Semiconductor light-emitting element

Abstract

To provide a semiconductor light-emitting element that can reduce stray light. [Solution] The semiconductor light-emitting element 1A comprises a semiconductor stack 20, an electrode portion 16, and an electrode portion 17. The semiconductor stack 20 includes an active layer 12 and a phase modulation layer 15. The phase modulation layer 15 has a plurality of phase modulation regions 151. Each phase modulation region 151 includes a basic region 15a having a first refractive index and a plurality of different refractive index regions 15b having a second refractive index different from the first refractive index and distributed in two dimensions. The electrode portion 16 includes a plurality of electrodes 161 that overlap with the plurality of phase modulation regions 151 when viewed from the stacking direction of the semiconductor stack 20. The plurality of electrodes 161 are electrically isolated from each other. Laser light L that resonates in each of the plurality of phase modulation regions 151 is emitted through the second surface 20b. The semiconductor light-emitting element 1A has a reflection reduction structure 41 configured to reduce the reflection of light emitted from each phase modulation region 151 at the electrode portion 16.

Description

[Technical Field]

[0001] This disclosure relates to a semiconductor light-emitting element. [Background technology]

[0002] Patent Document 1 discloses a semiconductor light-emitting element capable of dynamically changing the output optical image. This semiconductor light-emitting element comprises a semiconductor stack, a first electrode, and a second electrode. The semiconductor stack has a stacked structure including an active layer and a phase modulation layer between a first surface and a second surface. The phase modulation layer has a plurality of phase modulation regions arranged along a virtual plane perpendicular to the thickness direction of the phase modulation layer and optically coupled to one another. Each of the plurality of phase modulation regions includes a basic region having a first refractive index and a plurality of regions with different refractive indices. The plurality of regions with different refractive indices are provided within the basic region, have a second refractive index different from the first refractive index, and are distributed two-dimensionally along the plane. The first electrode faces the first surface of the semiconductor stack. The second electrode faces the second surface of the semiconductor stack. One or both of the first electrode and the second electrode include a plurality of electrode portions that overlap with the plurality of phase modulation regions when viewed from the stacking direction of the semiconductor stack. The plurality of electrode portions are electrically isolated from each other. Light emitted from the active layer resonates in each of the multiple phase modulation regions of the phase modulation layer, and from each of these multiple phase modulation regions, it is projected onto a common irradiation area located in a direction intersecting both the first and second surfaces of the semiconductor stack, as an optical image corresponding to the arrangement of multiple regions with different refractive indices. The optical images emitted from each of the multiple phase modulation regions are phase-synchronous with each other. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-131320 [Overview of the project] [Problems that the invention aims to solve]

[0004] When the present inventors fabricated a semiconductor light-emitting element described in Patent Document 1, they found that a spot-like light of unknown origin (hereinafter referred to as "stray light" in this disclosure), unrelated to the intended light image, was emitted from the semiconductor light-emitting element along with the intended light image. To output only the intended light image from the semiconductor light-emitting element, it is desirable to reduce such stray light. The object of this disclosure is to provide a semiconductor light-emitting element that can reduce stray light. [Means for solving the problem]

[0005] [1] A semiconductor light-emitting element according to one aspect of the present disclosure comprises a semiconductor stack, a first electrode section, and a second electrode section. The semiconductor stack has a stacked structure between a first surface and a second surface. The stacked structure includes an active layer and a phase modulation layer. The phase modulation layer has a plurality of phase modulation regions. The plurality of phase modulation regions are aligned along a virtual plane perpendicular to the thickness direction of the phase modulation layer and are optically coupled to one another. Each of the plurality of phase modulation regions includes a basic region and a plurality of different refractive index regions. The basic region has a first refractive index. The plurality of different refractive index regions are provided within the basic region, have a second refractive index different from the first refractive index, and are distributed two-dimensionally along the virtual plane. The first electrode section faces the first surface of the semiconductor stack. The second electrode section faces the second surface of the semiconductor stack. One or both of the first electrode section and the second electrode section include a plurality of electrodes that overlap with the plurality of phase modulation regions when viewed from the stacking direction of the semiconductor stack. The plurality of electrodes are electrically isolated from one another. Light emitted from the active layer resonates along a virtual plane in each of the multiple phase modulation regions of the phase modulation layer. The resonant light is irradiated from each of the multiple phase modulation regions to an irradiation region located in a direction intersecting both the first and second surfaces of the semiconductor stack, via the second surface. The semiconductor light-emitting element has a reflection reduction structure configured to reduce reflection of light emitted from each phase modulation region at the first electrode portion.

[0006] Through trial and error, the inventors of this invention discovered that when the emission wavelength of the active layer is 940 nm, providing an InGaAs layer of a certain thickness (e.g., 500 nm) between the first electrode, which is located on the opposite side of the light emission surface, and the GaAs contact layer significantly reduces stray light. InGaAs has relatively high light absorption at a wavelength of 940 nm. In addition, because InGaAs is lattice mismatched with GaAs, the surface of the InGaAs layer becomes rough. From these findings, it is thought that the absorption and scattering of light emitted from the phase modulation layer on the opposite side of the light emission surface before reaching the first electrode reduces the reflection of light at the first electrode, which leads to the reduction of stray light. In other words, it is thought that the reflection of light at the first electrode is the cause of stray light. Furthermore, stray light does not occur in semiconductor light-emitting devices in which the phase modulation layer is not divided into multiple phase modulation regions. Therefore, it is presumed that stray light is caused by light emitted from a certain phase modulation region and reflected by the first electrode portion mixing with light output from an adjacent phase modulation region. According to the semiconductor light-emitting element described in [1] above, stray light can be effectively reduced by providing a reflection reduction structure configured to reduce the reflection of light emitted from each phase modulation region at the first electrode portion.

[0007] [2] In the semiconductor light-emitting element described in [1] above, the reflection reduction structure may include a structure that scatters light directed from each phase modulation region toward the first electrode portion. The scattering structure is provided between both the active layer and the phase modulation layer and the first electrode portion, and may overlap with a plurality of phase modulation regions when viewed from the stacking direction. By scattering light directed from each phase modulation region toward the first electrode portion, reflection at the first electrode portion can be reduced. Therefore, stray light can be effectively reduced.

[0008] [3] In the semiconductor light-emitting element described in [2] above, the scattering structure may include an uneven structure formed at the interface of two adjacent layers within the semiconductor stack or on the first surface. For example, such a structure can scatter light from each phase modulation region toward the first electrode portion.

[0009] [4] In the semiconductor light-emitting element described in [3] above, the semiconductor stack may include a cladding layer provided on the active layer and the phase modulation layer, and a contact layer provided on the cladding layer and adjacent to the cladding layer. The uneven structure may be formed at the interface between the cladding layer and the contact layer. In this case, light directed from each phase modulation region toward the first electrode portion can be effectively scattered.

[0010] [5] In the semiconductor light-emitting element described in [3] or [4] above, the uneven structure may be caused by lattice mismatch within the semiconductor stack. In this case, the uneven structure can be easily formed.

[0011] [6] In the semiconductor light-emitting devices described in [1] to [5] above, the reflection reduction structure may include a structure provided between both the active layer and the phase modulation layer and the first electrode portion, which overlaps with a plurality of phase modulation regions when viewed from the stacking direction, and which absorbs light directed from each phase modulation region toward the first electrode portion. By absorbing light directed from each phase modulation region toward the first electrode portion, reflection at the first electrode portion can be reduced. Therefore, stray light can be effectively reduced.

[0012] [7] In the semiconductor light-emitting element described in [6] above, the absorbing structure may include a light-absorbing layer provided in the semiconductor stack. For example, such a structure can absorb light from each phase modulation region toward the first electrode portion.

[0013] [8] In the semiconductor light-emitting element described in [7] above, the semiconductor stack may include a cladding layer provided on the active layer and the phase modulation layer, and a contact layer provided on the cladding layer. The light-absorbing layer may be provided between the cladding layer and the contact layer, or between the contact layer and the first electrode portion. In this case, light directed from each phase modulation region toward the first electrode portion can be effectively absorbed.

[0014] [9] In the semiconductor light-emitting element described in [7] above, the semiconductor stacking may include a cladding layer provided on the active layer and the phase modulation layer, and a contact layer provided on the cladding layer as a light-absorbing layer. In this case, light directed from each phase modulation region toward the first electrode portion can be effectively absorbed.

[0015]

[10] In the semiconductor light-emitting devices described in [7] to [9] above, the light-absorbing layer may have a light absorption rate of 50% or more at the emission wavelength of the active layer. In this case, light from each phase modulation region toward the first electrode can be effectively absorbed.

[0016]

[11] In the semiconductor light-emitting devices described in [1] to

[10] above, the reflection reduction structure may include a structure that transmits light from each phase modulation region at the first electrode. By transmitting light from each phase modulation region toward the first electrode at the first electrode, the reflection of light can be reduced. Therefore, stray light can be effectively reduced.

[0017]

[12] In the semiconductor light-emitting element described in

[11] above, the first electrode portion may have a light transmittance of 50% or more at the emission wavelength of the active layer. In this case, light directed from each phase modulation region toward the first electrode portion can be effectively transmitted through the first electrode portion. [Effects of the Invention]

[0018] According to this disclosure, it is possible to provide a semiconductor light-emitting element that can reduce stray light. [Brief explanation of the drawing]

[0019] [Figure 1] Figure 1 is a cross-sectional view showing the stacked structure of a semiconductor light-emitting element. [Figure 2] Figure 2 is a plan view of the phase modulation layer (viewed from the thickness direction). [Figure 3] Figure 3 is a plan view showing an enlarged portion of the phase modulation region. [Figure 4] Figure 4 is a magnified view of a single unit constituent region. [Figure 5] Figure 5 is a diagram illustrating the coordinate transformation from spherical coordinates to coordinates in the XYZ Cartesian coordinate system. [Figure 6] Figure 6 is a plan view showing an enlarged portion of the connection area. [Figure 7] Figure 7 schematically shows the planar shapes of the first electrode section and the second electrode section, as well as the configuration for supplying current to the first electrode section and the second electrode section. [Figure 8] Figure 8 shows the electromagnetic field distribution in the phase modulation region. Part 8(a) of Figure 8 shows the electromagnetic field distribution in the resonant mode with symmetry A1 at point M1. Part 8(b) of Figure 8 shows the electromagnetic field distribution in the resonant mode with symmetry B2 at point M1. [Figure 9] Figure 9 shows the electromagnetic field distribution for a comparative example. Part 9(a) shows the electromagnetic field distribution in the resonant mode with symmetry A1 at point M1. Part 9(b) shows the electromagnetic field distribution in the resonant mode with symmetry B2 at point M1. [Figure 10] Figure 10 is a conceptual diagram illustrating examples of multiple optical images output from multiple phase modulation regions. [Figure 11] Figure 11 is a conceptual diagram illustrating another example of multiple optical images output from multiple phase modulation regions. [Figure 12] Figure 12 is a conceptual diagram illustrating yet another example of multiple optical images output from multiple phase modulation regions. [Figure 13] Figure 13 is a conceptual diagram illustrating the first design method. [Figure 14] Figure 14 shows a phase modulation layer having a total of four phase modulation regions, with two columns in the X direction and two rows in the Y direction. [Figure 15] Figure 15 shows a phase modulation layer in which the two phase modulation regions in the first row have phase distribution pattern B, and the two phase modulation regions in the second row have phase distribution pattern A. [Figure 16] Figure 16 is a conceptual diagram illustrating the design methods for phase distribution patterns A and B. [Figure 17]Figure 17 shows a phase modulation layer having a total of m × n phase modulation regions, with m columns in the X direction and n rows in the Y direction. [Figure 18] Figure 18 is a conceptual diagram illustrating a method for designing m × n phase distribution patterns. [Figure 19] Figure 19 is a conceptual diagram illustrating the second design method. [Figure 20] Figure 20 is a conceptual diagram illustrating the design methods for phase distribution patterns A and B. [Figure 21] Figure 21 is a conceptual diagram illustrating a method for designing m × n phase distribution patterns. [Figure 22] Figure 22(a) shows a far-field image observed in the fabricated semiconductor light-emitting device. [Figure 23] Figure 23 shows an image obtained by observing the area near the contact layer of a semiconductor light-emitting element using a Nomarski microscope. [Figure 24] Figure 24 is a cross-sectional view showing the configuration of a semiconductor light-emitting element disclosed in Patent Document 1, which does not have a reflection reduction structure. [Figure 25] Figure 25 is a diagram illustrating the effects obtained by the semiconductor light-emitting element according to the first embodiment. [Figure 26] Figure 26 is a cross-sectional view showing the stacked structure of a semiconductor light-emitting element according to the first modified example. [Figure 27] Figure 27 is a cross-sectional view showing the stacked structure of a semiconductor light-emitting element according to a second modified example. [Figure 28] Figure 28 is a plan view of the cladding layer. [Figure 29] Figure 29 is a cross-sectional view showing the configuration of a semiconductor light-emitting element according to a third modified example. [Figure 30] Figure 30 is a plan view showing the phase modulation layer. [Figure 31] Figure 31 is a plan view showing a partially enlarged view of the phase shift region and the surrounding connection region. [Figure 32] Figure 32 is a diagram showing an enlarged view of one unit constituent region. [Figure 33]Figure 33 is a cross-sectional view showing the stacked structure of a semiconductor light-emitting element according to the second embodiment. [Figure 34] Figure 34 is a cross-sectional view showing the stacked structure of a semiconductor light-emitting element according to the fifth modified example. [Figure 35] Figure 35 is a cross-sectional view showing the stacked structure of a semiconductor light-emitting element according to the sixth modified example. [Figure 36] Figure 36 is a cross-sectional view showing the stacked structure of a semiconductor light-emitting element according to the third embodiment. [Modes for carrying out the invention]

