part of the complex amplitude is assigned to the fourth region. If the imaginary part of the complex amplitude is 0, 0 is assigned to the second region and the fourth region. The values ​​assigned as described above are all negative values, whereby it is possible to perform a correspondence of the intensity distributions.

[0115] After the intensity distributions have been assigned to respective striped regions according to the above-mentioned procedure, a location of the one point 6B2 on the outline is assigned in such a way that a desired intensity distribution is obtained. That is, according to the function g(φ, θ) representing an intensity change due to the polarization direction φ on the outline and the transmission axis direction θ of the polarization plane at the location of the one point 6B2 on the outline, the intensity distribution at locations is converted into the arrangement of the one points 6B2 on the outline. According to the above-mentioned procedure, it is possible to obtain an arrangement of the one points 6B2 on the outline for obtaining a desired beam pattern.

[0116] Although Lee's method is provided as the method for determining the arrangement of the single points 6B2 on the outline from a desired beam pattern, the present invention is characterized in that a specific intensity distribution is obtained in which phases are aligned by the arrangement of the single points 6B2 on the outline. Methods other than Lee's method can be considered as a method for determining the arrangement of the single points 6B2 on the outline. Although a method for assigning intensity distributions to three stripe-shaped regions and obtaining a result similar to Lee's method is disclosed in CB Burckhardt, "A simplification of Lee's method of generating holograms by computer," Appl. Opt 9, 1949 (1970), for example, this method may be used, or another method capable of obtaining equivalent results may be used.

[0117] Fig. 33 is a diagram illustrating main portions of a laser device including a polarizing plate P and an optical element LS. That is, it is possible to arrange the optical element LS, such as a lens or a hologram, in a subsequent stage of the polarizing plate P. The optical element LS can perform Fourier transformation on incident laser light and output the laser light. List of reference symbols

[0118] 6 ... photonic crystal layer, 6A ... carrier layer, 6B, 6B1 ... region with different refractive index, 6B2 ... a point on the outline

Claims

[1] Laser element (LD) comprising a photonic crystal layer (6) onto which laser light is incident, the photonic crystal layer (6) comprising: a first region consisting of a carrier layer (6A) formed from a medium having a first refractive index; and a plurality of second regions (6B), each formed from a medium having a second refractive index which has a refractive index different from that of the medium having a first refractive index, and which are arranged in the carrier layer (6A), wherein each region of the plurality of second regions (6B) has a planar shape of a triangle, an ellipse in which a numerical eccentricity is different from zero, or has a non-rotationally symmetric shape, wherein unit configuration regions (R11 - R34) are arranged two-dimensionally in an XY plane containing an X-axis and a Y-axis, each unit configuration region (R11 - R34) comprising exactly one second region (6B), wherein in each unit configuration region (R11 - R34), a rotation angle of a point on an outline of the planar shape with respect to a center point of the second region (6B) is denoted by φ, wherein an X-coordinate and a Y-coordinate of a center point (G) of each of the unit configuration regions (R11 - R34) are given by a center point of the associated second region (6B), wherein the angle of rotation φ increases proportionally to an increase in the X-coordinate of the unit configuration area (R11 - R34) at equal intervals and wherein the angle of rotation does not change despite a change in the Y-coordinate of the unit configuration area (R11 - R34), wherein a two-dimensional phase distribution of an image obtained by performing an inverse Fourier transform on an image in the far field corresponds to a distribution of the rotation angles φ at the locations of the unit configuration areas (R11 - R34), wherein the entire photonic crystal layer (6) contains at least three different rotation angles φ, wherein the laser element (LD) is configured such that a far-field pattern image of a laser beam is emitted in a state in which it is inclined with respect to a direction perpendicular to a light-emitting surface of the laser element (LD). [2] Laser element (LD) according to claim 1, further comprising: an active layer (4) configured to emit the laser light; an upper and a lower cladding layer (7, 2), between which the active layer (4) lies; and the photonic crystal layer (6) arranged between the upper or lower cladding layer (7, 2) and the active layer (4). [3] Laser device comprising: a laser element (LD) according to one of claims 1 or 2; and a polarizing plate (P) arranged to face a light-emitting surface of the laser element (LD).

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