Optical and Light Emitting Devices

Abstract

An optical device according to one embodiment has a structure capable of outputting light in a short-wavelength range such as a visible range. This optical device is provided with a UC layer, a first light confinement layer, a second light confinement layer, and a resonant mode forming layer. The UC layer includes an upconversion material that, upon receiving excitation light in a first wavelength range, outputs light in a second wavelength range shorter than the first wavelength range. The first light confinement layer has a light reflection characteristic of reflecting at least part of the light in the second wavelength range. The second light confinement layer has a light reflection characteristic of reflecting part of the light in the second wavelength range and transmitting the remainder, and is disposed such that the UC layer is located between the first and second light confinement layers. The resonant mode layer is provided between the UC layer and the first light confinement layer or between the UC layer and the second light confinement layer, includes a basic layer and a plurality of different refractive index regions, and forms the resonant mode of the light in the second wavelength range.

Description

[Technical field]

[0001] The present disclosure relates to optical and light emitting devices. This application claims priority from Japanese Patent Application No. 2020-094937, filed on May 29, 2020, the contents of which are relied upon and incorporated herein by reference in their entirety. [Background technology]

[0002] Patent Document 1 discloses a technology related to a semiconductor light-emitting device. This semiconductor light-emitting device includes a first conductive type semiconductor layer and a second conductive type semiconductor layer provided on a main surface of a substrate, an active layer sandwiched between the first conductive type semiconductor layer and the second conductive type semiconductor layer and generating light when carriers are injected, a two-dimensional diffraction grating provided on a reference plane parallel to the main surface of the substrate and defining the wavelength of light to be generated in the active layer, and a light emission surface provided parallel to the main surface of the substrate and emitting the light generated in the active layer. The two-dimensional diffraction grating has, for example, a portion of a second refractive index provided so as to form a two-dimensional diffraction grating in a medium having a first refractive index, and the first refractive index is greater than the second refractive index. The two-dimensional diffraction grating is, for example, either a triangular lattice or a square lattice. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2000-332351 A [Non-patent literature]

[0004] [Non-Patent Document 1] Jing Zhou et al., "Upconversion Luminescent Materials: Advances and Applications", Chemical Reviews, 115, pp. 395-465, (2015) [Non-Patent Document 1] Y. Kurosaka et al., "Effects of non-lasing band in two-dimensional photonic-crystal lasers clarified using omnidirectional band structure," Opt. Express 20, 21773-21783 (2012) Summary of the Invention [Problem to be solved by the invention]

[0005] As a result of examining the above-mentioned conventional techniques, the inventors have found the following problem. That is, in a surface-emitting light-emitting element that outputs laser light in a direction intersecting with the main surface of the substrate, a layer that forms a resonance mode in a direction along the main surface of the substrate (e.g., a photonic crystal layer, hereinafter referred to as a "PC layer") may be provided near the active layer. However, in a relatively short wavelength region such as the green or blue region, a practical photonic crystal surface-emitting laser or phase-modulated light-emitting element (static-iPMSEL) has not yet been realized.

[0006] Specifically, in the case of a light-emitting element mainly including a GaAs-based semiconductor, the emission wavelength is, for example, in the near-infrared region, and a light-emitting element having practical optical output characteristics (for example, a low threshold current value) has been realized. However, in the case of a light-emitting element mainly including a nitride semiconductor such as GaN, the emission wavelength is, for example, in the green region to the blue region, but due to the characteristics of the material, the optical confinement coefficient of the layer forming the resonance mode is too small, so a photonic crystal surface-emitting laser or phase-modulated light-emitting element having practical optical output characteristics has not yet been realized. In order to enrich color expression in the visible region, it is desired to realize a practical photonic crystal surface-emitting laser or phase-modulated light-emitting element that can output light having a wavelength shorter than the red region, for example, in the green region to blue region.

[0007] The present disclosure has been made to solve the above-mentioned problems, and aims to provide an optical device as a practical photonic crystal surface-emitting laser or phase-modulated light-emitting element capable of outputting light in a relatively short wavelength region such as the green or blue region, and a light-emitting device including the optical device. As an example, the present disclosure aims to provide a light-emitting device in which the optical device is applied to a photonic crystal surface-emitting laser or a phase-modulated light-emitting element as an excitation light source. [Means for solving the problem]

[0008] The optical device of the present disclosure includes an upconversion layer (hereinafter, referred to as "UC layer"), a first optical confinement layer (a light-reflecting layer or a single layer of a multilayer stack structure), a second optical confinement layer (a light-reflecting layer or a single layer of a multilayer stack structure), and a resonant mode forming layer. The UC layer includes an upconversion material that receives excitation light included in a first wavelength range and outputs light in a second wavelength range shorter than the first wavelength range. The first optical confinement layer has an optical reflectance property that reflects at least a part of the light in the second wavelength range. The second optical confinement layer has an optical reflectance property that reflects a part of the light in the second wavelength range and transmits the remainder. The second optical confinement layer is disposed such that the UC layer is located between the first optical confinement layer and the second optical confinement layer. That is, the second optical confinement layer is disposed on the opposite side of the first optical confinement layer with respect to the UC layer. The resonant mode forming layer is provided between the first optical confinement layer and the UC layer, or between the second optical confinement layer and the UC layer. The resonance mode layer includes a base layer and a plurality of modified refractive index areas that have a refractive index different from that of the base layer and are two-dimensionally distributed on a reference plane perpendicular to a thickness direction of the resonance mode forming layer, whereby the resonance mode forming layer forms a resonance mode of light in a second wavelength range along the reference plane. Effect of the Invention

[0009] According to the light-emitting device and the like of the present disclosure, it is possible to provide a practical photonic crystal surface-emitting laser and the like that can output light in a relatively short wavelength range, such as the visible range. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing a cross-sectional structure of the light-emitting device according to the first embodiment. [Diagram 2] FIG. 2 is a plan view of the PC layer. [Diagram 3] FIG. 3(a) to FIG. 3(g) are diagrams showing examples of the shape of the modified refractive index area (part 1). [Figure 4] FIG. 4(a) to FIG. 4(k) are diagrams showing examples of the shapes of the modified refractive index areas (part 2). [Diagram 5] FIG. 5(a) to FIG. 5(k) are diagrams showing examples of the shapes of the modified refractive index areas (part 3). [Figure 6] FIG. 6 is a diagram showing a cross-sectional structure of the light-emitting device according to the second embodiment. [Figure 7] FIG. 7 is a plan view of the phase modulation layer. [Figure 8] FIG. 8 is an enlarged view of a part of the phase modulation layer. [Figure 9] FIG. 9 is a diagram for explaining the relationship between an optical image obtained by focusing an output beam pattern of an optical device and a rotation angle distribution in a phase modulation layer. [Figure 10] FIG. 10 is a diagram for explaining coordinate conversion from spherical coordinates to coordinates in an XYZ orthogonal coordinate system. [Figure 11] FIG. 11 is a plan view showing an example in which the refractive index structure of FIG. 7 is applied only within a specific region of a phase modulation layer. [Figure 12] 12(a) and 12(b) are diagrams for explaining points to keep in mind when determining the arrangement of each modified refractive index area and performing calculations using a general discrete Fourier transform (or fast Fourier transform). [Figure 13] 13(a) to 13(d) are diagrams showing examples of beam patterns (optical images) output from a GaAs-based S-iPM laser in the near-infrared wavelength band. [Figure 14] FIG. 14 is a plan view of a phase modulation layer serving as a resonance mode forming layer included in the optical device according to the third embodiment. [Figure 15] FIG. 15 is a diagram showing the positional relationship of modified refractive index areas in a phase modulation layer. [Figure 16] FIG. 16 is a diagram showing a cross-sectional structure of a light-emitting device according to a first modification. [Figure 17] 17A to 17C are cross-sectional views showing a manufacturing process for a light emitting device according to the second modification. [Figure 18] FIG. 18 is a diagram showing a cross-sectional structure of a light-emitting device according to a third modified example. [Figure 19] FIG. 19 is a diagram showing a cross-sectional structure of a light-emitting device according to a fourth modified example. [Figure 20] 20A to 20C are cross-sectional views showing a manufacturing process for a light emitting device according to the fifth modification. [Figure 21] FIG. 21 is a diagram showing a cross-sectional structure of a light-emitting device according to a sixth modified example. [Figure 22] FIG. 22 is a diagram showing a cross-sectional structure of a light-emitting device according to a seventh modification. [Figure 23] FIG. 23 is a diagram showing a cross-sectional structure of a light-emitting device according to an eighth modification. [Figure 24] FIG. 24 is a plan view showing the reciprocal lattice space for the PC layer of a PCSEL that lases at the Γ point. [Diagram 25] FIG. 25 is a perspective view showing the reciprocal lattice space shown in FIG. 24 in a three-dimensional manner. [Figure 26] FIG. 26 is a plan view showing the reciprocal lattice space for the PC layer of a PCSEL lasing at point M. [Figure 27] FIG. 27 is a plan view showing a reciprocal lattice space for the phase modulation layer of an S-iPM laser oscillating at the Γ point. [Figure 28] FIG. 28 is a perspective view showing the reciprocal lattice space shown in FIG. 13 in a three-dimensional manner. [Figure 29] FIG. 29 is a plan view showing a reciprocal lattice space related to a phase modulation layer of an S-iPM laser oscillating at point M. [Diagram 30]FIG. 30 is a conceptual diagram for explaining the operation of adding a diffraction vector having a certain magnitude and direction to an in-plane wave vector. [Diagram 31] FIG. 31 is a diagram for explaining a schematic structure surrounding a light line. [Diagram 32] FIG. 32 is a diagram conceptually showing an example of the rotation angle distribution. [Diagram 33] FIG. 33 is a diagram showing an example of the rotation angle distribution of the phase modulation layer. [Diagram 34] FIG. 34 is an enlarged view of a portion S shown in FIG. [Diagram 35] FIG. 35 shows a beam pattern (optical image) output from a semiconductor light emitting element having the rotation angle distribution shown in FIG. [Diagram 36] FIG. 36 is a schematic diagram of the beam pattern shown in FIG. [Figure 37] FIG. 37(a) is a schematic diagram of a beam pattern, and FIG. 37(b) is a diagram showing the phase distribution of the beam pattern. [Figure 38] FIG. 38(a) is a schematic diagram of a beam pattern, and FIG. 38(b) is a diagram showing the phase distribution of the beam pattern. [Figure 39] FIG. 39(a) is a schematic diagram of a beam pattern, and FIG. 39(b) is a diagram showing the phase distribution of the beam pattern. [Diagram 40] FIG. 40 is a schematic diagram for explaining the cross-sectional structure of the light-emitting device according to the fourth embodiment in comparison with the light-emitting device according to the first embodiment. [Diagram 41] FIG. 41 is a diagram for explaining a manufacturing process of an excitation light source (light source section) in the first manufacturing method (unit assembly type) of the light emitting device according to the fourth embodiment. [Diagram 42] 42(a) and 42(b) are diagrams for explaining the step of mounting an excitation light source on a submount in the first manufacturing method. [Diagram 43]Figures 43(a) and 43(b) are diagrams for explaining the optical device (resonator portion) manufacturing process in the first manufacturing method, and Figure 43(c) is a diagram for explaining the optical device mounting process on a submount already having an excitation light source mounted thereon in the first manufacturing method. [Diagram 44] FIG. 44(a) is a plan view of a light-emitting device manufactured by the first manufacturing method (unit assembly type), and FIG. 44(b) is a cross-sectional view of the light-emitting device taken along the line indicated by arrow II in FIG. 44(a). [Diagram 45] Figure 45(a) is a cross-sectional view of a light-emitting device having an optical confinement layer of a first structure manufactured by a first manufacturing method, and Figure 45(b) is a cross-sectional view of a light-emitting device having an optical confinement layer of a second structure manufactured by the first manufacturing method. [Figure 46] Figure 46(a) is a cross-sectional view of a light-emitting device having an optical confinement layer of a third structure manufactured by the first manufacturing method, and Figure 46(b) is a cross-sectional view of a light-emitting device having an optical confinement layer of a fourth structure manufactured by the first manufacturing method. [Figure 47] FIG. 47 is a diagram for explaining design guidelines for an optical device (resonator part model). [Figure 48] FIG. 48 is a graph showing the relationship between the Fourier coefficient and the FF value for various hole shapes in the PC layer of an optical device having the cross-sectional structure shown in FIG. [Figure 49] Figures 49(a) and 49(b) show an example of a cross-sectional structure that can increase the diffraction intensity κ2,0 and the distribution ratio ΓUC, respectively. Figure 49(c) is a table showing the calculation results of the diffraction intensity κ2,0 and the distribution ratio ΓUC for an optical device having the cross-sectional structure shown in Figures 49(a) and 49(b). Figures 49(d) and 49(e) are diagrams for explaining the hole shapes applied in the calculations. [Figure 50]Figure 50(a) shows an example of the cross-sectional structure of an optical device prepared for investigating the thickness dependence of the UC layer, Figure 50(b) shows the hole shape applied for the investigation, and Figures 50(c) to 50(f) are tables showing the calculation results of the diffraction intensity κ2,0, distribution ratio ΓPC, distribution ratio ΓUC, and effective refractive index neff. [Figure 51] FIG. 51 is a table summarizing the dependence of the thickness of the optical confinement layer on the thickness of the PC layer for the optical device having the cross-sectional structure shown in FIG. 50(a). [Figure 52] Figure 52(a) shows an example of the cross-sectional structure of an optical device prepared for study, and Figures 52(b) to 52(e) are tables showing the calculation results of the diffraction intensity κ2,0, distribution ratio ΓPC, distribution ratio ΓUC, and effective refractive index neff. [Diagram 53] Figure 53(a) is a cross-sectional view of a light-emitting device having an optical confinement layer of a first structure manufactured by the second manufacturing method (upconversion material injection type) of the light-emitting device according to the fourth embodiment, and Figure 53(b) is a cross-sectional view of a light-emitting device having an optical confinement layer of a second structure manufactured by the second manufacturing method. [Figure 54] Figure 54(a) is a cross-sectional view of a light-emitting device having an optical confinement layer of a third structure manufactured by the second manufacturing method, and Figure 54(b) is a cross-sectional view of a light-emitting device having an optical confinement layer of a fourth structure manufactured by the second manufacturing method. [Figure 55] 55(a) to 55(d) are diagrams for explaining, as an example, a manufacturing process of a light emitting device having an optical confinement layer of the third structure shown in FIG. 54(a) (part 1). [Figure 56] FIGS. 56(a) to 56(d) are diagrams for explaining, as an example, a manufacturing process of a light-emitting device having an optical confinement layer of the third structure shown in FIG. 54(a) (part 2). [Figure 57] 57(a) to 57(d) are diagrams for explaining, as an example, a manufacturing process of a light emitting device having an optical confinement layer of the third structure shown in FIG. 54(a) (part 3). [Figure 58]58(a) to 58(d) are diagrams for explaining, as an example, a manufacturing process of a light emitting device having an optical confinement layer of the third structure shown in FIG. 54(a) (part 4). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] [Description of the embodiments of the present disclosure] First, the contents of the embodiments of the present disclosure will be individually listed and described.