[0020] Specific examples of the semiconductor light-emitting devices of this disclosure will be described below with reference to the drawings. However, the present invention is not limited to these examples, and is intended to include all modifications within the meaning and scope of the claims, as defined by the claims. In the following description, the same elements in the drawings are denoted by the same reference numerals, and redundant descriptions are omitted.

[0021] [First Embodiment] Figure 1 is a cross-sectional view showing the stacked structure of the semiconductor light-emitting element 1A of this embodiment. In Figure 1, an XYZ Cartesian coordinate system is defined with the axis extending in the thickness direction of the semiconductor light-emitting element 1A as the Z-axis. The semiconductor light-emitting element 1A is a laser light source that forms a standing wave in the XY plane direction and outputs a phase-controlled plane wave in a direction intersecting its thickness direction. The semiconductor light-emitting element 1A is an S-iPM laser and can output an optical image of any shape in a direction perpendicular to the main surface 10a of the semiconductor substrate 10, i.e., the Z direction, or a direction inclined with respect to the Z direction, or a direction including both.

[0022] The semiconductor light-emitting element 1A comprises a semiconductor substrate 10. The semiconductor substrate 10 has a main surface 10a and a back surface 10b. The normal direction of the main surface 10a and the back surface 10b, and the thickness direction of the semiconductor substrate 10 are aligned with the Z direction. The semiconductor substrate 10 is composed of a compound semiconductor such as a GaAs-based semiconductor, an InP-based semiconductor, or a nitride-based semiconductor.

[0023] The semiconductor light-emitting element 1A further comprises a semiconductor stack 20. The semiconductor stack 20 is provided on the main surface 10a of the semiconductor substrate 10. The stacking direction of the semiconductor stack 20 is along the Z direction. The semiconductor stack 20 has a stacked structure including a cladding layer 11, an active layer 12, a cladding layer 13, a contact layer 14, and a phase modulation layer 15 between the first surface 20a and the second surface 20b. The second surface 20b of the semiconductor stack 20 faces the main surface 10a of the semiconductor substrate 10. In the illustrated example, the cladding layer 11 is provided on the main surface 10a of the semiconductor substrate 10, the active layer 12 is provided on the cladding layer 11, the phase modulation layer 15 is provided on the active layer 12, the cladding layer 13 is provided on the phase modulation layer 15, and the contact layer 14 is provided on the cladding layer 13. Specifically, the cladding layer 11 is provided between the active layer 12 and the second surface 20b, and the cladding layer 13 is provided between the active layer 12 and the first surface 20a, with the cladding layers 11 and 13 sandwiching the active layer 12 and the phase modulation layer 15. In the illustrated example, the phase modulation layer 15 is provided between the active layer 12 and the cladding layer 13, but the phase modulation layer 15 may also be provided between the cladding layer 11 and the active layer 12. Optical guide layers may be provided between the active layer 12 and the cladding layer 13, and between the active layer 12 and the cladding layer 11, or both, as needed. The optical guide layer may include a carrier barrier layer for efficiently confining carriers in the active layer 12.

[0024] The cladding layer 11, active layer 12, cladding layer 13, and contact layer 14 are composed of compound semiconductors such as GaAs-based semiconductors, InP-based semiconductors, or nitride-based semiconductors. The active layer 12 has, for example, a multiple quantum well structure. The energy band gaps of cladding layer 11 and cladding layer 13 are larger than the energy band gap of active layer 12. The thickness directions of cladding layer 11, active layer 12, cladding layer 13, and contact layer 14 coincide with the Z-axis direction.

[0025] The phase modulation layer 15 is optically coupled to the active layer 12. The thickness direction of the phase modulation layer 15 coincides with the Z-axis direction. Figure 2 is a plan view (viewed from the thickness direction) of the phase modulation layer 15. As shown in Figures 1 and 2, the phase modulation layer 15 has a plurality of phase modulation regions 151 and connection regions 152. The planar shape of the connection regions 152 viewed from the stacking direction of the semiconductor stack 20 is, for example, a grid. Each of the plurality of phase modulation regions 151 is provided in each of the plurality of openings 152a of the grid-shaped connection regions 152.

[0026] The planar shape of each of the multiple phase modulation regions 151 is, for example, a square or a rectangle. The multiple phase modulation regions 151 are arranged two-dimensionally along a virtual plane P perpendicular to the thickness direction of the phase modulation layer 15 (in other words, parallel to the XY plane) and are optically coupled to one another. In the illustrated example, the multiple phase modulation regions 151 are arranged along the X and Y directions. Although the multiple phase modulation regions 151 are arranged two-dimensionally in the illustrated example, they may also be arranged one-dimensionally. In the illustrated example, the multiple phase modulation regions 151 are spaced apart from each other. The connecting region 152 includes a portion 152b provided between adjacent phase modulation regions 151 and an outer frame-shaped portion 152c that encloses the multiple phase modulation regions 151 together.

[0027] As shown in Figure 1, each of the multiple phase modulation regions 151 is composed of a basic region 15a and multiple regions with different refractive indices 15b. Similarly, the connecting region 152 is also composed of a basic region 15a and multiple regions with different refractive indices 15b. The basic region 15a consists of a first refractive index medium. The basic region 15a is composed of a compound semiconductor such as a GaAs-based semiconductor, an InP-based semiconductor, or a nitride-based semiconductor. The multiple regions with different refractive indices 15b consist of a second refractive index medium with a different refractive index from the first refractive index medium and exist within the basic region 15a. The regions with different refractive indices 15b are, for example, voids. The regions with different refractive indices 15b are covered by a cap region 15c provided on the basic region 15a. The cap region 15c constitutes part of the phase modulation layer 15 and is made of, for example, the same material as the basic region 15a.

[0028] Multiple regions with different refractive indices 15b are distributed two-dimensionally along a virtual plane P. In each phase modulation region 151, the multiple regions with different refractive indices 15b contain a lattice-like, approximately periodic structure. If the equivalent refractive index of the mode is n and the lattice spacing is a, the wavelength λ0 selected by each phase modulation region 151 is expressed as λ0 = (√2)a × n, for example, in the case of M1 point oscillation. This wavelength λ0 is included within the emission wavelength range of the active layer 12. Each phase modulation region 151 can select a band edge wavelength near wavelength λ0 from the emission wavelength of the active layer 12 and output it to the outside. Light incident from the active layer 12 into each phase modulation region 151 forms a predetermined mode within each phase modulation region 151 according to the arrangement of the regions with different refractive indices 15b, and is output as laser light L from the back surface 10b of the semiconductor substrate 10 to the outside of the semiconductor light-emitting element 1A via the second surface 20b.

[0029] Figure 3 is a plan view showing an enlarged portion of the phase modulation region 151. Although Figure 3 shows only one phase modulation region 151, the configuration of other phase modulation regions 151 is similar. As mentioned above, the phase modulation region 151 includes a basic region 15a and multiple regions with different refractive indices 15b. In Figure 3, a virtual square grid is set up along a virtual plane P for the phase modulation region 151. One side of the square grid is parallel to the X axis, and the other side is parallel to the Y axis. The square-shaped unit constituent regions R, centered on the grid points O of the square grid, are arranged two-dimensionally across multiple columns along the X axis and multiple rows along the Y axis. The XY coordinates of each unit constituent region R are defined by the centroid position of each unit constituent region R. These centroid positions coincide with the grid points O of the virtual square grid. For example, one region with different refractive indices 15b is provided within each unit constituent region R. The planar shape of the region with different refractive indices 15b is, for example, circular. The lattice point O may be located outside the region of different refractive indices 15b, or it may be located inside the region of different refractive indices 15b.

[0030] Figure 4 is a magnified view of one unit constituent region R. As shown in the figure, each of the different refractive index regions 15b has a centroid G. The centroid G of the different refractive index regions 15b is located on a line D set for each lattice point O. Line D is a line that passes through the lattice point O corresponding to each unit constituent region R and is inclined with respect to each side of the square lattice. In other words, line D is a line that is inclined with respect to both the X axis and the Y axis. The inclination angle of line D with respect to one side of the square lattice, in other words, the X axis, is β.

[0031] The inclination angle β is the same for all lines D within the phase modulation region 151. Furthermore, the inclination angle β is the same across multiple phase modulation regions 151. The inclination angle β satisfies 0° < β < 90°, in one example β = 45°. Alternatively, the inclination angle β satisfies 180° < β < 270°, in one example β = 225°. When the inclination angle β satisfies 0° < β < 90° or 180° < β < 270°, the line D extends from the first to the third quadrant of the coordinate plane defined by the X and Y axes. The inclination angle β satisfies 90° < β < 180°, in one example β = 135°. Alternatively, the inclination angle β satisfies 270° < β < 360°, in one example β = 315°. If the inclination angle β satisfies 90° < β < 180° or 270° < β < 360°, the line D extends from the second to the fourth quadrant of the coordinate plane defined by the X and Y axes. Thus, the inclination angle β is an angle other than 0°, 90°, 180°, and 270°.

[0032] Here, let r(x,y) be the distance between the grid point O and the centroid G. x is the position of the x-th grid point on the X-axis, and y is the position of the y-th grid point on the Y-axis. When the distance r(x,y) is a positive value, the centroid G is located in the first or second quadrant. When the distance r(x,y) is a negative value, the centroid G is located in the third or fourth quadrant. When the distance r(x,y) is 0, the grid point O and the centroid G coincide with each other. Preferred inclination angles are 45°, 135°, 225°, and 315°. In the case of these inclination angles, only two of the four wave vectors that form the standing wave at point M, for example, the in-plane wave vectors (±π / a, ±π / a), are phase-modulated, while the other two are not phase-modulated. Therefore, a stable standing wave can be formed.