[0012] (1) As one aspect of this embodiment, the optical device of the present disclosure includes a UC layer (upconversion layer), a first optical confinement layer (reflective layer or single layer), a second optical confinement layer (reflective layer or single layer), and a resonant mode forming layer. The UC layer includes an upconversion material that receives excitation light included in a first wavelength range and outputs light in a second wavelength range shorter than the first wavelength range. The first optical confinement layer has an optical reflectance property that reflects at least a part of the light in the second wavelength range. The second optical confinement layer has an optical reflectance property that reflects a part of the light in the second wavelength range and transmits the remainder. In addition, the second optical confinement layer is disposed so that the UC layer is located between the first optical confinement layer and the second optical confinement layer. That is, the second optical confinement layer is disposed on the opposite side of the first optical confinement layer with respect to the UC layer. The resonant mode forming layer is provided between the first optical confinement layer and the UC layer, or between the second optical confinement layer and the UC layer. The resonance mode layer includes a base layer and a plurality of modified refractive index areas that have a refractive index different from that of the base layer and are two-dimensionally distributed on a reference plane perpendicular to a thickness direction of the resonance mode forming layer, whereby the resonance mode forming layer forms a resonance mode of light in a second wavelength range along the reference plane.

[0013] An upconversion material is a material that has the effect of converting low-energy light with a long wavelength, such as near-infrared light, into high-energy light with a shorter wavelength. In this optical device, when the UC layer receives excitation light in a first wavelength range (for example, near-infrared range), light in a second wavelength range (for example, visible range such as red range, green range, or blue range) shorter than the first wavelength range is generated in the UC layer. The light in the second wavelength range is confined between the first light confinement layer and the second light confinement layer and is diffracted by the resonance mode forming layer. In the resonance mode forming layer, a resonance mode is formed along a predetermined direction (in-plane direction) on a reference perpendicular to the thickness direction of the resonance mode forming layer, and a laser light of a mode according to the arrangement of the multiple modified refractive index areas is generated. The laser light travels in the thickness direction of the resonance mode forming layer, passes through the second light reflecting layer, and is output to the outside of the optical device.

[0014] In this way, the optical device described above can output laser light with a relatively short wavelength based on pump light with a relatively long wavelength. In addition, there is no need to use a nitride semiconductor such as GaN for the resonant mode forming layer, and there is a high degree of freedom in the selection of materials for the resonant mode forming layer. Therefore, it is easy to increase the optical confinement coefficient of the resonant mode forming layer. Therefore, the optical device of the present disclosure can provide a practical photonic crystal surface emitting laser or phase-modulated light emitting element (Static-iPMSEL) that can output light in a relatively short wavelength range, such as the visible range.

[0015] Each of the first and second optical confinement layers may be a light reflecting layer having a multi-layered structure such as a dielectric multi-layered film, or may be a single layer made of a single material having a substantially uniform refractive index distribution at least along the thickness direction of the optical confinement layer (the direction from the first optical confinement layer to the second optical confinement layer) and a refractive index lower than that of the UC layer. A resonant mode forming layer may be embedded in the interior or surface region of the optical confinement layer having a single-layer structure. Specifically, when the second optical confinement layer includes a resonant mode forming layer, as one embodiment of the present disclosure, the second optical confinement layer has a single-layer structure in which a part of the second optical confinement layer including a layer surface facing the UC layer constitutes a basic layer, and a plurality of recesses for defining a plurality of modified refractive index areas are provided on the layer surface.

[0016] (2) As an aspect of the present embodiment in which the second optical confinement layer has a single-layer structure in which the resonant mode forming layer is embedded, the optical device also includes a UC layer, a first optical confinement layer (single layer), a second optical confinement layer (reflective layer or single layer), and a resonant mode forming layer, as in the above aspect. The UC layer receives excitation light in a first wavelength range and outputs light in a second wavelength range shorter than the first wavelength range. The first optical confinement layer has an optical reflectance characteristic of reflecting at least a part of the light in the second wavelength range. The second optical confinement layer has an optical reflectance characteristic of reflecting a part of the light in the second wavelength range while transmitting the remainder. The second optical confinement layer has a single-layer structure in which the UC layer is disposed between the first optical confinement layer and the second optical confinement layer, and in which a resonant mode of light in the second wavelength range is formed. The resonant mode forming layer forms a resonant mode of light in the second wavelength range. Specifically, the resonant mode forming layer is provided on the side where the layer surface of the second optical confinement layer facing the UC layer is located, and includes a basic layer that constitutes a part of the second optical confinement layer, and a plurality of modified refractive index regions that are defined by a plurality of recesses distributed two-dimensionally on the layer surface of the second optical confinement layer and have a refractive index different from the refractive index of the basic layer.

[0017] (3) As an embodiment of the present disclosure, the resonant mode forming layer may be a PC layer (photonic crystal layer) in which a plurality of modified refractive index areas are periodically arranged. In this case, the light in the second wavelength range output from the UC layer is diffracted by the PC layer while being confined between the first light confinement layer and the second light confinement layer. In the PC layer, a resonant mode is formed along a predetermined direction (in-plane direction) on a reference plane perpendicular to the thickness direction of the PC layer, and light is oscillated at a wavelength according to the arrangement period of the plurality of modified refractive index areas, generating laser light. For example, in a square lattice crystal, when the arrangement period is set to the length of one wavelength of light, a part of the laser light is diffracted in the thickness direction of the PC layer, passes through the second light reflecting layer, and is output to the outside of the optical device. In addition to the PC layer, a phase modulation layer or the like can be applied to the resonant mode forming layer.

[0018] (4) The optical device may be an optical device (e.g., a phase-modulating light-emitting element) that outputs an optical image. That is, as one aspect of the present disclosure, in a virtual square lattice set on a reference plane on which a plurality of modified refractive index areas are to be formed, each of the plurality of modified refractive index areas may be arranged such that, with its center of gravity being separated from a corresponding lattice point among the lattice points of the virtual square lattice, a line segment connecting the center of gravity and the corresponding lattice point has a rotation angle according to the optical image with respect to the virtual square lattice. In this case, the light in the second wavelength range output from the UC layer is diffracted by the resonant mode forming layer while being confined between the first light confinement layer and the second light confinement layer. In the resonant mode forming layer, the center of gravity of the plurality of modified refractive index areas has a rotation angle set for each modified refractive index area around the lattice point of the virtual square lattice. In this case, compared to the case where the centers of gravity of the multiple modified refractive index areas are located on the lattice points of a square lattice, the light intensity of the light output in the thickness direction of the resonance mode forming layer (in other words, the direction perpendicular to the light output surface of the optical device), i.e., the zeroth order light, decreases, and the light intensity of the higher order light output in a direction inclined relative to that direction, for example, +1st order light and -1st order light, increases. Furthermore, by individually setting the rotation angle of the center of gravity of each modified refractive index area around the lattice point according to the optical image, it is possible to modulate the phase of light independently for each modified refractive index area, and output an optical image of any shape in the second wavelength range.

[0019] (5) The optical device may be an optical device (e.g., a phase-modulated light-emitting element) that outputs an optical image. In one aspect of the present disclosure, in a virtual square lattice set on a reference surface on which a plurality of modified refractive index areas are to be formed, the center of gravity of each of the plurality of modified refractive index areas may be located on a straight line that passes through a corresponding lattice point among the lattice points of the virtual square lattice and is inclined with respect to the square lattice, and the distance between the center of gravity and the corresponding lattice point may be set individually according to the optical image. The light in the second wavelength range output from the UC layer is diffracted by the resonant mode forming layer while being confined between the first light confinement layer and the second light confinement layer. In the resonant mode forming layer, the centers of gravity of the plurality of modified refractive index areas are arranged on a straight line that passes through a lattice point of the virtual square lattice and is inclined with respect to the square lattice. Even in such a case, the light intensity of the light (0th order light) output in a direction perpendicular to the light output surface decreases, and the light intensity of the higher order light, such as +1st order light and -1st order light, output in a direction inclined with respect to that direction increases. Furthermore, by individually setting the distance between the center of gravity of each modified refractive index area and the corresponding lattice point according to the optical image, the phase of the light can be modulated independently for each modified refractive index area, and an optical image of any shape in the second wavelength range can be output.

[0020] (6) As an embodiment of the present disclosure, a diffractive optical element (DOE) may be further provided on the opposite side of the UC layer with respect to the second optical confinement layer (i.e., the second optical confinement layer is located between the diffractive optical element and the UC layer). In this case, by forming a phase distribution based on an optical image of an arbitrary shape in advance in the diffractive optical element, the laser light in the second wavelength range that has passed through (output from) the second optical confinement layer can be converted into an optical image of an arbitrary shape. Therefore, an optical image of an arbitrary shape in the second wavelength range can be output.

[0021] (7) As an embodiment of the present disclosure, a spatial light modulator may be further provided on the opposite side of the UC layer with respect to the second optical confinement layer (i.e., the second optical confinement layer is located between the spatial light modulator and the UC layer). In this case, by presenting a phase pattern based on an optical image of an arbitrary shape in the spatial light modulator, the laser light of the second wavelength range that is output after passing through the second optical confinement layer can be converted into an optical image of an arbitrary shape. Therefore, an optical image of an arbitrary shape in the second wavelength range can be output.

[0022] (8) As an embodiment of the present disclosure, the optical device may further include a dichroic mirror disposed on the opposite side of the UC layer with respect to the second optical confinement layer (i.e., the second optical confinement layer is located between the dichroic mirror and the UC layer). The dichroic mirror has a higher optical transmittance in the second wavelength range than the first wavelength range. In this case, even if a part of the excitation light passes through the second optical confinement layer without being absorbed by the UC layer and mixes with the light of the second wavelength range, the excitation light is less likely to pass through the dichroic mirror than the light of the second wavelength range, so that the component of the excitation light is reduced in the light after passing through the dichroic mirror. Therefore, it is possible to suppress the excitation light from being mixed into the light of the second wavelength range output from the optical device.

[0023] (9) In one embodiment of the present disclosure, the first wavelength range may be the near-infrared range, and the second wavelength range may be the visible range. As described above, light in the near-infrared range can be easily obtained by a light-emitting device that mainly includes, for example, a GaAs-based semiconductor. On the other hand, light in the visible range, particularly light in the green range to blue range, can be obtained by a light-emitting device that mainly includes, for example, a nitride semiconductor such as GaN, but due to the characteristics of the material, it is difficult to obtain practical light output characteristics with a photonic crystal surface-emitting laser or a phase-modulated light-emitting device. On the other hand, according to the optical device of the present disclosure, it is not necessary to use a nitride semiconductor such as GaN in the resonant mode forming layer, and the degree of freedom in selecting the material of the resonant mode forming layer is high. Therefore, it is possible to provide a practical photonic crystal surface-emitting laser or a phase-modulated light-emitting device that can output light in the visible range. This makes it possible to enrich color expression in the visible range.

[0024] (10) In one embodiment, the light-emitting device of the present disclosure includes an optical device having the above-described structure and an excitation light source integrated with the optical device via a first light confinement layer. With this configuration, excitation light output from the excitation light source can be supplied to the UC layer. With this light-emitting device, it is possible to provide a practical surface-emitting self-luminous device capable of outputting light in a relatively short wavelength range, such as the visible range.

[0025] (11) As an aspect of the present disclosure, the pumping light source may include a photonic crystal surface-emitting laser disposed on the opposite side of the UC layer with respect to the first optical confinement layer (i.e., the first optical confinement layer is disposed between the UC layer and the photonic crystal surface-emitting laser). In addition, the optical transmittance of the first optical confinement layer in the first wavelength range is preferably greater than the optical transmittance of the first optical confinement layer in the second wavelength range. In this case, the pumping light output from the photonic crystal surface-emitting laser passes through the first optical confinement layer and is supplied to the UC layer. Therefore, the light in the second wavelength range can be suitably output from the optical device. In addition, according to this light-emitting device, the optical device is formed on the light output surface of the photonic crystal surface-emitting laser with the same stacking direction, so that a light-emitting device in which the optical device and the pumping light source are integrated can be easily manufactured.

[0026] (12) As an aspect of the present disclosure, in a photonic crystal surface-emitting laser or a phase-modulated light-emitting element, a PC layer larger than the light-emitting region may be provided to suppress reflection at the region end. In this case, in the above-mentioned light-emitting device, the area of ​​the PC layer of the photonic crystal surface-emitting laser viewed from the stacking direction of the photonic crystal surface-emitting laser is larger than the area of ​​the UC layer viewed from the stacking direction of the optical device. Furthermore, in this case, as an aspect of the present disclosure, the photonic crystal surface-emitting laser includes a semiconductor substrate, a semiconductor stack, a first electrode, and a second electrode. The semiconductor substrate has a main surface and a back surface. The semiconductor stack is provided on the main surface of the semiconductor substrate and includes an active layer and a PC layer. The first electrode is made of a metal material and is provided on the back surface of the semiconductor substrate. The second electrode is provided on the semiconductor stack. The first electrode may have an opening for passing the excitation light, and at least a part of the first light confinement layer may be disposed within the opening of the first electrode. Since the first electrode provided on the back surface of the semiconductor substrate is made of metal, a larger current can be supplied compared to a transparent electrode, and the emission intensity of the photonic crystal surface-emitting laser can be increased. Furthermore, since at least a part of the first optical confinement layer is disposed within the opening of the first electrode, the first optical confinement layer and the back surface of the semiconductor substrate can be brought closer to each other. Furthermore, in the light-emitting device of the present disclosure, the active layer, the PC layer, and the phase modulation layer may each be sandwiched between cladding layers having a lower refractive index. This makes it possible to effectively confine light in the active layer and the PC layer.

[0027] (13) As an aspect of the present disclosure, the excitation light source may include a plurality of photonic crystal surface-emitting lasers arranged on the opposite side of the UC layer with respect to the first optical confinement layer (i.e., the first optical confinement layer is arranged between the UC layer and the plurality of photonic crystal surface-emitting lasers). The plurality of photonic crystal surface-emitting lasers are arranged one-dimensionally or two-dimensionally along the surface of the first optical confinement layer. The optical transmittance of the first optical confinement layer in the first wavelength range is greater than the optical transmittance of the first optical confinement layer in the second wavelength range. In this case, the excitation light output from the plurality of photonic crystal surface-emitting lasers passes through the first optical confinement layer and is supplied to the UC layer, so that light in the second wavelength range can be suitably output from the optical device. In addition, according to this light-emitting device, the excitation light is generated using a plurality of photonic crystal surface-emitting lasers arranged in a one-dimensional or two-dimensional manner, so that the area of ​​the optical device viewed from the light output direction can be made larger. Therefore, for example, the area of ​​the optical image output from the light-emitting device can be made larger.