[0033] The distance r(x,y) is set individually for each different refractive index region 15b according to the phase distribution φ(x,y) corresponding to the optical image to be output from each phase modulation region 151. That is, if the phase φ(x,y) at a certain coordinate (x,y) is φ0, the distance r(x,y) is set to 0. If the phase φ(x,y) is π+φ0, the distance r(x,y) is set to the maximum value R0. If the phase φ(x,y) is -π+φ0, the distance r(x,y) is set to the minimum value -R0. For intermediate phases φ(x,y), the distance r(x,y) is set such that r(x,y)={φ(x,y)-φ0}×R0 / π. If the grid spacing of a virtual square grid is a, the maximum value R0 of r(x,y) will be within the range of, for example, the following equation (1).

number

[0034] By determining the distribution of the distance r(x, y) of each of the plurality of phase modulation regions 151 in the anisotropic refractive index region 15b, a desired optical image can be output from each of the plurality of phase modulation regions 151. Each phase modulation region 151 is configured to satisfy the following conditions.

[0035] As a first prerequisite, a virtual square lattice composed of M1×N1 unit constituent regions R having a square shape is set on the XY plane. M1 and N1 are integers of 1 or more.

[0036] As shown in FIG. 5, the radial length r, the inclination angle θ from the Z axis tilt and the rotation angle θ from the X axis specified on the XY plane rot define spherical coordinates (r, θ rot , θ tilt ). As a second prerequisite, it is assumed that the coordinates (ξ, η, ζ) in the XYZ orthogonal coordinate system satisfy the relationships shown in the following equations (2) to (4) with respect to the spherical coordinates (r, θ rot , θ tilt ). FIG. 5 is a diagram for explaining the coordinate conversion from the spherical coordinates (r, θ rot , θ tilt ) to the coordinates (ξ, η, ζ) in the XYZ orthogonal coordinate system. The coordinates (ξ, η, ζ) represent a designed optical image on a predetermined plane set in the XYZ orthogonal coordinate system in real space.

Equation

Equation

Equation

[0037] Let the light emitted from each phase modulation region 151 be a set of bright spots directed in the directions defined by the angles θ tilt and θ rot . At this time, the angles θ tilt and θ rotThese shall be converted to coordinate values ​​kx and ky. The coordinate value kx is the normalized wavenumber defined by the following equation (5), and corresponds to K on the X axis. x These are coordinate values ​​on the axis. The coordinate value ky is a normalized wavenumber defined by the following equation (6), and corresponds to the Y axis and K x K perpendicular to the axis y These are coordinate values ​​on the axis. The normalized wavenumber refers to the wavenumber normalized by setting the wavenumber 2π / a, which corresponds to the grid spacing of a hypothetical square grid, to 1.0. In this case, K x Axis and K y In the wavenumber space defined by the axis, a specific wavenumber range containing a beam pattern corresponding to an optical image is composed of M2 × N2 image regions FR, each of which is square in shape. M2 and N2 are integers greater than or equal to 1. The integer M2 does not need to be the same as the integer M1. The integer N2 does not need to be the same as the integer N1. Equations (5) and (6) are disclosed, for example, in Non-Patent Document 1.

number

number

[0038] In wavenumber space, the image region FR(kx,ky) is K x Axial coordinate components kx and K yThe coordinate components kx and y are specified by the coordinate components ky in the axial direction. The coordinate component kx is an integer between 0 and M2-1, and the coordinate component ky is an integer between 0 and N2-1, and the unit constituent region R(x,y) on the XY plane is specified by the coordinate component x in the X direction and the coordinate component y in the Y direction. The coordinate component x is an integer between 0 and M1-1, and the coordinate component y is an integer between 0 and N N1-1, and the coordinate component y is an integer between N1-1, and the coordinate component y is an integer between N1-1, and the coordinate component y is an integer between N1-1, and the coordinate component y is an integer between N1-1, and the coordinate component y is an integer between N1-1, and the coordinate component y is an integer between N1-1, and the coordinate component y is an integer between N1-1, and the coordinate component y is an integer between N1-1, and the coordinate component y is an integer between N1- The s-axis and t-axis are parallel to the x-axis and y-axis, respectively, and are orthogonal to each other at the lattice point O(x,y) which is the center of the unit constituent region R(x,y).

number

number

[0039] Under the first to fourth preconditions described above, each phase modulation region 151 is configured to satisfy the following conditions. That is, the distance r(x,y) from the lattice point O(x,y) to the centroid G of the corresponding differential refractive index region 15b satisfies the following relationship, and the corresponding differential refractive index region 15b is arranged within the unit configuration region R(x,y). r(x,y) = C × (φ(x,y) - φ0) C: Proportionality constant, for example, R0 / π φ0: Any constant, for example, 0 To obtain a desired optical image, it is advisable to perform an inverse Fourier transform on the optical image and assign a distribution of distances r(x,y) corresponding to the phase φ(x,y) of its complex amplitude to multiple regions 15b with different refractive indices. The phase φ(x,y) and the distance r(x,y) may be proportional to each other.

[0040] Figure 6 is a plan view showing an enlarged portion of the connection region 152. Although only a portion of the connection region 152 is shown in Figure 6, the configuration of the other parts of the connection region 152 is similar. As mentioned above, the connection region 152 also includes the basic region 15a and multiple regions with different refractive indices 15b. In the connection region 152, a virtual square lattice is set up similarly to that in Figure 3. One side of the square lattice is parallel to the X axis, and the other side is parallel to the Y axis. The lattice constant a of the square lattice is equal to the lattice constant a of the phase modulation region 151 and the square lattice. In the connection region 152, the centroid G of the multiple regions with different refractive indices 15b is located at the lattice points of the square lattice. In other words, the positions of the centroid G of the multiple regions with different refractive indices 15b coincide with the positions of the lattice points of the square lattice. Therefore, in the connection region 152, the multiple regions with different refractive indices 15b are arranged periodically along the X and Y axes.

[0041] Refer to Figure 1 again. The semiconductor light-emitting element 1A further comprises an electrode portion 16 (first electrode portion) and an electrode portion 17 (second electrode portion). The electrode portion 16 is provided facing the first surface 20a of the semiconductor stack 20, and in the illustrated example, the electrode portion 16 is provided on the first surface 20a, i.e., on the contact layer 14. The electrode portion 16 makes ohmic contact with the contact layer 14. The electrode portion 17 is provided facing the second surface 20b of the semiconductor stack 20, and in the illustrated example, the electrode portion 17 is provided on the back surface 10b of the semiconductor substrate 10. The electrode portion 17 makes ohmic contact with the semiconductor substrate 10. Typical shapes include the electrode 161 (described later) of the electrode portion 16 being a square shape with a side length in the range of 50 μm to 500 μm, or a perfect circle shape with a diameter in the range of 50 μm to 500 μm. Furthermore, the electrode portion 17 is an open electrode with an opening that has a square shape, where the length of one side is in the range of 50 μm to 500 μm.

[0042] Figure 7 schematically shows the planar shapes of the electrode sections 16 and 17, and the configuration for supplying current to the electrode sections 16 and 17. As shown in Figure 7, the electrode section 17 has a plurality of openings 17a. Each opening 17a corresponds one-to-one with each phase modulation region 151. Viewed from the thickness direction of the semiconductor stack 20, the openings 17a overlap with the corresponding phase modulation region 151. The planar shape of each opening 17a is, for example, a square or rectangle. The electrode section 16 includes a plurality of electrodes 161. The plurality of electrodes 161 are arranged with gaps between them and are electrically isolated from each other. Note that the electrodes being electrically isolated from each other means that there are no other paths through which they are electrically connected, except for the path through the semiconductor stack 20. Each electrode 161 corresponds one-to-one with each phase modulation region 151. Viewed from the thickness direction of the semiconductor stack 20, the electrodes 161 overlap with the corresponding phase modulation region 151. The planar shape of each electrode 161 is, for example, a square or a rectangle.

[0043] Each of the multiple electrodes 161 is individually electrically connected to the drive circuit 31 via each of the multiple wirings 33. The electrode section 17 is also electrically connected to the drive circuit 31 via wiring 34. The drive circuit 31 is electrically connected to the power supply circuit 32 via wiring 35. The drive circuit 31 receives power from the power supply circuit 32 and supplies drive current between the multiple electrodes 161 and the electrode section 17. The drive circuit 31 can freely change the magnitude of the drive current for each electrode 161. The magnitude of the drive current to each electrode 161 is set independently for each electrode 161.

[0044] Refer to Figure 1 again. The parts of the contact layer 14 other than those overlapping with each electrode 161 are removed by etching in order to limit the current range. Thus, the contact layer 14 is divided into multiple parts, each corresponding to one of the multiple electrodes 161. The gaps between the multiple parts of the contact layer 14 are filled with a protective film 18. This protects the surface of the semiconductor laminate 20 exposed from the electrode portion 16. The protective film 18 is made of an inorganic insulator such as silicon nitride (e.g., SiN) or silicon oxide (e.g., SiO2). Note that the parts of the contact layer 14 other than those overlapping with each electrode 161 may remain without being removed. In that case, the protective film 18 is provided on the contact layer 14 in the gaps between the multiple electrodes 161.

[0045] Of the back surface 10b of the semiconductor substrate 10, all areas except the region where the electrode portion 17 is provided are covered with an anti-reflective film 19, including within the opening 17a. The anti-reflective film 19 in areas other than the opening 17a may be removed. The anti-reflective film 19 consists of a single-layer or multilayer film of a dielectric material, such as silicon nitride (e.g., SiN) or silicon oxide (e.g., SiO2). As the dielectric multilayer film, for example, a film can be used in which two or more dielectric layers selected from the group of dielectric layers consisting of 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 oxide (CeO2), indium oxide (In2O3), and zirconium oxide (ZrO2) are laminated. Dielectric multilayer films are formed, for example, by stacking multiple films, each having an optical film thickness of λ / 4 for light of wavelength λ.

[0046] In this embodiment, the electrode portion 16 facing the first surface 20a includes a plurality of electrodes 161. However, instead of this configuration, or in conjunction with this configuration, the electrode portion 17 facing the second surface 20b may also include a plurality of electrodes. In this case, similar to the plurality of electrodes 161, the plurality of electrodes of the electrode portion 17 are also arranged with gaps between them and are electrically isolated from each other. Each electrode of the electrode portion 17 corresponds one-to-one with each phase modulation region 151. When viewed from the thickness direction of the semiconductor stack 20, each electrode of the electrode portion 17 overlaps with the corresponding phase modulation region 151. The planar shape of each electrode of the electrode portion 17 is, for example, a rectangular frame shape including an opening 17a. Each of the plurality of electrodes of the electrode portion 17 is individually electrically connected to the drive circuit 31 via each of the plurality of wires. The drive circuit 31 freely changes the magnitude of the drive current for each electrode of the electrode portion 17.

[0047] The semiconductor light-emitting element 1A has a plurality of reflection reduction structures 41. Each reflection reduction structure 41 is configured to reduce the reflection of light emitted from each phase modulation region 151 at the electrode portion 16. The reflection reduction structure 41 in this embodiment includes a structure that scatters light directed from the phase modulation region 151 toward the electrode portion 16. The scattering structure is provided between both the active layer 12 and the phase modulation layer 15 and the electrode portion 16, and overlaps with the plurality of phase modulation regions 151 when viewed from the stacking direction of the semiconductor stack 20. For example, the scattering structure includes an uneven structure formed on the surface of the contact layer 14, i.e., the first surface 20a. The uneven structure is caused, for example, by lattice mismatch in the semiconductor stack 20, particularly in the layers above both the active layer 12 and the phase modulation layer 15. Alternatively, the uneven structure is formed, for example, by roughening the first surface 20a with sandpaper or the like. In that case, the surface roughness (RMS value) of the first surface 20a is, for example, in the range of 30 nm to 50 nm.