[0028] (14) As an aspect of the present disclosure, in a configuration in which a plurality of photonic crystal surface-emitting lasers are provided, each photonic crystal surface-emitting laser may include a semiconductor substrate, a semiconductor laminate, a first electrode, and a second electrode. The semiconductor substrate has a main surface and a back surface. The semiconductor laminate is provided on the main surface of the semiconductor substrate and includes an active layer and a PC. The first electrode is provided on the back surface of the semiconductor substrate and is made of a transparent conductive film. The second electrode is provided on the semiconductor laminate. Moreover, the excitation light passes through the first electrode and reaches the first light confinement layer. In this case, the current density distribution supplied to the active layer of the photonic crystal surface-emitting laser can be made closer to uniform compared to the case in which the first electrode is a metal electrode having an opening. Therefore, the light intensity distribution in a plane perpendicular to the output direction of the excitation light can be made closer to uniform, and the uniformity of the excitation of the UC layer can be improved.

[0029] (15) As an aspect of the present disclosure, the area of ​​the PC layer of the photonic crystal surface-emitting laser as viewed from the stacking direction of the photonic crystal surface-emitting laser may be smaller than the area of ​​the UC layer as viewed from the stacking direction of the optical device. Furthermore, in this case, as an aspect of the present disclosure, the photonic crystal surface-emitting laser includes a semiconductor substrate, a semiconductor laminate, a first electrode, and a second electrode. The semiconductor substrate has a main surface and a back surface. The semiconductor laminate is provided on the main surface of the semiconductor substrate and includes an active layer and a PC layer. The first electrode is provided on an area of ​​the main surface of the semiconductor substrate that is exposed without being covered by the semiconductor laminate. The second electrode is provided on the semiconductor laminate. In this configuration, the first light confinement layer is disposed on the back surface of the semiconductor substrate. In this manner, the first electrode and the second electrode are both disposed on the main surface side of the semiconductor substrate, which facilitates the mounting operation of the light-emitting device of the present disclosure on the submount. As one aspect of the present disclosure, the pumping light source may include a plurality of photonic crystal surface-emitting lasers arranged on the opposite side of the UC layer with respect to the first optical confinement layer (i.e., the first optical confinement layer is arranged between the UC layer and the plurality of photonic crystal surface-emitting lasers). The plurality of photonic crystal surface-emitting lasers are arranged one-dimensionally or two-dimensionally along the surface of the first optical confinement layer. The optical transmittance of the first optical confinement layer in the first wavelength range is greater than the optical transmittance of the first optical confinement layer in the second wavelength range.

[0030] As described above, each aspect listed in the [Description of the embodiments of the present disclosure] section is applicable to each of the remaining aspects or to all combinations of these remaining aspects.

[0031] [Details of the embodiment of the present disclosure] Hereinafter, specific structures of the optical device and the light-emitting device of the present disclosure will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to these examples, but is indicated by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims. In addition, in the description of the drawings, the same elements are given the same reference numerals, and duplicated descriptions are omitted.

[0032] (First embodiment) FIG. 1 is a cross-sectional view showing a configuration of a light-emitting device 1A according to a first embodiment of the present disclosure. The light-emitting device 1A includes an optical device 10A and an excitation light source 20A. The excitation light source 20A generates excitation light included in a first wavelength range. The first wavelength range is, for example, a near-infrared range (0.75 μm to 1.4 μm). In one example, the wavelength of the excitation light is 940 nm. Each of the optical device 10A and the excitation light source 20A according to the first embodiment is a photonic crystal surface emitting laser (PCSEL). The optical device 10A receives excitation light from the excitation light source 20A and outputs light Lout in a second wavelength range shorter than the first wavelength range. The second wavelength range is included in the visible light range, for example, a red range (620 nm to 750 nm), a green range (495 nm to 570 nm), or a blue range (450 nm to 495 nm). The optical device 10A and the excitation light source 20A will be specifically described below. For ease of understanding, an XYZ orthogonal coordinate system is defined in the drawings as necessary. The light-emitting device 1A forms a standing wave along a predetermined direction (in-plane direction) on a reference plane parallel to the XY plane, and outputs light Lout in a direction (Z direction) perpendicular to the light output surface.

[0033] The optical device 10A of the first embodiment includes a UC layer 11 (upconversion layer), a PC layer 12A (photonic crystal layer), a first light reflecting layer 13 as a first light confinement layer, and a second light reflecting layer 14 as a second light confinement layer. These layers are parallel to the XY plane and are stacked along the Z direction (corresponding to the thickness direction of each layer). The light Lout passes through the second light reflecting layer 14 (is output from the second light reflecting layer 14). Details of the upconversion material are described in, for example, the above-mentioned Non-Patent Document 1.

[0034] According to the above-mentioned Non-Patent Document 1, the UC layer 11 is a layer containing an upconversion material. The UC layer 11 may be composed of only the upconversion material, or the upconversion material may be dispersed inside the resin. The upconversion material is a material that receives excitation light included in a first wavelength range and outputs light in a second wavelength range. Unlike a normal luminescence phenomenon in which a material is excited by a high-energy (short-wavelength) photon to generate a low-energy (long-wavelength) photon, upconversion is a phenomenon in which a material is excited by a low-energy (long-wavelength) photon to generate a high-energy (short-wavelength) photon. In addition, as a phenomenon in which light of a certain wavelength generates light of a shorter wavelength, there are two-photon absorption-based luminescence and second harmonic generation, but upconversion is also different from these.

[0035] For upconversion, lanthanide ions (Er 3+ , Ho 3+ , Tm 3+ There are two types of upconversion: upconversion by triplet-triplet annihilation (TTA), and upconversion based on triplet-triplet annihilation (TTA). According to the above-mentioned Non-Patent Document 1, most of the currently known upconversion materials contain lanthanide ions as sensitizers and luminescent agents. This is because the f electrons of lanthanide ions have a large energy level and many of the f electrons have a long lifetime (~ms). The mechanisms of the lanthanide upconversion process are classified into three main processes: absorption in the excited state, energy transfer upconversion, and photon avalanche.

[0036] As the main raw material (upconversion material) of the resin (ultraviolet curable resin) applicable to the UC layer 11, the photopolymerizable monomer is preferably at least one selected from the group consisting of acrylate and methacrylate. The selected photopolymerizable monomer may be either a monofunctional monomer or a polyfunctional monomer. Examples of the monofunctional monomer include carboxyethyl acrylate, isobornyl acrylate, octyl acrylate, lauryl acrylate, stearyl acrylate, nonylphenoxy polyethylene glycol acrylate, dicyclopentenyl acrylate, dicyclopentenyloxyethyl acrylate, dicyclopentanyl acrylate, benzyl acrylate, phenoxyethyl acrylate, dicyclopentenyloxyethyl methacrylate, dicyclopentanyl methacrylate, benzyl methacrylate, octyl methacrylate, and 2-ethylhexyl-diglycol acrylate. Examples of the polyfunctional monomer include diethylene glycol acrylate, 1,4-butanediol diacrylate, 1,6-hexanediol acrylate, 1,9-nonanediol diacrylate, polypropylene glycol diacrylate, EO-modified bisphenol A diacrylate, dicyclopentanyl diacrylate, neopentyl glycol-modified trimethylolpropane diacrylate, 4,4'-diacryloyloxystilbene, diethylene glycol methacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol methacrylate, 1,9-nonanediol dimethacrylate, dicyclopentanyl dimethacrylate, neopentyl glycol dimethacrylate, EO-modified bisphenol A dimethacrylate, tris(2-acryloyloxyethyl)isocyanurate, and caprolactone-modified dipentaerythritol hexaacrylate.

[0037] The PC layer 12A, which is a diffraction grating layer, functions as a resonant mode forming layer in the first embodiment. The PC layer 12A is provided between the first light reflecting layer 13 or the second light reflecting layer 14 and the UC layer 11 (between the first light reflecting layer 13 and the UC layer 11 in the illustrated example). In the illustrated example, the PC layer 12A is adjacent to the UC layer 11.

[0038] The PC layer 12A includes a base layer 12a and a plurality of modified refractive index areas 12b. The base layer 12a is made of a first refractive index medium. The plurality of modified refractive index areas 12b are made of a second refractive index medium having a refractive index different from that of the first refractive index medium, and are present in the base layer 12a. The base layer 12a may be made of an inorganic material such as SiO2, or an organic material such as a resin. The material of the base layer 12a may be insulating, semiconducting, or conductive. The modified refractive index areas 12b may be holes, or may have a structure in which a solid medium is embedded in the holes. When the modified refractive index areas 12b are holes, the PC layer 12A may further include a layer on the base layer 12a to cover the holes. The material of this layer may be the same as or different from the material of the base layer 12a.

[0039] The multiple modified refractive index areas 12b are two-dimensionally and periodically arranged in a plane (parallel to the XY plane) perpendicular to the thickness direction (Z direction) of the PC layer 12A. When the effective refractive index (equivalent refractive index) is n1, the wavelength λ1 (=a1×n1, a1 is the lattice interval) selected by the PC layer 12A is included in the emission wavelength range (second wavelength range) of the UC layer 11. The PC layer 12A forms a resonance mode of light with a wavelength λ1 on a plane perpendicular to the thickness direction of the PC layer 12A. The arrangement period of the multiple modified refractive index areas 12b is set so that the light with the wavelength λ1 performs Γ-point oscillation or M-point oscillation. Therefore, the PC layer 12A can select the wavelength λ1 from the emission wavelengths of the UC layer 11 and output it to the outside.

[0040] FIG. 2 is a plan view of the PC layer 12A. Here, a virtual square lattice is set on the PC layer 12A on a plane (reference plane) parallel to the XY plane. One side of the square lattice is parallel to the X axis, and the other side is parallel to the Y axis. In this case, a square unitary constituent region R centered on a lattice point O of the square lattice can be set two-dimensionally over multiple columns (x=0,1,2,3) along the X axis and multiple rows (y=0,1,2) along the Y axis. The unitary constituent region R is a region surrounded by a straight line that divides the lattice points of the virtual square lattice into two equal parts. A fixed number of one or more than two modified refractive index regions 12b are provided in each unitary constituent region R. The planar shape of the modified refractive index region 12b is, for example, a circular shape. In the unitary constituent region R(x,y), the center of gravity G of the modified refractive index region 12b overlaps (coincides with) the lattice point O(x,y). The periodic structure of the multiple modified refractive index areas 12b is not limited to this, and for example, a triangular lattice may be set instead of a square lattice.

[0041] Although FIG. 2 shows an example in which the shape of the modified refractive index area 12b on the reference plane is circular, the modified refractive index area 12b may have a shape other than a circle. For example, the shape of the modified refractive index area 12b may have mirror symmetry (line symmetry). Here, mirror symmetry (line symmetry) means that the planar shape of the modified refractive index area 12b located on one side of a certain straight line on the reference plane parallel to the XY plane and the planar shape of the modified refractive index area 12b located on the other side of the straight line can be mirror symmetric (line symmetric) with each other. As an example of a shape having mirror symmetry (line symmetry), for example, a perfect circle is shown in FIG. 3(a), a square is shown in FIG. 3(b), a regular hexagon is shown in FIG. 3(c), a regular octagon is shown in FIG. 3(d), a regular hexagon is shown in FIG. 3(e), a rectangle is shown in FIG. 3(f), and an ellipse is shown in FIG. 3(g).

[0042] The shape of the modified refractive index area 12b defined on a reference plane parallel to the XY plane may not have 180° rotational symmetry. As examples of such shapes, for example, FIG. 4(a) shows an equilateral triangle, FIG. 4(b) shows an isosceles right triangle, FIG. 4(c) shows a shape in which parts of two circles or ellipses overlap, FIG. 4(d) shows an egg shape (a shape in which an ellipse is deformed so that the dimension in the minor axis direction near one end along the major axis is smaller than the dimension in the minor axis direction near the other end), FIG. 4(e) shows a teardrop shape (a shape in which one end along the major axis of an ellipse is deformed into a pointed end protruding along the major axis), FIG. 4(f) shows an isosceles triangle, FIG. 4(g) shows an arrow shape (a shape in which one side of a rectangle is recessed into a triangular shape and the opposing side is pointed into a triangular shape), FIG. 4(h) shows a trapezoid, FIG. 4(i) shows a pentagon, FIG. 4(j) shows a shape in which parts of two rectangles overlap, and FIG. 4(k) shows a shape in which parts of two rectangles overlap and do not have mirror symmetry. In this way, since the shape of the modified refractive index area 12b does not have 180° rotational symmetry, it is possible to obtain a higher optical output.

[0043] 5(a) to 5(k) are plan views showing another example of the shape of the modified refractive index area defined on a reference plane parallel to the XY plane. In this example, a plurality of modified refractive index areas 12c are further provided in addition to the plurality of modified refractive index areas 12b. Each modified refractive index area 12c is made of a second refractive index medium having a refractive index different from that of the first refractive index medium of the base layer 12a. The modified refractive index areas 12c may be holes, as in the case of the modified refractive index area 12b, or may be configured by filling the holes with a solid medium. The modified refractive index areas 12c are provided in one-to-one correspondence with the modified refractive index areas 12b. The center of gravity G of the modified refractive index areas 12b and 12c combined is located on a lattice point of the unitary constituent area R that constitutes a virtual square lattice. Note that both modified refractive index areas 12b and 12c are included within the range of the unitary constituent area R that constitutes a virtual square lattice.

[0044] The plane shape of the modified refractive index area 12c is, for example, circular, but may have various shapes, similar to the modified refractive index area 12b. FIG. 5(a) to FIG. 5(k) show examples of the shapes and relative relationships of the modified refractive index areas 12b and 12c in the XY plane. FIG. 5(a) and FIG. 5(b) show a form in which the modified refractive index areas 12b and 12c have the same shaped figures. FIG. 5(c) and FIG. 5(d) show a form in which the modified refractive index areas 12b and 12c have the same shaped figures and overlap each other partially. FIG. 5(e) shows a form in which the modified refractive index areas 12b and 12c have the same shaped figures and are rotated relative to each other. FIG. 5(f) shows a form in which the modified refractive index areas 12b and 12c have different shaped figures. FIG. 5(g) shows a form in which the modified refractive index areas 12b and 12c have different shaped figures and are rotated relative to each other.