[0048] In the semiconductor light-emitting element 1A, when a drive current is supplied between the electrode 161 and the electrode portion 17, electron-hole recombination occurs in the portion of the active layer 12 located directly beneath the electrode 161, and light is emitted from that portion of the active layer 12. At this time, the electrons and holes contributing to light emission, as well as the light emitted from the active layer 12, are efficiently confined between the cladding layer 11 and the cladding layer 13.

[0049] Light emitted from the portion of the active layer 12 is incident on the phase modulation region 151 opposite to that portion. The light then resonates along the virtual plane P in the phase modulation region 151, forming a predetermined mode corresponding to the arrangement of the multiple regions with different refractive indices 15b. A portion of the laser light L emitted from the phase modulation region 151 is directly output to the outside of the semiconductor light-emitting element 1A through the aperture 17a from the back surface 10b. At this time, the signal light contained in the laser light L is emitted in a direction that intersects both the first surface 20a and the second surface 20b of the semiconductor stack 20. In other words, the signal light contained in the laser light L is emitted in any direction including a direction perpendicular to the back surface 10b and a direction inclined with respect to the direction perpendicular to the back surface 10b. The light emitted from the semiconductor light-emitting element 1A is composed of signal light. The signal light is mainly the first-order diffracted light or the -1st-order diffracted light of the laser light, or both. Hereinafter, the first-order diffracted light will be referred to as the first-order light, and the -1st-order diffracted light will be referred to as the -1st-order light. The remainder of the laser light L output from the phase modulation region 151 is scattered by the reflection reduction structure 41.

[0050] The laser light L emitted from each of the multiple phase modulation regions 151 is projected onto a common irradiation region (far field) located in a direction intersecting both the first surface 20a and the second surface 20b of the semiconductor stack 20, forming an optical image corresponding to the arrangement of the multiple different refractive index regions 15b. The multiple different refractive index regions 15b included in at least two of the multiple phase modulation regions 151 have a different arrangement for each phase modulation region 151. Therefore, the multiple optical images emitted from each of the multiple phase modulation regions 151 interfere with each other to form the final optical image.

[0051] To obtain a final optical image by interfering with each other with multiple optical images output from multiple phase modulation regions 151, these optical images are phase-synchronized with each other. In this embodiment, to ensure that these optical images are phase-synchronized, a connection region 152 is provided between adjacent phase modulation regions 151. Since the resonance modes of adjacent phase modulation regions 151 are shared via the connection region 152, the phase of the laser light L resonating in each phase modulation region 151 can be synchronized among the multiple phase modulation regions 151. Alternatively, the connection region 152 may be eliminated, and adjacent phase modulation regions 151 may be placed next to each other. Even in such a case, the phase of the laser light L resonating in each phase modulation region 151 can still be synchronized among the multiple phase modulation regions 151. In order to phase-synchronize multiple optical images, phase synchronization must also be considered when designing the phase distribution φ(x,y) of each phase modulation region 151. The design of the phase distribution φ(x,y) considering phase synchronization will be described later.

[0052] Furthermore, in order to obtain a desired optical image by interfering the optical images output from each of the multiple phase modulation regions 151 with each other, it is desirable that the polarization directions of these optical images be aligned. In this embodiment, the centroid G of the different refractive index regions 15b is located on a straight line D set for each grid point O. The inclination angle β of the straight line D is the same for all grid points O within the phase modulation region 151, and is also the same for multiple phase modulation regions 151.

[0053] Here, Figure 8 shows the electromagnetic field distribution in the phase modulation region 151. Part 8(a) of Figure 8 shows the electromagnetic field distribution in the resonant mode with symmetry A1 at point M1. Part 8(b) of Figure 8 shows the electromagnetic field distribution in the resonant mode with symmetry B2 at point M1. In Figure 8, the arrows represent the magnitude and direction of the electric field, and the intensity of the color represents the magnitude of the magnetic field. In this embodiment, the centroid G of the different refractive index regions 15b is arranged on a straight line D. The figure schematically shows the change in the arrangement of the central different refractive index regions 15b. In that case, it is expected that the polarization directions will be aligned in any electromagnetic field distribution, regardless of the distance between the centroid G of the different refractive index regions 15b and the lattice point O, in other words, regardless of the phase value realized by each different refractive index region 15b.

[0054] On the other hand, Figure 9 shows the electromagnetic field distribution when, as a comparative example, the centroid G of the different refractive index region 15b is located at a constant distance from the grid point O, and the azimuthal angle (rotation angle) of the vector connecting the grid point O to the centroid G around the grid point O is set for each different refractive index region 15b according to the phase distribution φ(x,y). In this example, part 9(a) shows the electromagnetic field distribution in the resonant mode of symmetry A1 at point M1. Part 9(b) shows the electromagnetic field distribution in the resonant mode of symmetry B2 at point M1. In Figure 9 as well, the arrows represent the magnitude and direction of the electric field, and the intensity of the color represents the magnitude of the magnetic field. In this comparative example, in both electromagnetic field distributions, the polarization direction changes according to the rotation angle of the different refractive index region 15b around the grid point O. Therefore, it is almost impossible to expect the polarization directions to be aligned. For these reasons, it is desirable to have a configuration like that of this embodiment, where the centroid G of the different refractive index region 15b is located on a straight line D, and the distance between the centroid G and the grid point O changes according to the phase.

[0055] As described above, the semiconductor light-emitting element 1A of this embodiment illuminates a common illumination area with multiple optical images output from multiple phase modulation regions 151. A single final optical image (hologram) is formed by superimposing and interfering these multiple optical images. Figure 10 conceptually shows an example of multiple optical images output from multiple phase modulation regions 151. Figure 10 shows a total of 64 optical images LA, arranged in 8 columns in the X direction and 8 rows in the Y direction, with darker images indicating lower light intensity and fainter images indicating higher light intensity. These are optical images output from 64 phase modulation regions 151, arranged in 8 columns in the X direction and 8 rows in the Y direction. In this example, the light intensity distribution of the optical images LA output from each of the multiple phase modulation regions 151 includes a sinusoidal distribution. In this sinusoidal distribution, the periods in two mutually orthogonal directions (X and Y directions) differ for each phase modulation region 151. Such optical images LA can be used, for example, as a basis image for a discrete cosine transform (DCT). In other words, the final optical image can be realized by performing a discrete cosine transform on the light intensity distribution of the target final optical image and outputting the resulting multiple base images from multiple phase modulation regions 151. Furthermore, by changing the magnitude of the driving current of multiple electrodes 161 corresponding to each of the multiple phase modulation regions 151, the contribution of each base image to the final optical image can be individually adjusted, thereby presenting a time-varying dynamic optical image.

[0056] Figure 11 conceptually illustrates another example of multiple optical images output from multiple phase modulation regions 151. This example shows multiple optical images LA used as basis images for a discrete wavelet transform (DWT). As in this example, the final optical image can also be realized by performing a discrete wavelet transform on the optical intensity distribution of the final optical image and outputting the resulting basis images from multiple phase modulation regions 151. Furthermore, by changing the magnitude of the drive current of multiple electrodes 161 corresponding to each of the multiple phase modulation regions 151, the contribution of each basis image to the final optical image can be individually adjusted to present a time-varying dynamic optical image.

[0057] Furthermore, the method is not limited to discrete cosine transform and discrete wavelet transform; for example, a base image may be learned from a collection of multiple optical images to be displayed in the far field using machine learning (principal component analysis or dictionary learning, etc.). Also, in the example shown in Figure 10, the periods in two mutually orthogonal directions (X and Y directions) differ for each phase modulation region 151, but the period in only one direction (X or Y direction) may also differ for each phase modulation region 151.

[0058] Figure 12 is a conceptual diagram illustrating yet another example of multiple optical images output from multiple phase modulation regions 151. Figure 12 shows a total of four optical images LA arranged in two columns in the X direction and two rows in the Y direction. These are optical images output from a total of four phase modulation regions 151, arranged in two columns in the X direction and two rows in the Y direction. In this example, the optical intensity distribution of the optical image LA output from each of the phase modulation regions 151 includes a sinusoidal distribution that changes periodically along the Y direction. Furthermore, the phase in the Y direction of the sinusoidal optical intensity distribution of the optical image LA output from each of the two phase modulation regions 151 located on one diagonal is different from the phase in the Y direction of the sinusoidal optical intensity distribution of the optical image LA output from each of the two phase modulation regions 151 located on the other diagonal. In this example, the phase of the sinusoidal light intensity distribution presented in the final optical image can be freely changed by changing the ratio of the magnitude of the drive current of two electrodes 161 corresponding to two phase modulation regions 151 located on one diagonal to the magnitude of the drive current of two electrodes 161 corresponding to two phase modulation regions 151 located on the other diagonal. As shown in the example in Figure 12, the phase of the sinusoidal light intensity distribution of the optical image LA output from at least two phase modulation regions 151 may differ from each other in only one direction (Y direction). The light intensity distribution of the optical image LA output from at least two phase modulation regions 151 may include a sinusoidal distribution that changes periodically along two directions (X direction and Y direction). In that case, the phase of the sinusoidal light intensity distribution of at least two optical images LA output from at least two phase modulation regions 151 in each direction may differ from each other between the optical images LA.

[0059] Next, we will explain in detail a phase distribution design method that takes into account the phase synchronization of the optical images output from each of the multiple phase modulation regions 151. In the following explanation, the multiple regions with different refractive indices 15b may be referred to as "multiple points". In other words, the method described below is a method for designing the phase distribution φ(x,y) of two or more phase modulation regions 151 that individually modulate the phase of light at multiple points distributed in two dimensions. Also, in the following explanation, "real space" refers to the space of the phase modulation region 151, and "wavenumber space" refers to the space of the optical image (also called the beam pattern) in the irradiation region. [First design method]

[0060] Figure 13 is a diagram conceptually illustrating the first design method. First, as the first step, initial conditions are set (arrow B1 in the figure). For each phase modulation region 151, a first function 203 is set, which is a complex amplitude distribution function that includes the initial value 201 of the amplitude distribution in wavenumber space and the initial value 202 of the phase distribution in wavenumber space. If the initial value 201 of the amplitude distribution in wavenumber space is F0(kx,ky) and the initial value 202 of the phase distribution in wavenumber space is θ0(kx,ky), then the first function 203 is F0(kx,ky)·e iθ0(kx,ky) It is expressed as follows. In this case, the initial value 201 of the amplitude distribution in wavenumber space may be a predetermined target amplitude distribution 204 in wavenumber space. If the target amplitude distribution 204 in wavenumber space is F0(kx,ky), then its light intensity distribution (i.e., the desired light image) is F0 2 It is given as (kx, ky). Also, the initial value 202 of the phase distribution in wavespace may be a random phase distribution 205.

[0061] Furthermore, in the first step, for each phase modulation region 151, the first function 203 is transformed into a second function 213, which is a complex amplitude distribution function that includes the real-space amplitude distribution 211 and the real-space phase distribution 212, by an inverse Fourier transform such as the Inverse Fast Fourier Transform (IFFT) (arrow B2 in the figure). If the real-space amplitude distribution 211 is A(x,y) and the real-space phase distribution 212 is φ(x,y), then the second function 213 is A(x,y)·eiφ(kx,ky) It is expressed as follows.

[0062] Next, as the second step, the amplitude distribution 211 of the second function 213 in each phase modulation region 151 is replaced with a target amplitude distribution 214 based on a predetermined target intensity distribution in real space (arrows B3 and B4 in the figure). For example, if the predetermined target intensity distribution is A0 2 If (x,y) is given, the target amplitude distribution is given as A0(x,y). In one example, the given target intensity distribution A0 2 (x,y) is constant regardless of x and y, and the target amplitude distribution A0(x,y) is also constant regardless of x and y. In this case, the phase distribution 212 of the second function 213 in each phase modulation region 151 is maintained as is (arrow B5 in the figure). Then, for each phase modulation region 151, the replaced second function 213 is transformed into a third function 223, which is a complex amplitude distribution function that includes the amplitude distribution 221 and the phase distribution 222 in wavespace, by a Fourier transform such as the Fast Fourier Transform (FFT) (arrow B6 in the figure). If the amplitude distribution 221 in wavespace is F(kx,ky) and the phase distribution 222 in wavespace is θ(kx,ky), then the third function 223 is F(kx,ky)·e iθ(kx,ky) It is expressed as follows.

[0063] Next, as the third step, the phase distribution 222 of the third function 223 in each phase modulation region 151 is aligned with the phase distribution 222 of the third function 223 in one of the multiple phase modulation regions 151 (arrow B7 in the figure). At this time, the one phase modulation region 151 that serves as the reference for aligning the phase distributions 222 is arbitrarily determined. Also in this third step, the amplitude distribution 221 of the third function 223 in each phase modulation region 151 is replaced with the target amplitude distribution 204 (arrows B8, B9 in the figure). Then, for each phase modulation region 151, the replaced third function 223 is transformed into a fourth function 233, which is a complex amplitude distribution function that includes the real-space amplitude distribution 231 and the real-space phase distribution 232, by an inverse Fourier transform such as IFFT (arrow B2 in the figure). If the amplitude distribution 231 in real space is A(x,y) and the phase distribution 232 in real space is φ(x,y), then the fourth function 233 is A(x,y)·e iφ(kx,ky) This is expressed as follows. Alternatively, for the phase distribution in wavenumber space of the phase modulation region 151, the average value of the phase of all phase modulation regions 151 can be calculated for each point in wavenumber space, and the same value can be assigned to all points in the phase modulation region.

[0064] Subsequently, the second and third steps are repeated, replacing the second function 213 in the second step with the fourth function 233. Note that, each time the third step is repeated, the position of one phase modulation region 151, which serves as the reference for aligning the phase distributions 222, may be fixed without changing its position. Finally, the phase distribution 232 of the fourth function 233 transformed by the third step is taken as the phase distribution φ(x,y) of each phase modulation region 151 (arrow B10 in the figure).

[0065] As an example, consider a phase modulation layer 15 having a total of four phase modulation regions 151, arranged in two columns in the X direction and two rows in the Y direction, as shown in Figure 14. Of these, two phase modulation regions 151 located on opposite diagonals have phase distribution pattern A, and two phase modulation regions 151 located on the opposite diagonal have phase distribution pattern B. Alternatively, as shown in Figure 15, two phase modulation regions 151 in the first row may have phase distribution pattern B, and two phase modulation regions 151 in the second row may have phase distribution pattern A. Figure 16 is a conceptual diagram showing the design method for phase distribution patterns A and B.

[0066] First, as the first step, we set the initial values ​​(arrow B11 in the figure). That is, for phase distribution pattern A, we set the first function F1(kx,ky)·e, which is a complex amplitude distribution function that includes the initial values ​​of the amplitude distribution F1(kx,ky) in wavespace and the initial values ​​of the phase distribution θ1(kx,ky) in wavespace. iθ1(kx,ky) Set (F1e iθ1 (Abbreviated as ). Furthermore, for phase distribution pattern B, the first function F2(kx,ky)·e is a complex amplitude distribution function that includes the initial values ​​of the amplitude distribution F2(kx,ky) in wavespace and the initial values ​​of the phase distribution θ2(kx,ky) in wavespace. iθ2(kx,ky) Set (hereinafter, F2e iθ2 (This is abbreviated as follows). And the first function F1·e of the phase distribution pattern A. iθ1 This is obtained by an inverse Fourier transform such as IFFT, resulting in a second function A1(x,y)·e, which is a complex amplitude distribution function containing the real-space amplitude distribution A1(x,y) and the real-space phase distribution φ1(x,y). iφ1(x,y) Convert to (arrow B12 in the diagram. Below, A1·e iφ1 (This is abbreviated as follows). Similarly, the first function F2(x,y)·e of phase distribution pattern B iθ2(x,y) This can be transformed using an inverse Fourier transform such as IFFT to obtain the second function A2(x,y)·e, which is a complex amplitude distribution function containing the real-space amplitude distribution A2(x,y) and the real-space phase distribution φ2(x,y). iφ2(x,y) Convert to (arrow B13 in the diagram. Below, A2·e iφ2 (This is abbreviated as ).

[0067] Next, as the second step, the second function A1·e iφ1 The amplitude distribution A1 is a target amplitude distribution A1 based on a predetermined target intensity distribution in real space. ’ Replace it with the second function A2·e iφ2 The amplitude distribution A2 is a target amplitude distribution A2 based on a predetermined target intensity distribution in real space. ’ Replace with (arrow B14 in the figure). At this time, the phase distributions φ1 and φ2 are maintained as they are. Then, the second function A1 after the replacement ’ ·e iφ1 This can be transformed, for example, by a Fourier transform such as FFT, into a third function F1·e, which is a complex amplitude distribution function containing the amplitude distribution F1 in wavespace and the phase distribution θ1 in wavespace. iθ1 Convert to (arrow B15 in the diagram). Similarly, the second function A2 after substitution. ’ ·e iφ2 This can be transformed, for example, by a Fourier transform such as FFT, into a third function F2·e, which is a complex amplitude distribution function containing the amplitude distribution F2 in wavespace and the phase distribution θ2 in wavespace. iθ2 Convert to (arrow B16 in the diagram).

[0068] Next, as the third step, the third function F2·e iθ2 The phase distribution θ2 is given by the third function F1·e iθ1 Align the phase distribution θ1. Also, the third function F1·e iθ1 The amplitude distribution F1, and the third function F2·e iθ2 The amplitude distribution F2 is the target amplitude distribution F1 ’ and F2 ’ Replace them with the following (arrow B17 in the diagram). Then, the third function F1 ’ ·e iθ1 This is then transformed by an inverse Fourier transform such as IFFT into a fourth function A1·e, which is a complex amplitude distribution function containing the real-space amplitude distribution A1 and the real-space phase distribution φ1. iφ1 Convert to (arrow B18 in the diagram). Similarly, the third function F2 ’ ·e iθ1 This is then transformed by an inverse Fourier transform such as IFFT into a fourth function A2·e, which is a complex amplitude distribution function containing the real-space amplitude distribution A2 and the real-space phase distribution φ2. iφ2 Convert to (arrow B19 in the diagram).

[0069] From here on, the second function A1·e in the second step iφ1 And the second function A2·e iφ2 The fourth function A1·e iφ1 And the fourth function A2·e iφ2 Repeat steps 2 and 3, replacing each of them accordingly (arrow B20 in the diagram). Then, the fourth function A1·e transformed by the final step 3 is obtained. iφ1 Let the phase distribution φ1 be the phase distribution φ(x,y) of phase distribution pattern A. Also, the fourth function A2·e transformed by the final third step. iφ2 Let the phase distribution φ2 be the phase distribution φ(x,y) of phase distribution pattern B.

[0070] As another example, consider the phase modulation layer 15 shown in Figure 17, which has a total of m × n phase modulation regions 151, with m columns in the X direction and n rows in the Y direction. The m × n phase modulation regions 151 have different phase distribution patterns. Figure 18 is a diagram that conceptually shows a method for designing the m × n phase distribution patterns.

[0071] First, as the first step, we set the initial values ​​(arrow B41 in the figure). That is, for m × n phase modulation regions 151, we set the amplitude distribution F in wavenumber space. 1,1 (kx,ky)~F m,n The first function F is a complex amplitude distribution function that includes the initial values ​​of (kx,ky) and the initial values ​​of the phase distributions θ1,1(kx,ky)~θm,n(kx,ky) in wavespace, respectively. 1,1 (kx,ky)·e iθ1,1(kx,ky) ~F m,n (kx,ky)·e iθm,n(kx,ky) Set (F below) 1,1 e iθ1,1 ~F m,n e iθm,n (This is abbreviated as follows). Then, for every 151 phase modulation regions, the first function F 1,1 e iθ1,1 ~F m,n e iθm,n The amplitude distribution A in real space can be obtained by an inverse Fourier transform such as IFFT. 1,1 (x,y)~A m,nThe second function A, which is a complex amplitude distribution function containing (x,y) and the phase distributions φ1,1(x,y) to φm,n(x,y) in real space 1,1 (x,y)·e iφ1,1(x,y) ~A m,n (x,y)·e iφm,n(x,y) is converted to (the arrow group B42 in the figure. Hereinafter, A 1,1 e iφ1,1 ~A m,n e iφm,n is abbreviated as).

[0072] Next, as the second step, for each phase modulation region 151, the amplitude distribution A 1,1 e iφ1,1 ~A m,n e iφm,n of the second function A 1,1 ~A m,n is replaced with the target amplitude distribution A ’ 1,1 ~A ’ m,n based on the predetermined target intensity distribution in real space. At this time, the phase distributions φ1,1 to φm,n are maintained as they are. And the replaced second function A ’ 1,1 e iφ1,1 ~A ’ m,n e iφm,n is converted, for each phase modulation region 151, by Fourier transform such as FFT into the third function F 1,1 ~F m,n which is a complex amplitude distribution function containing the amplitude distribution F 1,1 e iθ1,1 ~F m,n e iθm,n in the wavenumber space and the phase distributions θ1,1 to θm,n in the wavenumber space (the arrow group B44 in the figure).

[0073] Next, as the third step, all the phase distributions θ1,1 to θm,n of the third function F 1,1 e iθ1,1 ~F m,n e iθm,n are aligned with the phase distribution θ1,1 of the third function F 1,1 e iθ1,1 . Also, the third function F 1,1 e iθ1,1 ~Fm,n e iθm,n Amplitude distribution F 1,1 ~F m,n The target amplitude distribution F ’ 1,1 ~F ’ m,n Replace them with the following (arrow B45 in the diagram). Then, the third function F ’ 1,1 e iθ1,1 ~F ’ m,n e iθ1,1 The amplitude distribution A in real space can be obtained by an inverse Fourier transform such as IFFT. 1,1 ~A m,n And the fourth function A is a complex amplitude distribution function that includes the real-space phase distributions φ1, 1~φm, and n, respectively. 1,1 e iφ1,1 ~A m,n e iφm,n Convert to (arrow group B46 in the diagram).

[0074] From here on, the second function A of the second step 1,1 e iφ1,1 ~A m,n e iφm,n The fourth function A 1,1 e iφ1,1 ~A m,n e iφm,n Repeat steps 2 and 3, substituting each of the following (arrow B47 in the diagram). Then, the fourth function A transformed by the final step 3 is obtained. 1,1 e iφ1,1 ~A m,n e iφm,n Let the phase distributions φ1,1 to φm, and n be the phase distributions φ(x,y) of each phase modulation region 151. [Second design method]

[0075] Figure 19 is a conceptual diagram illustrating the second design method. Note that the first and second steps are the same as those described in the first design method, so their explanations are omitted.