[0045] 5(h) to 5(k), the modified refractive index area 12b may be configured to include two areas 12b1 and 12b2 spaced apart from each other. The distance between the center of gravity of the areas 12b1 and 12b2 (corresponding to the center of gravity of a single modified refractive index area 12b) and the center of gravity of the modified refractive index area 12c may be set arbitrarily within the unitary constituent area R. In this case, the areas 12b1 and 12b2 and the modified refractive index area 12c may have the same shape as each other, as shown in FIG. 5(h). Alternatively, two of the areas 12b1 and 12b2 and the modified refractive index area 12c may have different shapes from the others, as shown in FIG. 5(i). In addition, as shown in FIG. 5(j), in addition to the angle of the straight line connecting the areas 12b1 and 12b2 with respect to the X-axis, the angle of the modified refractive index area 12c with respect to the X-axis may be set arbitrarily within the unitary constituent area R. Furthermore, as shown in FIG. 5(k), the angle of the line connecting areas 12b1 and 12b2 with respect to the X-axis may be set arbitrarily within unitary constituent area R while areas 12b1, 12b2 and modified refractive index area 12c maintain the same relative angle with each other.

[0046] In addition, a plurality of modified refractive index areas 12b may be provided for each unitary constituent region R. Here, the unitary constituent region R refers to a region with the smallest area among the regions surrounded by the perpendicular bisectors of the lattice points of a certain unitary constituent region R and the lattice points of other unitary constituent regions arranged periodically, and corresponds to a Wigner-Seitz cell in solid state physics. In this case, the plurality of modified refractive index areas 12b included in one unitary constituent region R may have figures of the same shape, and the centers of gravity of each may be separated from each other. In addition, the shape of the modified refractive index areas 12b may be the same between the unitary constituent regions R, and the modified refractive index areas 12b may be superimposed on each other between the unitary constituent regions R by a translation operation, or a translation operation and a rotation operation. In this case, the fluctuation of the photonic band structure is reduced, and a spectrum with a narrow line width can be obtained. Alternatively, the shape of the modified refractive index area does not necessarily have to be the same between the unitary constituent regions R, and the shapes of the adjacent unitary constituent regions R may be different from each other.

[0047] In the above-mentioned structure, the modified refractive index area 12b is a hole, but the modified refractive index area 12b may have an inorganic material having a refractive index different from that of the base layer 12a embedded in the hole. In this case, for example, after the hole in the base layer 12a is formed by etching, the inorganic material may be embedded in the hole using a chemical vapor deposition method or the like. Also, after the modified refractive index area 12b is formed by embedding an inorganic material in the hole in the base layer 12a, the same inorganic material as that of the modified refractive index area 12b may be deposited thereon. Note that, when the modified refractive index area 12b is a hole, the hole may be filled with an inert gas such as argon or nitrogen, or a gas such as hydrogen or air.

[0048] Referring again to FIG. 1, the first light reflecting layer 13 has a light reflecting property of reflecting at least a part of light in a second wavelength range including the emission wavelength of the UC layer 11. The first light reflecting layer 13 is located on the excitation light source 20A side with respect to the UC layer 11 and the PC layer 12A. The first light reflecting layer 13 is, for example, composed of a dielectric multilayer film (multilayer laminate structure). The first light reflecting layer 13 of the first embodiment is a dichroic mirror, which reflects light in a second wavelength range including the emission wavelength of the UC layer 11 and transmits light in a first wavelength range including the wavelength of the excitation light output from the excitation light source 20A. In the illustrated example, the first light reflecting layer 13 is adjacent to the PC layer 12A. Note that, without being limited to the illustrated example, another layer or an air gap may be provided between the first light reflecting layer 13 and the PC layer 12A (or the UC layer 11 when the UC layer 11 is between the first light reflecting layer 13 and the PC layer 12A).

[0049] The second light reflecting layer 14 has a light reflecting property of reflecting a part of the light of the emission wavelength (second wavelength region) of the UC layer 11 while transmitting the remaining part. The second light reflecting layer 14 is located on the opposite side of the excitation light source 20A with respect to the UC layer 11 and the PC layer 12A, and sandwiches the UC layer 11 and the PC layer 12A between the first light reflecting layer 13. The second light reflecting layer 14 is composed of, for example, a dielectric multilayer film (multilayer laminated structure). In the example of FIG. 1, the second light reflecting layer 14 is adjacent to the UC layer 11. Note that, without being limited to the example of FIG. 1, another layer or an air gap may be provided between the second light reflecting layer 14 and the UC layer 11 (or the PC layer 12A when the PC layer 12A is between the UC layer 11 and the second light reflecting layer 14).

[0050] The light emitting device 1A of the first embodiment further includes a substrate 15 and a dichroic mirror 16. The substrate 15 is made of a material that transmits light of the emission wavelength (second wavelength range) of the UC layer 11, for example, a quartz plate. A second light reflecting layer 14 is formed on one surface of the substrate 15, and a dichroic mirror 16 is formed on the other surface. The dichroic mirror 16 is disposed on the opposite side of the UC layer 11 with respect to the second light reflecting layer 14. The dichroic mirror 16 reflects light of a first wavelength range including the wavelength of the excitation light, and transmits light of a second wavelength range including the emission wavelength of the UC layer 11. In other words, the light transmittance of the dichroic mirror 16 in the second wavelength range is greater than the light transmittance in the first wavelength range. The dichroic mirror 16 is formed of, for example, a dielectric multilayer film.

[0051] The dielectric multilayer film constituting the first light reflecting layer 13, the second light reflecting layer 14, and the dichroic mirror 16 is formed by alternately laminating a first layer having a first refractive index and a second layer having a second refractive index different from the first refractive index. The wavelength-light reflection (or transmission) characteristics of the dielectric multilayer film are determined by the refractive index difference between the first refractive index and the second refractive index, the thickness of the first and second layers, and the number of layers of the first and second layers. Examples of materials that can be used for the first and second layers include titanium oxide (TiO2), silicon dioxide (SiO2), silicon monoxide (SiO), niobium oxide (Nb2O5), tantalum pentoxide (Ta2O5), magnesium fluoride (MgF2), titanium oxide (TiO2), aluminum oxide (Al2O3), cerium oxide (CeO2), indium oxide (In2O3), and zirconium oxide (ZrO2).

[0052] The UC layer 11 has a thickness of, for example, 0.1 μm or more and 50 μm or less. The PC layer 12A has a thickness of, for example, 70 nm. The first light reflecting layer 13 has a thickness of, for example, 10 μm. The second light reflecting layer 14 has a thickness of, for example, 10 μm.

[0053] Next, the excitation light source 20A of the first embodiment will be described. The excitation light source 20A is integrated with the optical device 10A via the first light reflecting layer 13, and supplies excitation light to the UC layer 11. As described above, the excitation light source 20A of the first embodiment is a PCSEL, and is disposed at a position where the first light reflecting layer 13 is sandwiched between the excitation light source 20A and the UC layer 11.

[0054] The excitation light source 20A includes a semiconductor substrate 21 having a primary surface 21a and a rear surface 21b, a semiconductor laminate provided on the primary surface 21a of the semiconductor substrate 21, a first electrode 27 (n electrode), and a second electrode 28 (p electrode). The semiconductor laminate includes an active layer 22, a PC layer 23 (photonic crystal layer), a first cladding layer 24, a second cladding layer 25, and a contact layer 26. The first cladding layer 24 is provided on the primary surface 21a of the semiconductor substrate 21, and in one example, is in contact with the primary surface 21a of the semiconductor substrate 21. The second cladding layer 25 is provided on the first cladding layer 24. The active layer 22 is provided between the first cladding layer 24 and the second cladding layer 25. The energy band gap of the first cladding layer 24 and the energy band gap of the second cladding layer 25 are wider than the energy band gap of the active layer 22. The PC layer 23 is provided between the first cladding layer 24 and the active layer 22, or between the active layer 22 and the second cladding layer 25. In the example of Fig. 1, the PC layer 23 is provided between the active layer 22 and the second cladding layer 25, and is in contact with the second cladding layer 25 and the active layer 22. The contact layer 26 is provided on the second cladding layer 25. The thickness directions of the semiconductor substrate 21, the active layer 22, the PC layer 23, the first cladding layer 24, the second cladding layer 25, and the contact layer 26 coincide with the Z direction.

[0055] If necessary, an optical guide layer for adjusting the light distribution may be provided at least one of between the first cladding layer 24 and the active layer 22 and between the active layer 22 and the second cladding layer 25. The optical guide layer may include a carrier barrier layer for efficiently confining carriers in the active layer 22. When the optical guide layer is provided between the active layer 22 and the second cladding layer 25, the PC layer 23 is provided between the second cladding layer 25 and the optical guide layer.

[0056] The PC layer 23 (diffraction grating layer) includes a base layer 23a and a plurality of modified refractive index areas 23b. The base layer 23a is a semiconductor layer made of a third refractive index medium. The plurality of modified refractive index areas 23b are made of a fourth refractive index medium having a refractive index different from that of the third refractive index medium, and are present in the base layer 23a. The plurality of modified refractive index areas 23b are two-dimensionally and periodically arranged on a reference plane (a plane parallel to the XY plane) perpendicular to the thickness direction of the PC layer 23. When the effective refractive index (equivalent refractive index) is n2, the wavelength λ2 (=a2×n2, a2 ​​is the lattice interval) selected by the PC layer 23 is included in the emission wavelength range (first wavelength region) of the active layer 22. The arrangement period of the plurality of modified refractive index areas 23b is set so that light of wavelength λ2 performs Γ-point oscillation. Therefore, the PC layer 23 is capable of diffraction in the Z direction by selecting the wavelength λ2 from the emission wavelengths of the active layer 22. The arrangement (excluding the arrangement period) and shape variations of the multiple modified refractive index areas 23b are the same as those of the above-mentioned PC layer 12A (see Figures 2, 3(a) to 3(g), 4(a) to 4(k), and 5(a) to 5(k)).

[0057] The first electrode 27 is a metal electrode provided on the back surface 21b of the semiconductor substrate 21. The first electrode 27 is in ohmic contact with the semiconductor substrate 21. When viewed along a direction perpendicular to the back surface 21b of the semiconductor substrate 21, the first electrode 27 has a rectangular frame shape having an opening 27a for passing excitation light. The back surface 21b of the semiconductor substrate 21 is exposed from the first electrode 27 through the opening 27a, and the exposed portion faces the first light reflecting layer 13 of the optical device 10A. In one example, at least a part of the first light reflecting layer 13 in the thickness direction is disposed within the opening 27a and contacts the back surface 21b of the semiconductor substrate 21.

[0058] The planar shape and size of the first light reflecting layer 13 are the same as those of the UC layer 11. Meanwhile, the planar shape and size of the outer edge of the first electrode 27 are the same as those of the PC layer 23. Therefore, the area of ​​the PC layer 23 as viewed along the stacking direction (Z direction) of the excitation light source 20A is larger than the area of ​​the UC layer 11 as viewed from the stacking direction (Z direction) of the optical device 10A by at least the amount of the first electrode 27. In other words, the outline of the UC layer 11 is located inside the outline of the PC layer 23 as viewed from the Z direction.

[0059] The second electrode 28 is a metal electrode provided on the semiconductor laminate (on the contact layer 26 in the example of FIG. 1) at least in a region where the opening 27a of the first electrode 27 is projected (the central region of the semiconductor laminate). The second electrode 28 is in ohmic contact with the contact layer 26. The portion of the contact layer 26 that is not in contact with the second electrode 28 may be removed. The second electrode 28 also has a function of reflecting light generated in the active layer 22.

[0060] As an example, the semiconductor substrate 21 is a GaAs substrate, and the first cladding layer 24, the active layer 22, the PC layer 23, the second cladding layer 25, and the contact layer 26 are made of GaAs-based semiconductors. The first cladding layer 24 is an AlGaAs layer. The active layer 22 has a multiple quantum well structure (barrier layer: AlGaAs / quantum well layer: InGaAs, the number of well layers is, for example, three). The base layer 23a of the PC layer 23 is an AlGaAs layer or a GaAs layer, and the modified refractive index area 23b is an air hole. The second cladding layer 25 is an AlGaAs layer. The contact layer 26 is a GaAs layer. In this case, the thickness of the semiconductor substrate 21 is, for example, 150 μm. The thickness of the first cladding layer 24 is, for example, 2000 nm. The thickness of the active layer 22 is, for example, 140 nm. The thickness of the PC layer 23 is, for example, 300 nm. The second cladding layer 25 has a thickness of, for example, 2000 nm. The contact layer 26 has a thickness of, for example, 200 nm. Assuming that the emission wavelength is 980 nm, the first cladding layer 24 has a refractive index of, for example, about 3.11, the active layer 22 has a refractive index of, for example, about 3.49, the second cladding layer 25 has a refractive index of, for example, about 3.27, and the contact layer 26 has a refractive index of, for example, about 3.52.

[0061] The first cladding layer 24 is given the same conductivity type as the semiconductor substrate 21, and the second cladding layer 25 and the contact layer 26 are given the opposite conductivity type to that of the semiconductor substrate 21. In one example, the semiconductor substrate 21 and the first cladding layer 24 are n-type, and the second cladding layer 25 and the contact layer 26 are p-type. When the PC layer 23 is provided between the active layer 22 and the first cladding layer 24, the PC layer 23 has the same conductivity type as that of the semiconductor substrate 21. Conversely, when the PC layer 23 is provided between the active layer 22 and the second cladding layer 25, the PC layer 23 has the opposite conductivity type to that of the semiconductor substrate 21. The impurity concentration is, for example, 1×10 16 ~1×10 21 / cm 3 In intrinsic (i-type) crystals, where no impurities are intentionally added, the impurity concentration is 1×10 16 / cm 3The active layer 22 is not limited to being intrinsic (i-type) and may be doped. The impurity concentration of the PC layer 23 may be intrinsic (i-type) when it is necessary to suppress the effect of loss due to light absorption via impurity levels.

[0062] The material of the first electrode 27 is appropriately selected according to the constituent material of the semiconductor substrate 21. When the semiconductor substrate 21 is an n-type GaAs substrate, the first electrode 27 may contain, for example, a mixture of Au and Ge. In one example, the first electrode 27 has a single AuGe layer or a laminated structure of an AuGe layer and an Au layer. The material of the second electrode 28 is appropriately selected according to the constituent material of the contact layer 26. When the contact layer 26 is made of p-type GaAs, the second electrode 28 can be made of a material containing at least one of Cr, Ti, and Pt and Au, for example, and has a laminated structure of a Cr layer and an Au layer. However, the materials of the first electrode 27 and the second electrode 28 are not limited to these as long as they can realize an ohmic junction.

[0063] The light emitting device 1A of the first embodiment having the above configuration operates as follows. When a driving current is supplied between the first electrode 27 and the second electrode 28, recombination of electrons and holes occurs in the active layer 22, and light in a first wavelength range (for example, near-infrared range) is output from the active layer 22. The electrons and holes that contribute to this light emission, as well as the generated light, are efficiently distributed between the first cladding layer 24 and the second cladding layer 25. Since the light output from the active layer 22 is distributed between the first cladding layer 24 and the second cladding layer 25, it enters the inside of the PC layer 23 and forms a resonance mode in a direction along the main surface 21a of the semiconductor substrate 21 according to the lattice structure inside the PC layer 23. Then, light oscillates at a wavelength according to the arrangement period of the multiple modified refractive index areas 23b, and laser light, which is excitation light, is generated. The excitation light diffracted in the Z direction from the PC layer 23 travels in a direction perpendicular to the main surface 21a of the semiconductor substrate 21 and is either directly output from the back surface 21b through the opening 27a to the optical device 10A, or is reflected at the second electrode 28 and then output from the back surface 21b through the opening 27a to the optical device 10A.