[0076] In the first third step, the phase distribution 222 of the third function 223 in each phase modulation region 151 is replaced with a predetermined phase distribution that is the same in multiple phase modulation regions 151 (first process, arrow B21 in the figure). The phase values ​​of multiple points (kx, ky) in the predetermined phase distribution may be equal to each other. In this case, the phase values ​​of multiple points (kx, ky) in the predetermined phase distribution may be zero (0 rad). At this time, the amplitude distribution 221 is maintained as is (arrow B22 in the figure). Then, the third function 223 is transformed into the fourth function 233 by an inverse Fourier transform such as IFFT (arrow B2 in the figure).

[0077] The second step is repeated by replacing the second function 213 with the fourth function 233. In the subsequent (second) third step, the amplitude distribution 221 of the third function 223 is replaced with the target amplitude distribution 204 (second process, arrows B23 and B24 in the figure). At this time, the phase distribution 222 is maintained (arrow B25 in the figure). Then, the replaced third function 223 is transformed into the fourth function 233 by an inverse Fourier transform such as IFFT (arrow B2 in the figure).

[0078] Subsequently, the second and third steps are repeated, with the second function 213 in the second step being replaced by the fourth function 233. In the repetition of the third step, the phase distribution 222 is replaced with a predetermined phase distribution (first process), and the amplitude distribution 221 is replaced with the target amplitude distribution 204 (second process) alternately. The predetermined phase distribution may be fixed without changing it during the multiple first processes by repeating the third step. The phase distribution 232 of the fourth function 233 transformed in the final third step is taken as the phase distribution φ(x,y) of each phase modulation region 151 (arrow B10 in the figure).

[0079] As an example, consider a phase modulation layer 15 having a total of four phase modulation regions 151, arranged in two columns in the X direction and two rows in the Y direction, as shown in Figure 14 or Figure 15. Two of these phase modulation regions 151 have phase distribution pattern A, and the other two phase modulation regions 151 have phase distribution pattern B. Figure 20 is a conceptual diagram showing the design method for phase distribution patterns A and B. Note that the first and second steps are the same as the first design method described above, so their explanation will be omitted.

[0080] In the first step 3, the third function F1·e iθ1 The phase distribution θ1 and the third function F2·e iθ2 The phase distribution θ2 is replaced with a predetermined phase distribution θ' common to both phase distribution pattern A and phase distribution pattern B (arrow B31 in the figure). At this time, the amplitude distributions F1 and F2 are maintained as they are. Then, the third function F1·e iθ’ and the third function F2·e iθ’ The fourth function A1·e is obtained by inverse Fourier transform such as IFFT. iφ1 And the fourth function A2·e iφ2 Convert them to the following (arrows B32 and B33 in the diagram).

[0081] Second function A1·e iφ1 And the second function A2·e iφ2 The fourth function A1·e iφ1 And the fourth function A2·e iφ2 Replace each of these and repeat the second step (arrows B34~B36 in the diagram), and in the subsequent (second) third step, the third function F1·e iθ1 The amplitude distribution F1, and the third function F2·e iθ2 The amplitude distribution F2 is the target amplitude distribution F1 ’ and F2 ’ Replace them with the following (arrow B37 in the diagram). Then, the third function F1 ’ ·e iθ1 and the third function F2 ’ ·e iθ2 The fourth function A1·e is obtained by inverse Fourier transform such as IFFT. iφ1 And the fourth function A2·e iφ2 Convert them to the respective values ​​(arrows B38 and B39 in the diagram).

[0082] From here on, the second function A1·e in the second step iφ1 And the second function A2·e iφ2 The fourth function A1·e iφ1 And the fourth function A2·e iφ2 The second and third steps are repeated, replacing each of the following (arrow B20 in the figure). During the repetition of the third step, the replacement of phase distributions θ1 and θ2 (first process, arrow B31 in the figure) and the replacement of amplitude distributions F1 and F2 (second process, arrow B37 in the figure) are performed alternately. Finally, the fourth function A1·e transformed by the third step is obtained. iφ1 Let the phase distribution φ1 be the phase distribution φ(x,y) of phase distribution pattern A. Also, the fourth function A2·e transformed by the final third step. iφ2 Let the phase distribution φ2 be the phase distribution φ(x,y) of phase distribution pattern B.

[0083] As another example, consider the phase modulation layer 15 shown in Figure 17, which has a total of m × n phase modulation regions 151, with m columns in the X direction and n rows in the Y direction. The m × n phase modulation regions 151 have different phase distribution patterns. Figure 21 is a diagram that conceptually shows a method for designing the m × n phase distribution patterns. Note that the first and second steps are the same as the first design method described above, so their explanation will be omitted.

[0084] In the first step 3, the third function F 1,1 e iθ1,1 ~F m,n e iθm,n All phase distributions θ1,1 to θm,n are replaced with a common and predetermined phase distribution θ' (first process, arrow B51 in the figure). At this time, the amplitude distribution F 1,1 ~F m,n This remains unchanged. And the third function F 1,1 e iθ’ ~F m,n e iθ’ The fourth function A is obtained by an inverse Fourier transform such as IFFT. 1,1 e iφ1,1 ~A m,n e iφm,nConvert each to the respective (arrow group B52 in the diagram).

[0085] Second function A 1,1 e iφ1,1 ~A m,n e iφm,n The fourth function A 1,1 e iφ1,1 ~A m,n e iφm,n Replace them respectively and repeat the second step (arrows B53 and group of arrows B54 in the figure), and in the subsequent (second) third step, the third function F 1,1 e iθ1,1 ~F m,n e iθm,n Amplitude distribution F 1,1 ~F m,n The target amplitude distribution F ’ 1,1 ~F ’ m,n Replace them with the following (second process, arrow B55 in the figure). Then, the third function F ’ 1,1 e iθ1,1 ~F ’ m,n e iθm,n The fourth function A is obtained by an inverse Fourier transform such as IFFT. 1,1 e iφ1,1 ~A m,n e iφm,n Convert each to the respective (arrow group B56 in the diagram).

[0086] From here on, the second function A of the second step 1,1 e iφ1,1 ~A m,n e iφm,n The fourth function A 1,1 e iφ1,1 ~A m,n e iφm,n The second and third steps are repeated, replacing each of them (arrow B47 in the figure). In the repetition of the third step, the phase distribution θ1,1 to θm,n is replaced (first process, arrow B51 in the figure), and the amplitude distribution F 1,1 ~F m,n The substitution (second process, arrow B55 in the figure) is performed alternately. Then, the fourth function A is transformed by the final third step. 1,1 eiφ1,1 ~A m,n e iφm,n Let the phase distributions θ1,1 to θm,n be the phase distributions φ(x,y) of each phase modulation region 151.

[0087] The effects obtained by the semiconductor light-emitting element 1A of this embodiment, as described above, will now be explained. In the semiconductor light-emitting element 1A, one or both of the electrode section 16 and the electrode section 17 include multiple electrodes (for example, multiple electrodes 161) that overlap with multiple phase modulation regions 151, respectively. The multiple electrodes are electrically isolated from each other. Therefore, an independent current can be supplied to each of the multiple electrodes. As a result, the light emission intensity of each of the multiple regions of the active layer 12 that supplies light to each of the multiple phase modulation regions 151 is controlled independently, and the light intensity of the multiple optical images LA output from the multiple phase modulation regions 151 is also controlled independently from each other. The multiple optical images LA are irradiated into a common irradiation area. At this time, since the optical images LA output from each of the multiple phase modulation regions 151 are phase-synchronized with each other, the multiple optical images LA can interfere with each other in the common irradiation area. Thus, according to the semiconductor light-emitting element 1A of this embodiment, the multiple optical images LA can be made to interfere with each other while individually adjusting the light intensity of the multiple optical images LA output from the multiple phase modulation regions 151 to form a single final optical image. As a result, the final optical image can be dynamically changed.

[0088] Furthermore, as mentioned above, when the inventors fabricated a semiconductor light-emitting element described in Patent Document 1, spot-shaped stray light unrelated to the intended light image was emitted from the semiconductor light-emitting element along with the intended light image. Figure 22(a) is an image showing a far-field image including spot-shaped stray light observed in the fabricated semiconductor light-emitting element. The inventors experimented to find a structure that could reduce stray light, and found that when the emission wavelength of the active layer 12 was set to 940 nm, providing an InGaAs layer of a certain thickness (for example, 500 nm) between the electrode portion 16 located on the opposite side of the light emission surface and the contact layer 14 made of GaAs significantly reduced stray light. Figure 22(b) is an image showing a far-field image observed in a semiconductor light-emitting element with an InGaAs layer.

[0089] InGaAs exhibits relatively high light absorption at a wavelength of 940 nm. In addition, because InGaAs is lattice mismatched with GaAs, the surface of the InGaAs layer becomes rough. Therefore, it is thought that the absorption and scattering of light emitted from the phase modulation layer 15 to the side opposite the light emission surface before reaching the electrode portion 16 reduces the reflection of light at the electrode portion 16, which leads to a reduction in stray light. In other words, it is thought that the reflection of light at the electrode portion 16 is the cause of stray light. Figure 23 is an image showing the results of observing the vicinity of the contact layer 14 of the semiconductor light-emitting element using a Nomarski microscope. Figure 23(a) shows the case where an InGaAs layer is not provided, and Figure 23(b) shows the case where an InGaAs layer is provided. Referring to Figure 23(a), no light scattering occurs when an InGaAs layer is not provided. In contrast, referring to Figure 23(b), light scattering occurs when an InGaAs layer is provided.

[0090] Furthermore, stray light was not observed in semiconductor light-emitting devices in which the phase modulation layer 15 is not divided into multiple phase modulation regions 151. Therefore, it is presumed that the cause of stray light is that light with a certain phase distribution, emitted from a certain phase modulation region 151 and reflected by the electrode portion 16, mixes with light with a different phase distribution output from an adjacent phase modulation region 151, causing disturbance in the wavefront.

[0091] In the semiconductor light-emitting element 1A of this embodiment, the electrode portion 16 is made of metal, and the reflection reduction structure 41 is configured to reduce the reflection of light emitted from each phase modulation region 151 at the electrode portion 16. Figure 24 is a cross-sectional view showing the configuration of the semiconductor light-emitting element 1B disclosed in Patent Document 1, which does not have the reflection reduction structure 41. As shown in Figure 24, some of the light L1 of the laser light output from each phase modulation region 151 is output as laser light L to the outside of the semiconductor light-emitting element 1B through the back surface 10b and the aperture 17a. On the other hand, the remaining light L2 of the laser light output from the phase modulation region 151 is reflected at the interface between the contact layer 14 and the electrode portion 16. Then, some of the reflected light L3 mixes with the laser light L output from the adjacent phase modulation region 151. This mixing is considered to be the cause of spot-shaped stray light unrelated to the intended optical image. In this embodiment, as shown in Figure 25, the light L2 output from the phase modulation region 151 is scattered by the reflection reduction structure 41. Therefore, the reflection of light L2 is reduced, and the contamination of the laser light L3 with the laser light L output from the adjacent phase modulation region 151 is reduced. Thus, according to this embodiment, spot-shaped stray light can be effectively reduced.

[0092] As in this embodiment, the reflection reduction structure 41 may include a structure that scatters light L2 directed from each phase modulation region 151 toward the electrode portion 16. The scattering structure is provided between both the active layer 12 and the phase modulation layer 15 and the electrode portion 16, and may overlap with a plurality of phase modulation regions 151 when viewed from the stacking direction. By scattering light L2 directed from each phase modulation region 151 toward the electrode portion 16, reflection at the electrode portion 16 can be reduced. Therefore, stray light can be effectively reduced.

[0093] As in this embodiment, the scattering structure may include an uneven structure formed on the surface of the contact layer 14, i.e., the first surface 20a. For example, such a structure can scatter the light L2 directed from each phase modulation region 151 toward the electrode portion 16.

[0094] As in this embodiment, the uneven structure may be caused by lattice mismatch within the semiconductor stack 20. In this case, the uneven structure can be easily formed.

[0095] [First variation] Figure 26 is a cross-sectional view showing the stacked structure of the semiconductor light-emitting element 1C as a first modified example. The semiconductor light-emitting element 1C differs from the first embodiment in the location where the reflection reduction structure is formed. The semiconductor light-emitting element 1C has a reflection reduction structure 42 instead of the reflection reduction structure 41 of the first embodiment. The reflection reduction structure 42 is configured to reduce the reflection of light emitted from each phase modulation region 151 at the electrode portion 16, similar to the reflection reduction structure 41. The reflection reduction structure 42 includes a structure that scatters light L2 (see Figure 25) directed from each phase modulation region 151 toward the electrode portion 16. The scattering structure is provided between both the active layer 12 and the phase modulation layer 15 and the electrode portion 16, and overlaps with a plurality of phase modulation regions 151 when viewed from the stacking direction. The scattering structure includes an uneven structure formed at the interface of two adjacent layers within the semiconductor stack 20. In the illustrated example, the uneven structure is formed at the interface between the cladding layer 13 and the contact layer 14. The details of the uneven structure are the same as those of the uneven structure in the reflection reduction structure 41 of the first embodiment.

[0096] As shown in this modified example, the scattering structure may include an uneven structure formed at the interface of two adjacent layers within the semiconductor stack 20. For example, such a structure can scatter the light L2 directed from each phase modulation region 151 toward the electrode portion 16.

[0097] As shown in this modified example, the uneven structure may be formed at the interface between the cladding layer 13 and the contact layer 14. In this case, the light L2 directed from each phase modulation region 151 toward the electrode portion 16 can be effectively scattered.

[0098] [Second variation] Figure 27 is a cross-sectional view showing the stacked structure of the semiconductor light-emitting element 1D as a second modified example of the above embodiment. The difference between the semiconductor light-emitting element 1D and the above embodiment is that the semiconductor stack 20 has a cladding layer 13A instead of the cladding layer 13. The arrangement of the cladding layer 13A is the same as that of the cladding layer 13 in the above embodiment. The other components of the semiconductor light-emitting element 1D are the same as in the above embodiment, so a detailed explanation is omitted. In this modified example, the electrode portion 16 always includes a plurality of electrodes 161.

[0099] The cladding layer 13A includes a high-resistance region 21 and a basic region 22. The configuration of the basic region 22 is the same as that of the cladding layer 13 in the above embodiment. The high-resistance region 21 has a higher resistivity than the basic region 22. The high-resistance region 21 may be made of an insulator.

[0100] The high-resistance region 21 is located between adjacent phase-modulation regions 151 when viewed from the stacking direction of the semiconductor stack 20. Furthermore, the high-resistance region 21 is provided on the connection region 152 of the phase-modulation layer 15. The region formed by projecting the high-resistance region 21 onto a virtual plane P is included in the region formed by projecting the connection region 152 onto the virtual plane P. In the illustrated example, when the phase-modulation layer 15 is provided between the cladding layer 13A and the active layer 12, the high-resistance region 21 extends from the interface near the first surface 20a of the cladding layer 13A to the cap region 15c of the phase-modulation layer 15. However, the high-resistance region 21 does not contact the basic region 15a or the different refractive index region 15b. In other words, in the stacking direction (Z direction) of the semiconductor stack 20, a gap is provided between the high-resistance region 21 and the basic region 15a and the different refractive index region 15b.

[0101] Figure 28 is a plan view (viewed from the thickness direction) of the cladding layer 13A. As described above, the cladding layer 13A includes a high-resistance region 21 and a basic region 22. The planar shape of the high-resistance region 21, as viewed from the stacking direction of the semiconductor stack 20, is, for example, a grid. The basic region 22 is provided inside each of the multiple openings 21a of the grid-shaped high-resistance region 21.

[0102] The planar shape of each of the multiple openings 21a is, for example, a square or a rectangle. Viewed from the stacking direction of the semiconductor stack 20, each of the multiple openings 21a overlaps with the corresponding phase modulation region 151. The high-resistance region 21 includes a portion 21b provided between adjacent phase modulation regions 151 when viewed from the stacking direction of the semiconductor stack 20, and an outer frame-shaped portion 21c that encloses the multiple phase modulation regions 151 together.

[0103] In Figure 27, the high-resistance region 21 penetrates the basic region 22 and reaches the phase modulation layer 15, but the high-resistance region 21 does not necessarily have to reach the phase modulation layer 15. In that case, the lowest end of the high-resistance region 21 is located within the basic region 22.

[0104] As shown in this modified example, the cladding layer of the semiconductor stack may include a high-resistance region 21 located between adjacent phase-modulated regions 151 when viewed from the stacking direction of the semiconductor stack. In this case, leakage of the current flowing between each electrode 161 and the region of the active layer 12 located directly beneath each electrode 161 to the region of the active layer 12 located directly beneath the adjacent electrode 161 can be reduced.

[0105] As shown in this modified example, the high-resistance region 21 may extend from the interface on the first surface 20a side of the cladding layer 13A to the phase modulation layer 15. In this case, current leakage can be prevented over the entire thickness of the cladding layer 13A.

[0106] As shown in this modified example, the planar shape of the high-resistance region 21 as viewed from the stacking direction of the semiconductor stack 20 may be grid-like. In this case, the high-resistance region 21 can be provided between all the phase modulation regions 151 as viewed from the stacking direction.

[0107] [Third variation] Figure 29 is a cross-sectional view showing the configuration of a semiconductor light-emitting element 1E as a third modified example of the above embodiment. The semiconductor light-emitting element 1E differs from the above embodiment in that it includes a phase modulation layer 15A instead of the phase modulation layer 15, and includes a λ / 4 plate 24. The λ / 4 plate 24 extends along a virtual plane P and is positioned opposite the back surface 10b of the semiconductor substrate 10, i.e., the light-emitting surface of the semiconductor light-emitting element 1E. The axis of the λ / 4 plate 24 is perpendicular to the straight line D shown in Figures 3 and 4.

[0108] Figure 30 is a plan view showing the phase modulation layer 15A. The phase modulation layer 15A has a phase shift region 153 in addition to the configuration of the phase modulation layer 15 of the above embodiment. The phase shift region 153 is provided between adjacent phase modulation regions 151. In the illustrated example, the phase shift region 153 is provided inside a portion 152b of the connection region 152 and consists of a plurality of portions extending along the X direction and a plurality of portions extending along the Y direction that intersect each other. The planar shape of the phase shift region 153 as viewed from the stacking direction of the semiconductor stack 20 is, for example, a grid.

[0109] Figure 31 is a plan view showing a partially enlarged view of the phase shift region 153 and the surrounding connection region 152. As shown in Figure 31, the phase shift region 153 is provided between a square grid set in the connection region 152 located on one side of the phase shift region 153 and a square grid set in the connection region 152 located on the other side. The phase shift region 153 has an arbitrary width. Depending on the width of the phase shift region 153, the square grids of the connection region 152 located on one side of the phase shift region 153 and the square grids of the connection region 152 located on the other side are shifted relative to each other. These square grids are common to the square grids set in the phase modulation region 151 adjacent to the connection region 152. Therefore, the square grids of adjacent phase modulation regions 151 are shifted relative to each other.

[0110] In one example, when the lattice constant of a square lattice is a, the phase-shift region 153 has a width of n·a+a / 2 (where n is a non-negative integer). As a result, the square lattice of the connection region 152 located on one side of the phase-shift region 153 and the square lattice of the connection region 152 located on the other side are shifted by n·a+a / 2. Consequently, the square lattices of adjacent phase-modulation regions 151 are also shifted by n·a+a / 2. In this case, the phases of the optical images LA output from each of the adjacent phase-modulation regions 151 are shifted by π (rad). Therefore, by these optical images LA passing through the λ / 4 plate 24, it is possible to output circularly polarized light with opposite rotations from each of the adjacent phase-modulation regions 151. This makes it possible to electrically change the intensity ratio of left-handed and right-handed circularly polarized light. Such a semiconductor light-emitting device can be used, for example, as a light source for optical quantum communication or a quantum computer.

[0111] [Fourth variation] The areas of multiple different refractive index regions 15b in a cross-section perpendicular to the thickness direction of the phase modulation layer 15 may be set individually according to a predetermined optical image LA. In this case, not only the phase but also the light intensity can be adjusted for each different refractive index region 15b, thereby increasing the design flexibility of the optical image LA. Figure 32 is a magnified view of one unit constituent region R. In the example shown in this figure, the area of ​​the different refractive index region 15b is largest when the centroid G of the different refractive index region 15b coincides with the grid point O, and the area of ​​the different refractive index region 15b decreases as the centroid G of the different refractive index region 15b moves away from the grid point O (i.e., as the distance r(x,y) increases). In this way, the area of ​​the different refractive index region 15b may be changed according to the relative position of the centroid G of the different refractive index region 15b with respect to the grid point O. This makes it possible to keep the light intensity constant regardless of the phase distribution φ(x,y).

[0112] [Second Embodiment] Figure 33 is a cross-sectional view showing the stacked structure of the semiconductor light-emitting element 1F according to the second embodiment. The semiconductor light-emitting element 1F includes a light-absorbing layer 43 instead of the reflection reduction structure 41 of the above embodiment. The light-absorbing layer 43 is a reflection reduction structure in this embodiment, configured to reduce the reflection of light emitted from each phase modulation region 151 at the electrode portion 16. The light-absorbing layer 43 is provided between both the active layer 12 and the phase modulation layer 15 and the electrode portion 16, and overlaps with a plurality of phase modulation regions 151 when viewed from the stacking direction. The light-absorbing layer 43 contains a material with higher light absorption than the contact layer 14 and absorbs light L2 (see Figure 25) directed from each phase modulation region 151 toward the electrode portion 16. However, the light-absorbing layer 43 is made of a material that is conductive and does not hinder carrier injection from the electrode portion 16 to the active layer 12. The light-absorbing layer 43 is provided in the semiconductor stack 20 and constitutes one of the layers of the semiconductor stack 20. In this embodiment, the light-absorbing layer 43 is provided between the contact layer 14 and the electrode portion 16. The light-absorbing layer 43 has a light absorption rate of 50% or more at the emission wavelength of the active layer 12. The thickness of the light-absorbing layer 43 is, for example, 100 nm or more.

[0113] In one embodiment, when the emission wavelength of the active layer 12 is 940 nm (wavelength energy of 1.319 eV), the semiconductor substrate 10 is, for example, a GaAs substrate, and the contact layer 14 is, for example, a GaAs layer. In this case, the light absorption layer 43 is, for example, InAs, GaSb, InSb, In x Ga 1-x As (0.2 ≤ x ≤ 1), In x Ga 1-x Sb(0≦x≦1), GaAs x S 1-x (0≦x≦0.8), InAs x S 1-x (0≦x≦1), InAs x P 1-x (0.1 ≤ x ≤ 1), GaP x S 1-x (0≦x≦0.5), InP x S 1-x (0≦x≦0.9), In x Ga 1-x As y P 1-y(0≦x≦1, 0≦y≦1), and In 1-x-y Al x Ga y It includes at least one material selected from the group As(0≦x≦1, 0≦y≦1).