[0064] In the optical device 10A, when the UC layer 11 receives excitation light included in a first wavelength range, light in a second wavelength range (for example, a visible range such as a red range, a green range, or a blue range) shorter than the first wavelength range is generated in the UC layer 11. This light in the second wavelength range is diffracted by the PC layer 12A while being confined between the first light reflecting layer 13 and the second light reflecting layer 14. In the PC layer 12A, a resonance mode is formed along a predetermined direction (in-plane direction) on a surface perpendicular to the thickness direction (Z direction) of the PC layer 12A, and light is oscillated at a wavelength according to the arrangement period of the multiple modified refractive index areas 12b (laser light Lout is generated). The laser light Lout travels in the thickness direction of the PC layer 12A, passes through the second light reflecting layer 14, and is output to the outside of the optical device 10A.

[0065] In this way, the optical device 10A of the first embodiment can output laser light Lout having a relatively short wavelength, such as green light or blue light, based on excitation light having a relatively long wavelength, such as near-infrared light or red light. In addition, since there is no need to use a nitride semiconductor such as GaN for the PC layer 12A and there is a high degree of freedom in the material selection of the PC layer 12A, it is easy to increase the optical confinement coefficient of the PC layer 12A. In addition, there is no need to use a high-cost GaN substrate. Therefore, according to the first embodiment, it is possible to provide the optical device 10A as a practical and low-cost PCSEL that can output light in a relatively short wavelength range, such as the visible range.

[0066] As in the first embodiment, the layer that forms the resonant mode in the optical device 10A may be a PC layer 12A in which a plurality of modified refractive index areas 12b are periodically arranged. In this case, it is possible to provide a practical PCSEL that can output light in a relatively short wavelength range, such as the visible range.

[0067] As in the first embodiment, the optical device 10A may include a dichroic mirror 16 arranged on the opposite side of the UC layer 11 with respect to the second light reflecting layer 14, the dichroic mirror 16 having a light transmittance in the second wavelength range greater than that in the first wavelength range. In this case, even if a part of the excitation light passes through the second light reflecting layer 14 without being absorbed by the UC layer 11 and mixes with the light in the second wavelength range, the excitation light passes through the dichroic mirror 16 less easily than the light in the second wavelength range, so that the component of the excitation light is reduced in the light Lout after passing through the dichroic mirror 16. Therefore, it is possible to effectively suppress the excitation light from being mixed into the light Lout in the second wavelength range output from the optical device 10A.

[0068] As in the first embodiment, the first wavelength range may be the near-infrared range, and the second wavelength range may be the visible range. Light in the near-infrared range can be easily obtained by a light-emitting element that mainly contains, for example, a GaAs-based semiconductor. On the other hand, light in the visible range, such as the green range to the blue range, can be obtained by a light-emitting element that mainly contains, for example, a nitride semiconductor such as GaN, but it is difficult to obtain practical light output characteristics with a PCSEL due to the characteristics of the material. In contrast, according to the optical device 10A of the first embodiment, it is not necessary to use a nitride semiconductor such as GaN for the PC layer 12A, and there is a high degree of freedom in selecting the material for the PC layer 12A, so that a practical PCSEL that can output light in the visible range can be provided. This makes it possible to enrich color expression in the visible range.

[0069] The light-emitting device 1A of the first embodiment includes an optical device 10A and an excitation light source 20A integrated with the optical device 10A for supplying excitation light to the UC layer 11. The light-emitting device 1A can provide a practical surface-emitting self-luminous device capable of outputting light in a relatively short wavelength range, such as the visible range.

[0070] As in the first embodiment, the excitation light source 20A includes a PCSEL disposed at a position sandwiching the first light reflecting layer 13 between the excitation light source 20A and the UC layer 11, and the light transmittance of the first light reflecting layer 13 in a first wavelength range may be greater than the light transmittance of the first light reflecting layer 13 in a second wavelength range. In this case, the excitation light output from the excitation light source 20A passes through the first light reflecting layer 13 and is supplied to the UC layer 11, so that the light Lout in the second wavelength range can be suitably output from the optical device 10A. In addition, according to this light-emitting device 1A, the optical device 10A is formed on the light output surface (the back surface 21b of the semiconductor substrate 21) of the excitation light source 20A with the same stacking direction, so that the light-emitting device 1A in which the optical device 10A and the excitation light source 20A are integrated can be easily manufactured.

[0071] As in the first embodiment, the area of ​​the PC layer 23 as viewed from the stacking direction of the excitation light source 20A may be larger than the area of ​​the UC layer 11 as viewed from the stacking direction of the optical device 10A. In the PCSEL, a photonic crystal larger than the light-emitting region may be provided to suppress reflection at the end of the region. In this case, the area of ​​the PC layer 23 of the PCSEL as viewed from the stacking direction of the PCSEL is larger than the area of ​​the UC layer 11 as viewed from the stacking direction of the optical device 10A.

[0072] As in the first embodiment, the excitation light source 20A, which is a photonic crystal surface emitting laser, may have a semiconductor substrate 21, a semiconductor laminate, a first electrode 27 made of metal, and a second electrode 28. The semiconductor laminate includes an active layer 22 and a PC layer 23 provided on a main surface 21a of the semiconductor substrate 21. The first electrode 27 is provided on a back surface 21b of the semiconductor substrate 21. The second electrode 28 is provided on the semiconductor laminate. The first electrode 27 has an opening 27a for passing the excitation light, and at least a part of the first light reflecting layer 13 in the thickness direction may be disposed within the opening 27a of the first electrode 27. Since the first electrode 27 provided on the back surface 21b of the semiconductor substrate 21 is made of metal, a larger current can be supplied compared to a transparent electrode, and as a result, the emission intensity of the excitation light source 20A can be increased. Therefore, the output intensity of the light in the second wavelength range from the UC layer 11 can be increased, and laser oscillation in the optical device 10A can be more stably performed. Furthermore, by disposing at least a portion of the first light reflecting layer 13 in the thickness direction within the opening 27a of the first electrode 27, the first light reflecting layer 13 and the rear surface 21b of the semiconductor substrate 21 can be brought closer to each other.

[0073] Here, a method for manufacturing the light emitting device 1A of the first embodiment is described. First, the first cladding layer 24, the active layer 22, and the basic layer 23a of the PC layer 23 are crystal-grown in this order on the main surface 21a of the semiconductor substrate 21, for example, by metalorganic chemical vapor deposition (MOCVD). Next, an electron beam resist is applied onto the surface of the basic layer 23a, and the modified refractive index area 23b is patterned by electron beam lithography. Then, the pattern of the electron beam resist is transferred to the basic layer 23a by, for example, inductively coupled plasma (ICP) etching, to form the PC layer 23. After the electron beam resist is removed, the second cladding layer 25 and the contact layer 26 are crystal-grown in this order on the PC layer 23, for example, by MOCVD.

[0074] Next, in order to thin the semiconductor substrate 21, the back surface 21b of the semiconductor substrate 21 is polished, and then the back surface 21b is mirror-polished. Then, a first electrode 27 having an opening 27a is formed on the back surface 21b by photolithography, vacuum deposition, and lift-off. Also, a second electrode 28 is formed on the surface of the contact layer 26 by photolithography, vacuum deposition, and lift-off. Either the first electrode 27 or the second electrode 28 may be formed first.

[0075] Furthermore, a dielectric multilayer film is formed as the first light reflecting layer 13 on the back surface 21b in the opening 27a of the first electrode 27 by, for example, vacuum deposition. Then, continuously from the formation of the first light reflecting layer 13, a base layer 12a (e.g., a SiO2 film) of the PC layer 12A is formed on the first light reflecting layer 13 by, for example, vacuum deposition. An electron beam resist is applied onto the surface of the base layer 12a, and the modified refractive index area 12b is patterned by electron beam lithography. Then, the pattern of the electron beam resist is transferred to the base layer 12a by, for example, inductively coupled plasma (ICP) etching (formation of the PC layer 12A).

[0076] Next, the first electrode 27 is exposed by photolithography and wet etching. Then, an upconversion material is applied onto the PC layer 12A by a method such as spin coating or screen printing to form the UC layer 11. After that, the semiconductor substrate 21 and each layer formed on the semiconductor substrate 21 are cut into chips by dicing.

[0077] Next, the substrate 15 is prepared, and a dielectric multilayer film is formed as the second light reflecting layer 14 on one surface of the substrate 15 by, for example, vacuum deposition. A dielectric multilayer film is formed as the dichroic mirror 16 on the other surface of the substrate 15 by, for example, vacuum deposition. The second light reflecting layer 14 and the dichroic mirror 16 may be formed in any order. Then, the second light reflecting layer 14 and the UC layer 11 are bonded together. Alternatively, the substrate 15 is fixed to the UC layer 11 so that the second light reflecting layer 14 and the UC layer 11 are adjacent to each other. Through the above steps, the light emitting device 1A of the first embodiment is manufactured.

[0078] Second embodiment In the above-mentioned first embodiment, the optical device 10A including the PC layer 12A in which the modified refractive index areas 12b are periodically arranged has been described, but the optical device of the present disclosure can include various resonance mode forming layers, not limited to the PC layer (photonic crystal layer) in which the modified refractive index areas are periodically arranged. In recent years, research has been conducted on phase-modulated light-emitting devices that output any optical image by controlling the phase spectrum and intensity spectrum of light output from a plurality of light-emitting points arranged two-dimensionally. Such phase-modulated light-emitting devices are called S-iPM (Static-integrable Phase Modulating) lasers, and output optical images of any spatial shape. The resonance mode forming layer may include a configuration used in such S-iPM lasers.

[0079] 6 is a diagram showing a cross-sectional structure of a light-emitting device 1B according to a second embodiment. The light-emitting device 1B of the second embodiment includes an optical device 10B instead of the optical device 10A of the first embodiment. The configuration of the excitation light source 20A included in the light-emitting device 1B is the same as that of the first embodiment. The optical device 10B of the second embodiment differs from the optical device 10A of the first embodiment in the configuration of the resonant mode forming layer. The optical device 10B of the second embodiment includes a phase modulation layer 12B as the resonant mode forming layer instead of the PC layer 12A of the above embodiment.

[0080] FIG. 7 is a plan view of the phase modulation layer 12B. The phase modulation layer 12B includes a base layer 12a made of a first refractive index medium and a modified refractive index area 12b made of a second refractive index medium having a refractive index different from that of the first refractive index medium. Here, a virtual square lattice is set on a reference plane parallel to the XY plane in the phase modulation layer 12B. One side of the square lattice is parallel to the X axis, and the other side is parallel to the Y axis. At this time, a square-shaped unit constituent area R centered on a lattice point O of the square lattice can be set two-dimensionally over multiple columns (x=0, 1, 2, 3) along the X axis and multiple rows (y=0, 1, 2) along the Y axis. A plurality of modified refractive index areas 12b are provided in each unit constituent area R. The planar shape of the modified refractive index area 12b can be various shapes such as a circle, as in the first embodiment described above. Within the unitary constituent region R(x, y), the center of gravity G of the modified refractive index area 12b is disposed away from the corresponding lattice point O(x, y).

[0081] As shown in FIG. 8, the position in the unit constituent region R(x,y) is defined by the s-axis parallel to the X-axis and the t-axis parallel to the Y-axis, and the intersection (origin) of the s-axis and the t-axis is the lattice point O(x,y). In the unit constituent region R(x,y), the angle between the direction from the lattice point O(x,y) toward the center of gravity G and the s-axis is φ(x,y). The x component indicates the position of the x-th lattice point O along the X-axis, and the y component indicates the position of the y-th lattice point O along the Y-axis. When the rotation angle φ(x,y) is 0°, the direction of the vector connecting the lattice point O(x,y) and the center of gravity G coincides with the positive direction of the s-axis. Also, the length of the vector connecting the lattice point O(x,y) and the center of gravity G is r(x,y). In one example, r(x,y) is constant regardless of x and y (throughout the entire phase modulation layer 12B).

[0082] As shown in FIG. 7, in the phase modulation layer 12B, the rotation angle φ of the center of gravity G of the modified refractive index area 12b around the lattice point O is set independently for each unitary constituent area R according to the desired optical image. The rotation angle φ(x, y) in the unitary constituent area R(x, y) has a specific value for each position (unitary constituent area R) determined by the values ​​of the x component and the y component, but is not necessarily expressed by a specific function. That is, the rotation angle distribution φ(x, y) is determined by extracting the phase distribution from the complex amplitude distribution obtained by performing an inverse Fourier transform on the desired optical image. When obtaining the complex amplitude distribution from the desired optical image, the reproducibility of the beam pattern is improved by applying an iterative algorithm such as the Gerchberg-Saxton (GS) method, which is generally used in calculations for generating holograms.

[0083] In the second embodiment, the light output from the UC layer 11 is confined between the first light reflecting layer 13 and the second light reflecting layer 14 and is diffracted by the phase modulation layer 12B, forming a predetermined mode according to the lattice structure inside the phase modulation layer 12B. The laser light scattered and output in the phase modulation layer 12B passes through the second light reflecting layer 14 and is output to the outside. At this time, the 0th order light is output in the thickness direction (Z direction) of the phase modulation layer 12B. In contrast, the +1st order light and the -1st order light are output in any spatial direction including the Z direction and a direction inclined with respect to the Z direction.

[0084] FIG. 9 is a diagram for explaining the relationship between the optical image obtained by focusing the output beam pattern of the optical device 10B according to the second embodiment and the rotation angle distribution φ(x, y) in the phase modulation layer 12B. The center Q of the output beam pattern is located in the Z direction from the center of the light output surface of the optical device 10B, and FIG. 9 shows four quadrants with the center Q as the origin. FIG. 9 shows an example in which an optical image is obtained in the first and third quadrants, but it is also possible to obtain images in the second and fourth quadrants or all quadrants. In this second embodiment, as shown in FIG. 9, an optical image that is point-symmetric with respect to the origin is obtained. FIG. 9 shows, as an example, a case in which the letter "A" is obtained as +1st order diffracted light in the third quadrant and a pattern obtained by rotating the letter "A" by 180 degrees as -1st order diffracted light in the first quadrant. In the case of a rotationally symmetric optical image (for example, a cross, a circle, a double circle, etc.), the images are observed overlapping each other as one optical image.

[0085] The optical image obtained by focusing the output beam pattern of the optical device 10B according to the second embodiment includes at least one of a spot, a straight line, a cross, a line drawing, a grid pattern, a photograph, a striped pattern, CG (computer graphics), and a character. In order to obtain a desired optical image, the rotation angle distribution φ(x, y) of the modified refractive index area 12b of the phase modulation layer 12B is determined by the following procedure.

[0086] First, as a first prerequisite, in an XYZ orthogonal coordinate system defined by a Z axis coinciding with the normal direction and an XY plane including mutually orthogonal X and Y axes coinciding with one surface of phase modulation layer 12B including multiple modified refractive index areas 12b, a virtual square lattice composed of M1 (an integer equal to or greater than 1) × N1 (an integer equal to or greater than 1) unit constituent regions R, each having a square shape, is set on the XY plane.

[0087] The second prerequisite is that the coordinates (ξ, η, ζ) in the XYZ Cartesian coordinate system are expressed as the length of the radius r and the inclination angle θ from the Z axis, as shown in Figure 10. tilt and the rotation angle θ from the X-axis specified on the XY plane rotand the spherical coordinates (r,θ rot ,θ tilt ) satisfies the relationships shown in the following formulas (1) to (3). rot ,θ tilt ) to coordinates (ξ, η, ζ) in the XYZ Cartesian coordinate system, and the coordinates (ξ, η, ζ) represent a designed light image on a specified plane that is set in the XYZ Cartesian coordinate system, which is real space.

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[0088] A beam pattern corresponding to an optical image output from the optical device 10B is defined by an angle θ tilt and θ rot When the set of bright points is defined as a set of bright points facing in the direction defined by the angle θ tilt and θ rot is the normalized wave number defined by the following equation (4), and is the coordinate value k on the x-axis corresponding to the x-axis. x and the normalized wave number defined by the following equation (5), which corresponds to the Y axis and is a coordinate value k on the Ky axis perpendicular to the Kx axis. y The normalized wave number means a wave number normalized with the wave number corresponding to the lattice spacing of a virtual square lattice set to 1.0. In this case, in the wave number space defined by the Kx axis and the Ky axis, a specific wave number range including a beam pattern corresponding to a light image is composed of M2 (an integer of 1 or more) × N2 (an integer of 1 or more) image regions FR each having a square shape. Note that the integer M2 does not have to match the integer M1. Similarly, the integer N2 does not have to match the integer N1. Furthermore, the formulas (4) and (5) are disclosed in, for example, the above-mentioned Non-Patent Document 2.

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[0089] The third prerequisite is that in wave number space, the coordinate component k x (an integer between 0 and M2-1) and the coordinate component k in the Ky axis direction y (an integer between 0 and N2-1) and the image region FR(k x ,k y ) to a unit constituent region R(x,y) on the XY plane specified by the coordinate component x (an integer between 0 and M1-1) in the X-axis direction and the coordinate component y (an integer between 0 and N1-1) in the Y-axis direction, the complex amplitude F(x,y) is given by the following formula (6) where j is the imaginary unit. Furthermore, when the amplitude term is A(x,y) and the phase term is P(x,y), this complex amplitude F(x,y) is defined by the following formula (7). Furthermore, as a fourth precondition, the unit constituent region R(x,y) is defined by the s-axis and t-axis which 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).

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[0090] Under the above first to fourth prerequisites, the phase modulation layer 12B is configured to satisfy the following first and second conditions. That is, the first condition is that the center of gravity G is disposed in a state separated from the lattice point O(x, y) in the unit constituent region R(x, y). The second condition is that, in a state in which the line segment length r(x, y) from the lattice point O(x, y) to the corresponding center of gravity G is set to a common value in each of the M1×N1 unit constituent regions R, the angle φ(x, y) between the line segment connecting the lattice point O(x, y) and the corresponding center of gravity G and the s-axis is φ(x,y)=C×P(x,y)+B C: proportionality constant, e.g. 180 / π B: Any constant, e.g. 0 The corresponding modified refractive index area 12b is disposed within the unit constituent area R(x, y) so as to satisfy the following relationship.

[0091] FIG. 11 is a plan view showing an example in which the refractive index structure of FIG. 7 is applied only to a specific region of the phase modulation layer. In the example shown in FIG. 11, a refractive index structure (for example, the structure of FIG. 7) for outputting a target beam pattern is formed inside a square inner region RIN. Meanwhile, in the outer region ROUT surrounding the inner region RIN, a true circular modified refractive index region whose center of gravity coincides with the lattice point position of the square lattice is arranged. The lattice interval of the virtually set square lattice is the same both inside the inner region RIN and in the outer region ROUT. In the case of this structure, there is an advantage that the occurrence of high-frequency noise (so-called window function noise) caused by a sudden change in light intensity in the periphery of the inner region RIN can be suppressed by distributing light also in the outer region ROUT. In addition, since light leakage in the in-plane direction can be suppressed, the conversion efficiency from pump light to light Lout can be increased.

[0092] As a method for obtaining the intensity distribution and phase distribution from the complex amplitude distribution obtained by the two-dimensional inverse Fourier transform, for example, the intensity (amplitude) distribution I(x, y) can be calculated by using the abs function of the numerical analysis software "MATLAB" from MathWorks, and the phase distribution P(x, y) can be calculated by using the angle function of MATLAB.

[0093] Here, points to note when calculating the rotation angle distribution φ(x, y) from the inverse Fourier transform result of the light image and determining the arrangement of each modified refractive index area 12b using a general discrete Fourier transform (or fast Fourier transform) will be described. The output beam pattern calculated from the complex amplitude distribution obtained by the inverse Fourier transform of the desired light image in FIG. 12(a) is as shown in FIG. 12(b). If the space is divided into four quadrants, A1, A2, A3, and A4, as shown in FIG. 12(a) and FIG. 12(b), a pattern in which the pattern in the first quadrant of FIG. 12(a) rotated 180 degrees and the pattern in the third quadrant of FIG. 12(a) are superimposed appears in the first quadrant of the output beam pattern in FIG. 12(b). A pattern in which the pattern in the second quadrant of FIG. 12(a) rotated 180 degrees and the pattern in the fourth quadrant of FIG. 12(a) are superimposed appears in the second quadrant of the beam pattern. In the third quadrant of the beam pattern, a pattern obtained by rotating the third quadrant of Fig. 12(a) 180 degrees and superimposing the pattern in the first quadrant of Fig. 12(a) appears. In the fourth quadrant of the beam pattern, a pattern obtained by rotating the fourth quadrant of Fig. 12(a) 180 degrees and superimposing the pattern in the second quadrant of Fig. 12(a) appears. In this case, the 180-degree rotated pattern is a pattern formed in the -1st order light component.

[0094] Therefore, if a light image before the inverse Fourier transform (original light image) having values ​​only in the first quadrant is used, the first quadrant of the original light image will appear in the third quadrant of the obtained beam pattern, and a pattern obtained by rotating the first quadrant of the original light image by 180 degrees will appear in the first quadrant of the obtained beam pattern.

[0095] 13(a) to 13(d) show examples of beam patterns (optical images) output from a GaAs-based S-iPM laser in the near-infrared wavelength band that utilizes the same principle as in the second embodiment. The centers of each of the FIGS. 13(a) to 13(d) are located in the Z direction from the center of the optical output surface of the S-iPM laser. As shown in these FIGS. 13(a) to 13(d), the S-iPM laser outputs +1st order light including a first optical image portion E1 output in a first direction inclined with respect to an axis extending from the center of the optical output surface in the Z direction, -1st order light including a second optical image portion E2 output in a second direction symmetrical with respect to the first direction with respect to the axis and rotationally symmetrical with respect to the first optical image portion E1 with respect to the axis, and 0th order light E3 traveling on the axis. This is also true for the optical device 10B of the second embodiment.

[0096] In the second embodiment, the light in the second wavelength range output from the UC layer 11 is diffracted by the phase modulation layer 12B while being confined between the first light reflecting layer 13 and the second light reflecting layer 14, and as a result, a predetermined mode is formed according to the lattice structure inside the phase modulation layer 12B. In the phase modulation layer 12B, the centers of gravity of the multiple modified refractive index areas 12b have a rotation angle φ(x, y) set for each modified refractive index area 12b around a lattice point of a virtual square lattice. In this case, compared to the case where the center G of the multiple modified refractive index areas 12b is located on the lattice point of the square lattice (see FIG. 2), the light intensity of the light output in the thickness direction of the phase modulation layer 12B (in other words, the Z direction perpendicular to the light output surface of the optical device 10B), i.e., the 0th order light, decreases, and the light intensity of the high order light output in a direction inclined with respect to that direction, for example, the +1st order light and the -1st order light, increases. Furthermore, by individually setting the rotation angle φ(x, y) of the center of gravity G of each modified refractive index area 12b around the lattice point according to the desired optical image, the phase of the light is modulated independently for each modified refractive index area 12b, and as a result, an optical image of any spatial shape can be output in the Z direction perpendicular to the light output surface and in a direction tilted relative to the Z direction. This optical image (output light Lout) passes through the second light reflecting layer 14 and the dichroic mirror 16 and is output to the outside of the optical device 10B.

[0097] In the optical device 10B of the second embodiment, similarly to the first embodiment described above, light Lout having a relatively short wavelength such as green light or blue light can be output based on excitation light having a relatively long wavelength such as near-infrared light or red light. In addition, since it is not necessary to use a nitride semiconductor such as GaN for the phase modulation layer 12B, and the degree of freedom in selecting the material of the phase modulation layer 12B is high, it is easy to increase the light confinement coefficient of the phase modulation layer 12B. Therefore, according to the second embodiment, it is possible to provide the optical device 10B as a practical phase modulation light emitting element capable of outputting a two-dimensional optical image in a relatively short wavelength range such as the visible range. The optical device 10B of the second embodiment can be manufactured through the same process as the optical device 10A of the first embodiment.

[0098] Third embodiment The S-iPM laser is not limited to the configuration of the second embodiment described above. For example, the configuration of the phase modulation layer of the third embodiment can also be used to preferably realize an S-iPM laser. Fig. 14 is a plan view of a phase modulation layer 12C as a resonance mode forming layer included in an optical device according to the third embodiment. Fig. 15 is a diagram showing the positional relationship of the modified refractive index area 12b in the phase modulation layer 12C.

[0099] As shown in FIG. 14 and FIG. 15, in the unit constituent region R(x, y) of the phase modulation layer 12C, the center of gravity G of each modified refractive index region 12b is arranged on a straight line D. The straight line D passes through the corresponding lattice point O(x, y) of the unit constituent region R(x, y) and is inclined with respect to each side of the square lattice. In other words, the straight line D is inclined with respect to both the X-axis and the Y-axis. The inclination angle of the straight line D with respect to one side (X-axis) of the square lattice is θ. The inclination angle θ is constant in the phase modulation layer 12C. The inclination angle θ satisfies 0°<θ<90°, and in one example, θ=45°. Alternatively, the inclination angle θ satisfies 180°<θ<270°, and in one example, θ=225°. When the inclination angle θ satisfies 0°<θ<90° or 180°<θ<270°, the straight line D extends from the first quadrant to the third quadrant of the coordinate plane defined by the X-axis and the Y-axis. Alternatively, the inclination angle θ satisfies 90°<θ<180°, and in one example, θ=135°. Alternatively, the inclination angle θ satisfies 270°<θ<360°, and in one example, θ=315°. When the inclination angle θ satisfies 90°<θ<180° or 270°<θ<360°, the straight line D extends from the second quadrant to the fourth quadrant of the coordinate plane defined by the X-axis and the Y-axis. In this way, the inclination angle θ is an angle excluding 0°, 90°, 180°, and 270°. By setting the inclination angle θ in this way, it is possible to contribute both the light wave traveling in the X-axis direction and the light wave traveling in the Y-axis direction to the optical output beam. Here, the distance between the lattice point O(x, y) of the unit constituent region R(x, y) and the center of gravity G is defined as r(x, y). The x component indicates the position of the x-th lattice point O on the X axis, and the y component indicates the position of the y-th lattice point O on the Y axis. When the distance r(x, y) is a positive value, the center of gravity G is located in the first quadrant (or second quadrant). When the distance r(x, y) is a negative value, the center of gravity G is located in the third quadrant (or fourth quadrant). When the distance r(x, y) is 0, the lattice point O and the center of gravity G coincide with each other.

[0100] The distance r(x,y) between the center of gravity G of each modified refractive index area 12b and the corresponding lattice point O(x,y) in the unitary constituent area R(x,y) shown in FIG. 14 is set for each modified refractive index area 12b according to the desired optical image. The distribution of the distance r(x,y) has a specific value for each position (unitary constituent area) determined by the values ​​of the x component and the y component, but is not necessarily expressed by a specific function. The distribution of the distance r(x,y) is determined by extracting the phase distribution from the complex amplitude distribution obtained by performing an inverse Fourier transform on the desired optical image. That is, when the phase P(x,y) at a certain coordinate (x,y) shown in FIG. 15 is P0, the distance r(x,y) is set to 0, when the phase P(x,y) is π+P0, the distance r(x,y) is set to the maximum value R0, and when the phase P(x,y) is -π+P0, the distance r(x,y) is set to the minimum value -R0. For the intermediate phase P(x,y), the distance r(x,y) is set so that r(x,y)={P(x,y)-P0}×R0 / π. Here, the initial phase P0 can be set arbitrarily. If the lattice spacing of the square lattice is a, the maximum value R0 of r(x,y) is, for example,

number

[0101] In this third embodiment, a desired optical image can be obtained by determining the distribution of the distance r(x, y) of the modified refractive index area 12b of the phase modulation layer 12C by the following procedure. That is, under the first to fourth preconditions described in the above second embodiment, the phase modulation layer 12C is configured to satisfy the following condition. That is, the distance r(x, y) from the lattice point O(x, y) to the center of gravity G of the corresponding modified refractive index area 12b is r(x,y)=C×(P(x,y)-P0) C: Proportional constant, e.g. R0 / π P0: Any constant, e.g. 0 The corresponding modified refractive index area 12b is arranged in the unit constituent area R(x,y) so as to satisfy the relationship. That is, the distance r(x,y) is set to 0 when the phase P(x,y) at a certain coordinate (x,y) is P0, set to the maximum value R0 when the phase P(x,y) is π+P0, and set to the minimum value -R0 when the phase P(x,y) is -π+P0. When a desired optical image is to be obtained, the optical image is subjected to an inverse discrete Fourier transform, and a distribution of the distance r(x,y) according to the phase P(x,y) of the complex amplitude is given to the multiple modified refractive index areas 12b. The phase P(x,y) and the distance r(x,y) may be proportional to each other.