[0114] In another embodiment, when the emission wavelength of the active layer 12 is 640 nm (wavelength energy of 1.938 eV), the semiconductor substrate 10 is, for example, a GaAs substrate, and the contact layer 14 is, for example, a GaAs layer. In this case, the light absorption layer 43 is, for example, GaAs, InAs, InP, GaSb, InSb, In x Ga 1-x As (0 ≤ x ≤ 1), In x Ga 1-x P(0.6≦x≦1), In x Ga 1-x Sb(0≦x≦1), GaAs x S 1-x (0≦x≦1), InAs x S 1-x (0≦x≦1), GaAs x P 1-x (0.6≦x≦1), InAs x P 1-x (0≦x≦1), GaP x S 1-x (0≦x≦0.7), InP x S 1-x (0≦x≦1), In x Ga 1-x As y P 1-y (0≦x≦1, 0≦y≦1), and In 1-x-y Al x Ga y It includes at least one material selected from the group As(0≦x≦1, 0≦y≦1). In yet another embodiment, when the emission wavelength of the active layer 12 is 1550 nm (wavelength energy of 0.800 eV), the semiconductor substrate 10 is, for example, an InP substrate, and the contact layer 14 is, for example, In 0.53 Ga 0.47 This is an As layer. In this case, the light-absorbing layer 43 is, for example, InAs, InSb, In x Ga 1-x As (0.6 ≤ x ≤ 1), Inx Ga 1-x Sb(0.1≦x≦1), GaAs x S 1-x (0.1≦x≦0.4), InAs x P 1-x (0≦x≦1), GaP x S 1-x (0.1 ≤ x ≤ 0.2), InP x S 1-x (0≦x≦0.7), In x Ga 1-x As y P 1-y (0≦x≦1, 0≦y≦1), and In 1-x-y Al x Ga y It includes at least one material selected from the group As(0≦x≦1, 0≦y≦1).

[0115] In this embodiment, a light-absorbing layer 43 is provided in the semiconductor stack 20. Thus, the reflection reduction structure may be provided between both the active layer 12 and the phase modulation layer 15 and the electrode portion 16, and may include a structure that overlaps with a plurality of phase modulation regions 151 when viewed from the stacking direction, and absorbs light L2 directed from each phase modulation region 151 toward the electrode portion 16. By absorbing light L2 directed from each phase modulation region 151 toward the electrode portion 16, reflection at the electrode portion 16 can be reduced. Therefore, stray light can be effectively reduced.

[0116] As in this embodiment, the absorbing structure may include a light-absorbing layer 43 provided in the semiconductor stack 20. For example, such a structure can absorb light L2 directed from each phase modulation region 151 toward the electrode portion 16.

[0117] As in this embodiment, the light absorption layer 43 may be provided between the contact layer 14 and the electrode portion 16. In this case, the light L2 directed from each phase modulation region 151 toward the electrode portion 16 can be effectively absorbed.

[0118] As in this embodiment, the light absorption layer 43 may have a light absorption rate of 50% or more at the emission wavelength of the active layer 12. In this case, light directed from each phase modulation region 151 toward the electrode portion 16 can be effectively absorbed.

[0119] [Fifth variation] Figure 34 is a cross-sectional view showing the stacked structure of the semiconductor light-emitting element 1G as a fifth modified example. The semiconductor light-emitting element 1G differs from the second embodiment in the position where the light-absorbing layer is provided. The semiconductor light-emitting element 1G has a light-absorbing layer 44 instead of the light-absorbing layer 43 of the second embodiment. The light-absorbing layer 44 is provided between the cladding layer 13 and the contact layer 14. The configuration of the light-absorbing layer 44, excluding its position, is the same as that of the light-absorbing layer 43.

[0120] As shown in this modified example, the light absorption layer 44 may be provided between the cladding layer 13 and the contact layer 14. In this case as well, the light L2 (see Figure 25) directed from each phase modulation region 151 toward the electrode portion 16 can be effectively absorbed.

[0121] [Sixth variation] Figure 35 is a cross-sectional view showing the stacked structure of the semiconductor light-emitting element 1H as a sixth modified example. The semiconductor light-emitting element 1H differs from the second embodiment in that it includes a contact layer 46 instead of the contact layer 14, and the contact layer 46 functions as a light-absorbing layer. That is, the semiconductor stack 20 of this modified example includes a contact layer 46 as a light-absorbing layer. The constituent material of the contact layer 46 is the same as the constituent material of the light-absorbing layer 43 in the second embodiment.

[0122] As shown in this modified example, the semiconductor stack 20 may include a contact layer 46 as a light-absorbing layer. In this case as well, light L2 (see Figure 25) directed from each phase modulation region 151 toward the electrode portion 16 can be effectively absorbed.

[0123] [Third Embodiment] Figure 36 is a cross-sectional view showing the stacked structure of a semiconductor light-emitting element 1J according to a third embodiment of the present disclosure. The semiconductor light-emitting element 1J does not have the reflection reduction structure 41 of the first embodiment. Instead, the semiconductor light-emitting element 1J includes a transparent electrode portion 45 as a reflection reduction structure instead of a metal electrode portion 16. The transparent electrode portion 45 has a structure that transmits light L2 from each phase modulation region 151. Specifically, the transparent electrode portion 45 has a light transmittance of 50% or more at the emission wavelength of the active layer 12. The transparent electrode portion 45 includes a plurality of electrodes 451. The configuration of the plurality of electrodes 451 is the same as that of the electrode 161 of the first embodiment, except that it is light-transmitting. Examples of materials for the transparent electrode portion 45 include ITO, ZnO:Al(AZO), or ZnO:Ga(GZO).

[0124] As in this embodiment, the reflection reduction structure may include a structure that transmits light L2 from each phase modulation region 151 in the transparent electrode portion 45. By transmitting light L2 from each phase modulation region 151 through the transparent electrode portion 45, the reflection of light L2 can be reduced. Therefore, stray light can be effectively reduced. A metal layer of a thickness that does not hinder transmission (does not contribute to reflection) may be provided between the contact layer 14 and the transparent electrode portion 45.

[0125] As in this embodiment, the transparent electrode portion 45 may have a light transmittance of 50% or more at the emission wavelength of the active layer 12. In this case, the transparent electrode portion 45 can effectively transmit light L2 from each phase modulation region 151.

[0126] The semiconductor light-emitting element according to this disclosure is not limited to the embodiments described above, and various other modifications are possible. For example, each of the embodiments described above may be combined with one another depending on the required purpose and effect. That is, the semiconductor light-emitting element may include at least two of the reflection reduction structure 41 of the first embodiment, the reflection reduction structure 42 of the first modified example, the light absorption layer 43 of the second embodiment, the light absorption layer 44 of the fifth modified example, the contact layer 14 of the sixth modified example, and the transparent electrode portion 45 of the third embodiment. In that case, stray light can be further reduced.

[0127] Furthermore, the reflection reduction structure that reduces the reflection of light L2 emitted from each phase modulation region 151 is not limited to the embodiments and modifications described above, but may have other structures. [Explanation of symbols]

[0128] 1A~1H,1J…Semiconductor light-emitting element, 10…Semiconductor substrate, 10a…Main surface, 10b…Back surface, 11…Cladding layer, 12…Active layer, 13…Cladding layer, 14,46…Contact layer, 15,15A…Phase modulation layer, 15a…Basic region, 15b…Different refractive index region, 15c…Cap region, 16…Electrode section (first electrode section), 17…Electrode section (second electrode section), 17a…Aperture, 18…Protective film, 19…Anti-reflective film, 20…Semiconductor stacking, 20a…First surface, 20b…Second surface, 21…High resistance region, 22…Basic region, 24…λ / 4 plate, 31…Drive circuit, 32…Power supply circuit, 33~35…Wiring, 41,42…Reflection reduction structure, 43,44…Light absorption layer, 45…Transparent electrode section, 151…Phase modulation Region, 152...connection region, 152a...aperture, 152b,152c...part, 153...phase shift region, 161,451...electrodes, 201...initial value of amplitude distribution in wavenumber space, 202...initial value of phase distribution in wavenumber space, 203...first function, 204...target amplitude distribution, 205...random phase distribution, 211...amplitude distribution in real space, 212...phase distribution in real space, 213...second function, 214...target amplitude distribution, 221...amplitude distribution in wavenumber space, 222...phase distribution in wavenumber space, 223...third function, 231...amplitude distribution in real space, 232...phase distribution in real space, 233...fourth function, D...line, G...centroid, L...laser light, LA...optical image, O...lattice point, P...virtual plane, R...unit constituent region.

Claims

1. A semiconductor laminate having a laminated structure including an active layer and a phase modulation layer between a first surface and a second surface, wherein the phase modulation layer has a plurality of phase modulation regions arranged along a virtual plane perpendicular to the thickness direction of the phase modulation layer and optically coupled to one another, and each of the plurality of phase modulation regions includes a basic region having a first refractive index and a plurality of different refractive index regions provided within the basic region and having a second refractive index different from the first refractive index, and distributed two-dimensionally along the virtual plane, A first electrode portion facing the first surface of the semiconductor stack, A second electrode portion facing the second surface of the semiconductor stack, Equipped with, One or both of the first electrode portion and the second electrode portion include a plurality of electrodes that overlap with the plurality of phase modulation regions when viewed from the stacking direction of the semiconductor stack, and the plurality of electrodes are electrically isolated from each other. The light output from the active layer resonates along the virtual plane in each of the plurality of phase modulation regions of the phase modulation layer, and is irradiated from each of the plurality of phase modulation regions to an irradiation region located in a direction intersecting both the first and second surfaces of the semiconductor stack via the second surface. A semiconductor light-emitting element having a reflection-reducing structure configured to reduce the reflection of light emitted from each phase modulation region at the first electrode portion.

2. The semiconductor light-emitting element according to claim 1, wherein the reflection reduction structure is provided between both the active layer and the phase modulation layer and the first electrode portion, and includes a structure that overlaps with the plurality of phase modulation regions when viewed from the stacking direction and scatters light from each phase modulation region toward the first electrode portion.

3. The semiconductor light-emitting element according to claim 2, wherein the scattering structure includes an uneven structure formed at the interface of two adjacent layers within the semiconductor stack or on the first surface.

4. The semiconductor stack includes a cladding layer provided on the active layer and the phase modulation layer, and a contact layer provided on the cladding layer and adjacent to the cladding layer. The semiconductor light-emitting element according to claim 3, wherein the uneven structure is formed at the interface between the cladding layer and the contact layer.

5. The semiconductor light-emitting element according to claim 3 or 4, wherein the uneven structure is caused by lattice mismatch within the semiconductor stack.

6. The semiconductor light-emitting element according to claim 1, wherein the reflection reduction structure is provided between both the active layer and the phase modulation layer and the first electrode portion, and overlaps with the plurality of phase modulation regions when viewed from the stacking direction, and includes a structure that absorbs light from each phase modulation region toward the first electrode portion.

7. The semiconductor light-emitting element according to claim 6, wherein the absorbing structure includes a light-absorbing layer provided in the semiconductor stack.

8. The semiconductor stack includes a cladding layer provided on the active layer and the phase modulation layer, and a contact layer provided on the cladding layer. The semiconductor light-emitting element according to claim 7, wherein the light-absorbing layer is provided between the cladding layer and the contact layer, or between the contact layer and the first electrode portion.

9. The semiconductor light-emitting element according to claim 7, wherein the semiconductor stack includes a cladding layer provided on the active layer and the phase modulation layer, and a contact layer provided on the cladding layer as the light-absorbing layer.

10. The semiconductor light-emitting element according to any one of claims 7 to 9, wherein the light-absorbing layer has a light absorption rate of 50% or more at the emission wavelength of the active layer.

11. The semiconductor light-emitting element according to claim 1, wherein the reflection reduction structure includes a structure that transmits light from each phase modulation region in the first electrode portion.

12. The semiconductor light-emitting element according to claim 11, wherein the first electrode portion has a light transmittance of 50% or more at the emission wavelength of the active layer.

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