[0102] In the third embodiment, the refractive index structure of FIG. 14 may be applied only to a specific region of the phase modulation layer 12C. For example, as shown in FIG. 11, a refractive index structure (for example, the structure of FIG. 14) for outputting a target beam pattern may be formed inside the square inner region RIN. In this case, a circular modified refractive index region whose center of gravity coincides with the lattice point position of the square lattice is arranged in the outer region ROUT surrounding the inner region RIN. The lattice interval of the virtually set square lattice is the same both inside the inner region RIN and in the outer region ROUT. In the case of this structure, light is distributed in the outer region ROUT as well, so that it is possible to suppress the generation of high-frequency noise (so-called window function noise) caused by a sudden change in light intensity in the periphery of the inner region RIN. In addition, since light leakage in the in-plane direction can be suppressed, it is possible to increase the conversion efficiency from excitation light to light Lout.

[0103] As a method for obtaining an intensity distribution and a phase distribution from a complex amplitude distribution obtained by inverse Fourier transform, for example, the intensity distribution I(x,y) can be calculated by using the abs function of the numerical analysis software "MATLAB" by MathWorks, and the phase distribution P(x,y) can be calculated by using the angle function of MATLAB. Note that when calculating the phase distribution P(x,y) from the inverse Fourier transform result of the light image and determining the distance r(x,y) of each modified refractive index area 12b using a general discrete Fourier transform (or fast Fourier transform), the points to note are the same as those in the second embodiment described above.

[0104] In the third embodiment, the light in the second wavelength range output from the UC layer 11 is diffracted by the phase modulation layer 12C while being confined between the first light reflecting layer 13 and the second light reflecting layer 14, and as a result, forms a predetermined mode according to the lattice structure inside the phase modulation layer 12C. In the phase modulation layer 12C, the centers of gravity G of the multiple modified refractive index areas 12b are arranged on a straight line D that passes through a lattice point O of a virtual square lattice and is inclined with respect to the square lattice. Then, for each unit constituent area R(x, y), the distance r(x, y) between the center of gravity G of the modified refractive index area 12b and the corresponding lattice point O(x, y) is set individually according to the optical image. Even in such a case, compared to the case where the center of gravity G of the multiple modified refractive index areas 12b is located on the lattice point O of the square lattice (see FIG. 2), the light intensity of the light output in the thickness direction of the phase modulation layer 12C (in other words, the Z direction perpendicular to the light output surface of the optical device), i.e., the 0th order light, decreases, and the light intensity of the higher order light output in a direction inclined to that direction, for example, the +1st order light and the -1st order light, increases. Furthermore, by individually setting the distance r(x, y) between the center of gravity G of each modified refractive index area 12b and the corresponding lattice point O according to the desired light image, the phase of the light can be independently modulated for each modified refractive index area 12b, and a light image of any spatial shape can be output in the Z direction perpendicular to the light output surface and in a direction inclined to the Z direction. This light image (output light Lout) passes through the second light reflecting layer 14 and the dichroic mirror 16 and is output to the outside of the optical device.

[0105] In the optical device of the third embodiment, as in the first and second embodiments described above, light Lout having a relatively short wavelength such as green light or blue light can be output based on excitation light having a relatively long wavelength such as near-infrared light or red light. In addition, since it is not necessary to use a nitride semiconductor such as GaN for the phase modulation layer 12C and the degree of freedom in selecting the material of the phase modulation layer 12C is high, it is easy to increase the light confinement coefficient of the phase modulation layer 12C. Therefore, according to the third embodiment, it is possible to provide an optical device as a practical phase modulation light emitting element that can output a two-dimensional optical image in a relatively short wavelength range such as the visible range. The optical device of the third embodiment can be manufactured through the same process as the optical device 10A of the first embodiment.

[0106] (First Modification) FIG. 16 is a diagram showing a cross-sectional structure of a light-emitting device 1C according to a first modification. The light-emitting device 1C of the first modification includes an optical device 10C instead of the optical device 10A of the first embodiment. The configuration of the excitation light source 20A is the same as that of the first embodiment. The optical device 10C of the first modification has a diffractive optical element (DOE) 17 in addition to the configuration of the optical device 10A of the first embodiment. The diffractive optical element 17 is disposed at a position where the second light reflecting layer 14 is sandwiched between the UC layer 11 and the diffractive optical element 17. In the example of FIG. 16, the diffractive optical element 17 is formed on one of a pair of surfaces of the substrate 15, the surface opposite to the surface on which the second light reflecting layer 14 is formed. For this reason, the dichroic mirror 16 shown in FIG. 1 cannot be formed on the surface of the substrate 15. However, the dichroic mirror 16 formed on another substrate may be optically coupled to the diffractive optical element 17.

[0107] The diffractive optical element 17 is an optical device that spatially controls the phase distribution of transmitted light by unevenness (wherein the depth (height) of the unevenness is set independently for each unit constituent region R arranged two-dimensionally) formed on the surface of a light-transmitting substrate (for example, substrate 15). In this first modified example, the diffractive optical element 17 can be provided by forming unevenness on the surface of substrate 15, for example.

[0108] According to the first modification, a phase distribution based on an optical image of an arbitrary shape is formed in advance in the diffractive optical element 17, so that the laser light in the second wavelength range that passes through the second light reflecting layer 14 and is output can be converted into an optical image of an arbitrary shape. Therefore, according to the first modification, an optical image of an arbitrary shape in the second wavelength range can be output. The optical device 10C of the first modification can be suitably manufactured by performing a process of forming the diffractive optical element 17 instead of the process of forming a dielectric multilayer film as the dichroic mirror 16 on the other surface of the substrate 15 in the manufacturing process of the optical device 10A of the first embodiment. The diffractive optical element 17 is formed, for example, by applying an electron beam resist to the surface of the substrate 15, patterning the electron beam resist by electron beam drawing, and then dry etching the surface of the substrate 15. Note that a substrate other than the substrate 15 on which the diffractive optical element 17 is formed may be attached to the substrate 15.

[0109] (Second Modification) FIG. 17 is a cross-sectional view showing a manufacturing process of a light-emitting device 1D according to a second modification. The light-emitting device 1D of the second modification includes an optical device 10A1 and an excitation light source 20A. The optical device 10A1 does not include a PC layer 12A, and instead, a modified refractive index area 11b is formed in the UC layer 11, so that a part of the UC layer 11 in the thickness direction functions as a PC layer, which is different from the optical device 10A of the first embodiment. The other configurations of the optical device 10A1 are the same as those of the optical device 10A of the first embodiment. In this second modification, after the second light-reflecting layer 14 and the dichroic mirror 16 are formed on both sides of the substrate 15, an up-conversion material dispersed in a resin is applied onto the second light-reflecting layer 14. Next, the modified refractive index area 11b is formed in the resin layer by a nanoimprint method or the like to form a PC layer. Then, a first light-reflecting layer 13 is formed on the back surface 21b of the semiconductor substrate 21, and the first light-reflecting layer 13 and the PC layer are bonded together. The excitation light source is not limited to the excitation light source 20A, which is a PCSEL, and various other surface-emitting excitation light sources are applicable. The distribution of the modified refractive index region 11b is not limited to that of the first embodiment, and may be that of the second or third embodiment (see FIG. 7 or FIG. 14). In addition, in this second modified example, the first light reflecting layer 13 and the PC layer are joined to each other, but they may be separated from each other. In that case, the excitation light is spatially propagated from the first light reflecting layer 13 and supplied to the UC layer 11.

[0110] (Third Modification) 18 is a diagram showing a cross-sectional structure of a light emitting device 1E according to a third modification. The light emitting device 1E of the third modification includes an excitation light source 20B instead of the excitation light source 20A of the first modification. The configuration of an optical device 10C is similar to that of the first modification. The excitation light source 20B of the third modification is a vertical cavity surface emitting laser (VCSEL), and includes a semiconductor substrate 21, a first DBR layer 29, an active layer 22, a second DBR layer 30, a contact layer 26, a first electrode 27, and a second electrode 28.

[0111] The first DBR layer 29 and the second DBR layer 30 have a configuration for a distributed Bragg reflector (DBR), and specifically, are formed by alternately stacking a first semiconductor layer and a second semiconductor layer having a different refractive index from the first semiconductor layer. The film thickness of these first and second semiconductor layers can be determined to be λ / 4nd (nd: refractive index of the corresponding semiconductor layer) for the laser wavelength λ, and at this time, the phase of the reflected light is aligned, and a high reflectance can be obtained. The first DBR layer 29 is provided on the main surface 21a of the semiconductor substrate 21, and in one example, is in contact with the main surface 21a of the semiconductor substrate 21. The second DBR layer 30 is provided on the first DBR layer 29. The active layer 22 is provided between the first DBR layer 29 and the second DBR layer 30. The film thickness of the active layer 22 can be set to be an integer multiple of λ / 2na (na: effective refractive index of the active layer). By arranging a quantum well having optical gain at the position of an antinode of the electric field, the mode gain can be increased and the oscillation threshold current can be reduced. The contact layer 26 is provided on the second DBR layer 30. The energy band gaps of the first DBR layer 29 and the second DBR layer 30 are wider than the energy band gap of the active layer 22. The thickness directions of the semiconductor substrate 21, the active layer 22, the first DBR layer 29, the second DBR layer 30, and the contact layer 26 coincide with the Z direction.

[0112] The first electrode 27 is a metal electrode provided on the back surface 21b of the semiconductor substrate 21. The second electrode 28 is a metal electrode provided on the contact layer 26. The material and shape of the first electrode 27 and the second electrode 28 are the same as those of the excitation light source 20A of the first embodiment. Note that the contact layer 26 located outside the second electrode 28 in a plan view can be removed. In this case, current injection into unnecessary regions is suppressed, so that efficient current injection into the light emitting portion (active layer 22) becomes possible.

[0113] In one example, the semiconductor substrate 21 is a GaAs substrate. The first DBR layer 29, the active layer 22, the second DBR layer 30, and the contact layer 26 are made of GaAs-based semiconductors. The first DBR layer 29 is an AlGaAs layer. The active layer 22 has a multiple quantum well structure (barrier layer: AlGaAs / quantum well layer: InGaAs). The second DBR layer 30 is an AlGaAs layer. The contact layer 26 is a GaAs layer.

[0114] The first DBR layer 29 is given the same conductivity type as the semiconductor substrate 21, and the second DBR layer 30 and the contact layer 26 are given the opposite conductivity type to that of the semiconductor substrate 21. In one example, the semiconductor substrate 21 and the first DBR layer 29 are n-type, and the second DBR layer 30 and the contact layer 26 are p-type. The impurity concentration is, for example, 1×10 16 ~1×10 21 / cm 3 In intrinsic (i-type) crystals, where no impurities are intentionally added, the impurity concentration is 1×10 16 / cm 3 The active layer 22 is not limited to being intrinsic (i-type) and may be doped.

[0115] The excitation light source 20B of the third modified example operates as follows. When a driving current is supplied between the first electrode 27 and the second electrode 28, recombination of electrons and holes occurs in the active layer 22, and light in a first wavelength region (for example, near-infrared region) is output from the active layer 22. This light resonates in the Z direction between the first DBR layer 29 and the second DBR layer 30 to cause laser oscillation, and laser light is generated as excitation light. A part of this laser light passes through the first DBR layer 29 and is output to the optical device 10C from the rear surface 21b of the semiconductor substrate 21 through the opening 27a.

[0116] As in the third modified example, the excitation light source may be a VCSEL. In this case, the excitation light can be suitably supplied to the UC layer 11 of the optical device 10C. The light-emitting device 1E may include the optical device 10A of the first embodiment, the optical device 10B of the second embodiment, or the optical device of the third embodiment, instead of the optical device 10C. Also, as in the second modified example, the optical device and the excitation light source may be separated and optically coupled to each other.

[0117] (Fourth Modification) 19 is a diagram showing a cross-sectional structure of a light-emitting device 1F according to a fourth modified example. The light-emitting device 1F of the fourth modified example includes an optical device 10D, an excitation light source 201, and a spatial light modulator 40. The optical device 10D has a configuration in which the dichroic mirror 16 is removed from the optical device 10A of the first embodiment, but may include the dichroic mirror 16. The size of the optical device 10D as viewed from the Z direction is significantly larger than the size of the optical device 10A of the first embodiment as viewed from the Z direction.

[0118] The excitation light source 201 is integrated with the optical device 10D and supplies excitation light to the UC layer 11. The excitation light source 201 includes a plurality of excitation light sources 20A. As in the first embodiment, these excitation light sources 20A are PCSELs and are arranged at positions sandwiching the first light reflecting layer 13 between the UC layer 11 and the excitation light source 20A. In addition, these excitation light sources 20A are arranged one-dimensionally or two-dimensionally along the surface 13a of the first light reflecting layer 13. The back surface 21b of the semiconductor substrate 21 of these excitation light sources 20A faces the surface 13a of the first light reflecting layer 13 across a gap formed by the opening 27a of the first electrode 27. A slit 33 for electrical separation is formed at the boundary between the excitation light sources 20A adjacent to each other. The semiconductor substrate 21 may be common to the plurality of excitation light sources 20A. In this case, the excitation light source 201 is a laser element array in which a plurality of PCSELs are formed on a common semiconductor substrate 21.

[0119] The spatial light modulator 40 is optically coupled to the optical device 10D, and is disposed at a position sandwiching the second light reflecting layer 14 between the UC layer 11 and the spatial light modulator 40. The spatial light modulator 40 has, for example, a light transmission type configuration. In the example of Fig. 19, the spatial light modulator 40 is disposed on the opposite side of the substrate 15 from the second light reflecting layer 14. The spatial light modulator 40 may be integrated with the optical device 10D, or may be disposed apart from the optical device 10D.

[0120] The spatial light modulator 40 has a plurality of pixels arranged two-dimensionally, and modulates the phase of the laser light Lout1 output from the optical device 10D independently for each pixel by presenting a hologram to the plurality of pixels. The spatial light modulator 40 has, for example, a liquid crystal type configuration. When the spatial light modulator 40 is a liquid crystal type, individual voltages constituting a hologram are applied to a plurality of pixel electrodes arranged two-dimensionally. This controls the magnitude of the electric field applied to the liquid crystal layer for each pixel electrode. The optical path length in the liquid crystal layer of each pixel changes according to the magnitude of the electric field. Therefore, the phase of light can be modulated independently for each pixel. Note that the type of the spatial light modulator 40 is not limited to the liquid crystal type, and various types of spatial light modulators may be applied. The spatial light modulator 40 outputs the light image Lout2 after being phase-modulated by the hologram.

[0121] According to the fourth modification, by presenting a phase pattern based on an optical image of an arbitrary shape in the spatial light modulator 40, the laser light Lout1 in the second wavelength range outputted after passing through the second light reflecting layer 14 can be converted into an optical image Lout2 of an arbitrary shape. Therefore, according to the fourth modification, an optical image Lout2 of an arbitrary shape in the second wavelength range can be outputted. In addition, by changing the phase pattern presented to the spatial light modulator 40 over time, it is also possible to dynamically change the optical image Lout2.

[0122] Also, as in the fourth modification, the excitation light source 201 includes a plurality of excitation light sources 20A, and the plurality of excitation light sources 20A may be arranged one-dimensionally or two-dimensionally along the surface 13a of the first light reflecting layer 13. The optical transmittance of the first light reflecting layer 13 in the wavelength region (first wavelength region) of the excitation light may be greater than the optical transmittance of the first light reflecting layer 13 in the emission wavelength region (second wavelength region) of the UC layer 11. In this case, the excitation light output from the excitation light source 201 passes through the first light reflecting layer 13 and is supplied to the UC layer 11, so that the laser light Lout1 in the second wavelength region can be suitably output from the optical device 10D. Also, according to the light-emitting device 1F of the fourth modification, the excitation light is generated using a plurality of excitation light sources 20A arranged in a one-dimensional or two-dimensional manner, so that the area of ​​the optical device 10D as viewed from the light output direction can be made larger. Therefore, the area of ​​the light image Lout2 output from the light-emitting device 1F can be made larger.

[0123] In manufacturing the light emitting device 1F according to the fourth modification, after the step of forming the first electrode 27 and the second electrode 28 of the first embodiment, element separation is performed by forming the slit 33. In addition, instead of the step of forming a dielectric multilayer film as the dichroic mirror 16 on the other surface of the substrate 15, a step of arranging a spatial light modulator 40 is performed. In addition, the first light reflecting layer 13, the PC layer 12A, and the UC layer 11 are formed on one surface of a light-transmitting substrate (for example, a quartz substrate), and the back surface of the substrate is joined to the first electrode 27.

[0124] (Fifth Modification) FIG. 20 is a cross-sectional view showing a manufacturing process of a light-emitting device 1G according to the fifth modification. This light-emitting device 1G includes an optical device 10E and an excitation light source 201. The optical device 10E does not include a PC layer 12A, and instead, a modified refractive index area 11b is formed in the UC layer 11, so that a part of the UC layer 11 in the thickness direction functions as a PC layer. The other configurations of the optical device 10E are the same as those of the optical device 10D of the fourth modification. In the fifth modification, after a second light-reflecting layer 14 is formed on one surface of the substrate 15, an upconversion material dispersed in a resin is applied onto the second light-reflecting layer 14. Then, a PC layer is formed by forming a modified refractive index area 11b in the resin layer by a nanoimprint method or the like. Then, a first light-reflecting layer 13 is formed on one surface of a light-transmitting substrate 18, and the first light-reflecting layer 13 and the PC layer are bonded to each other. In addition, the other surface of the substrate 18 is bonded to a first electrode 27. Finally, the spatial light modulator 40 is disposed. The distribution of the modified refractive index area 11b is not limited to that of the first embodiment, and may be that of the second or third embodiment (see FIG. 7 or FIG. 14). In the fifth modified example, the first light reflecting layer 13 and the PC layer are joined to each other, but they may be separated from each other. In that case, the excitation light is spatially propagated from the first light reflecting layer 13 and supplied to the UC layer 11.

[0125] (Sixth Modification) FIG. 21 is a diagram showing a cross-sectional structure of a light-emitting device 1G according to a sixth modified example. In addition to the configuration of the light-emitting device 1F according to the fourth modified example, the light-emitting device 1G according to the sixth modified example further includes a lens 41 arranged on the side of the optical device 10D (in a direction intersecting the Z direction). The UC layer 11 is supplied with excitation light Lex1 from the side of the optical device 10D through the lens 41. The excitation light Lex1 is light output from an excitation light source (e.g., a laser diode or a PCSEL) other than the excitation light source 201. The wavelength of the excitation light Lex1 is equal to the wavelength of the excitation light output from the excitation light source 201. As in the sixth modified example, the UC layer 11 may further be supplied with excitation light Lex1 other than the excitation light supplied from the excitation light source 201. In this case, the density of the excitation light supplied to the UC layer 11 increases, and the emission intensity of the light output from the UC layer 11 further increases, so that the oscillation threshold of the optical device 10D can be easily exceeded.

[0126] (Seventh Modification) 22 is a diagram showing a cross-sectional structure of a light-emitting device 1H according to a seventh modification. The light-emitting device 1H of the seventh modification includes an excitation light source 202 instead of the excitation light source 201 of the third modification. The excitation light source 202 is integrated with the optical device 10D and supplies excitation light to the UC layer 11. The excitation light source 202 includes a plurality of excitation light sources 20C. These excitation light sources 20C are PCSELs and are disposed on the opposite side of the UC layer 11 with respect to the first light reflecting layer 13. Moreover, these excitation light sources 20C are arranged one-dimensionally or two-dimensionally along the surface 13a of the first light reflecting layer 13.

[0127] The excitation light source 20C includes a first electrode 31 instead of the first electrode 27 included in the excitation light source 20A of the first embodiment. The other configurations of the excitation light source 20C are the same as those of the excitation light source 20A. The first electrode 31 is made of a transparent conductive film having optical transparency at least to the wavelength of the excitation light, and is provided over the entire surface of the rear surface 21b of the semiconductor substrate 21. The first light reflecting layer 13 of the optical device 10D faces the first electrode 31, and in one example, is in contact with the first electrode 31. Various materials can be used for the transparent conductive film, such as indium tin oxide (ITO), a zinc oxide-based transparent conductive film, and a tin oxide-based transparent conductive film.

[0128] In the seventh modification, a driving current is supplied between the first electrode 31 and the second electrode 28. Then, the excitation light generated in each excitation light source 20C passes through the first electrode 31 to reach the first light reflecting layer 13, and is further passed through the first light reflecting layer 13 to be supplied to the UC layer 11. Note that the semiconductor substrate 21 may be common to the multiple excitation light sources 20C. In this case, the excitation light source 202 is a laser element array in which multiple PCSELs are formed on the common semiconductor substrate 21.

[0129] (Eighth Modification) FIG. 23 is a diagram showing a cross-sectional structure of a light-emitting device 1J according to an eighth modification. The light-emitting device 1J of the eighth modification includes an optical device 10A having a configuration similar to that of the first embodiment, and an excitation light source 42. The excitation light source 42 is disposed away from the optical device 10A, and supplies excitation light Lex2 in a first wavelength range to the UC layer 11 of the optical device 10A. Therefore, the excitation light source 42 is spatially optically coupled to the UC layer 11 of the optical device 10A. In addition, the excitation light source 42 is optically coupled to the side surface of the UC layer 11, so that the excitation light Lex2 is supplied to the UC layer 11 without passing through the first light reflecting layer 13 and the second light reflecting layer 14. Therefore, in both the first light reflecting layer 13 and the second light reflecting layer 14, light transmission characteristics for the excitation light Lex2 are not required, so that, for example, other light reflecting films such as a metal film can be applied as the first light reflecting layer 13 instead of the dielectric multilayer film.

[0130] (Ninth Modification) A modification of the phase modulation layer 12B of the second embodiment will be described in detail. In this ninth modification, the lattice interval a of the virtual square lattice and the emission wavelength λ of the UC layer 11 satisfy the condition of M-point oscillation. Furthermore, when considering the reciprocal lattice space (wave number space) in the phase modulation layer 12B, four in-plane wave number vectors are formed that are phase modulated by the rotation angle distribution φ(x, y) and show standing waves each including a wave number spread corresponding to the angle spread of the light that forms the optical image. And, the magnitude of at least one of the in-plane wave number vectors is smaller than 2π / λ (light line). These points will be described in detail below.

[0131] First, for comparison, a photonic crystal laser (PCSEL) that oscillates at the Γ point in reciprocal lattice space will be described. A PCSEL has an active layer and a PC layer in which a number of modified refractive index regions are periodically arranged in a two-dimensional manner. The PCSEL outputs laser light along the normal direction to the principal surface of the semiconductor substrate while forming a standing wave with an oscillation wavelength corresponding to the arrangement period of the modified refractive index regions in a plane perpendicular to the thickness direction of the PC layer. In addition, for Γ point oscillation, it is preferable that the lattice spacing a of the virtual square lattice, the emission wavelength λ of the UC layer 11, and the equivalent refractive index (effective refractive index) n of the mode satisfy the condition: λ=na.

[0132] FIG. 24 is a plan view showing a reciprocal lattice space (wave number space) for a PC layer of a PCSEL that oscillates at the Γ point. This FIG. 24 shows a case where a plurality of modified refractive index areas are located on lattice points of a square lattice, and point P in FIG. 24 shows a reciprocal lattice point. Also, arrow B1 in FIG. 24 shows a primitive reciprocal lattice vector, and each of arrows B2 shows a reciprocal lattice vector that is twice the primitive reciprocal lattice vector B1. Also, arrows K1, K2, K3, and K4 show four in-plane wave number vectors. The four in-plane wave number vectors K1, K2, K3, and K4 combine with each other through diffractions of 90° and 180° to form a standing wave state. Here, Γ-X axis and Γ-Y axis that are orthogonal to each other in the reciprocal lattice space are defined. The Γ-X axis is parallel to one side of the square lattice, and the Γ-Y ​​axis is parallel to the other side of the square lattice. An in-plane wave vector is a vector obtained by projecting a wave vector onto the Γ-X Γ-Y plane. That is, the in-plane wave vector K1 faces the positive direction of the Γ-X axis, the in-plane wave vector K2 faces the positive direction of the Γ-Y ​​axis, the in-plane wave vector K3 faces the negative direction of the Γ-X axis, and the in-plane wave vector K4 faces the negative direction of the Γ-Y ​​axis. As is clear from FIG. 24, in a PCSEL that oscillates at the Γ point, the magnitude of the in-plane wave vectors K1 to K4 (i.e., the magnitude of the standing wave in the in-plane direction) is equal to the magnitude of the fundamental reciprocal lattice vector B1. The magnitude k of the in-plane wave vectors K1 to K4 is given by the following formula (9):

number

[0133] Fig. 25 is a three-dimensional perspective view of the reciprocal lattice space shown in Fig. 24. Fig. 25 shows a Z-axis perpendicular to the Γ-X and Γ-Y axes. This Z-axis is the same as the Z-axis shown in Fig. 1. As shown in Fig. 25, in a PCSEL oscillating at the Γ point, the wave number in the in-plane direction becomes 0 due to diffraction, and diffraction occurs in the direction perpendicular to the plane (Z-axis direction) (arrow K5 in the figure). Therefore, the laser light is basically output in the Z-axis direction.

[0134] Next, a PCSEL that lases at point M will be described. For lasing at point M, the lattice spacing a of a virtual square lattice, the emission wavelength λ of the UC layer 11, and the equivalent refractive index n of the mode must satisfy the following condition: λ=(2 1 / 2 )n×a. FIG. 26 is a plan view showing a reciprocal lattice space (wave number space) for a PC layer of a PCSEL that oscillates at point M. FIG. 26 also shows a case where a plurality of modified refractive index areas are located on lattice points of a square lattice, and point P in FIG. 26 represents a reciprocal lattice point. Arrow B1 in FIG. 26 indicates a fundamental reciprocal lattice vector similar to that in FIG. 24, and arrows K6, K7, K8, and K9 indicate four in-plane wave number vectors. Here, the Γ-M1 axis and the Γ-M2 axis that are orthogonal to each other in the reciprocal lattice space are defined. The Γ-M1 axis is parallel to one diagonal direction of the square lattice, and the Γ-M2 axis is parallel to the other diagonal direction of the square lattice. The in-plane wave number vector is a vector obtained by projecting a wave number vector into the Γ-M1·Γ-M2 plane. That is, the in-plane wave number vector K6 faces the positive direction of the Γ-M1 axis. The in-plane wave vector K7 points in the positive direction of the Γ-M2 axis. The in-plane wave vector K8 points in the negative direction of the Γ-M1 axis. The in-plane wave vector K9 points in the negative direction of the Γ-M2 axis. As is clear from FIG. 26, in a PCSEL oscillating at point M, the magnitude of the in-plane wave vectors K6 to K9 (i.e., the magnitude of the standing wave in the in-plane direction) is smaller than the magnitude of the fundamental reciprocal lattice vector B1. The magnitude k of the in-plane wave vectors K6 to K9 is given by the following equation (10):

number

[0135] Next, an S-iPM laser that oscillates at the Γ point will be described. The conditions for Γ point oscillation are the same as those for the PCSEL described above. FIG. 27 is a plan view showing a reciprocal lattice space relating to the phase modulation layer of an S-iPM laser that oscillates at the Γ point. The fundamental reciprocal lattice vector B1 is the same as that of the PCSEL that oscillates at the Γ point (see FIG. 24), but the in-plane wave vectors K1 to K4 are phase modulated by the rotation angle distribution φ(x, y), and each has a wave number spread SP corresponding to the spread angle of the optical image. The wave number spread SP is centered on the tip of each in-plane wave vector K1 to K4 in the PCSEL that oscillates at the Γ point, and the lengths of the sides in the x-axis direction and y-axis direction are 2Δkx max , 2Δky max Due to such wave number spread SP, each in-plane wave number vector K1 to K4 spreads in a rectangular range of (Kix + Δkx, Kiy + Δky) (i = 1 to 4, Kix is ​​the x-component of vector Ki, and Kiy is the y-component of vector Ki). Here, -Δkx max ≦Δkx≦Δkx max , -Δky max ≦Δky≦Δky max In addition, Δkx max and Δky max The magnitude of is determined according to the spread angle of the light image. In other words, Δkx max and Δky max The size of depends on the light image to be displayed.

[0136] Fig. 28 is a three-dimensional perspective view of the reciprocal lattice space shown in Fig. 27. Fig. 28 shows a Z axis perpendicular to the direction along the Γ-X axis and the direction along the Γ-Y ​​axis. This Z axis is the same as the Z axis shown in Fig. 1. As shown in Fig. 28, in the case of an S-iPM laser oscillating at the Γ point, an optical image (beam pattern) LM having a two-dimensional spread is output, which includes not only the 0th order light in the direction perpendicular to the surface (Z-axis direction), but also +1st order light and -1st order light in a direction inclined with respect to the Z-axis direction.

[0137] Next, the S-iPM laser that oscillates at the M point will be described. The conditions for the M point oscillation are the same as those for the PCSEL described above. FIG. 29 is a plan view showing the reciprocal lattice space related to the phase modulation layer of the S-iPM laser that oscillates at the M point. The fundamental reciprocal lattice vector B1 is the same as that of the PCSEL with M point oscillation (see FIG. 26), but the in-plane wave vectors K6 to K9 each have a wave number spread SP due to the rotation angle distribution φ(x, y). The shape and size of the wave number spread SP are the same as those for the Γ point oscillation described above. In the S-iPM laser, the magnitude of the in-plane wave vectors K6 to K9 (i.e., the magnitude of the standing wave in the in-plane direction) is smaller than the magnitude of the fundamental reciprocal lattice vector B1 in the case of M point oscillation (the wave number in the in-plane direction cannot become 0 due to diffraction, and no diffraction occurs in the direction perpendicular to the plane (Z-axis direction)). Therefore, neither the 0th order light in the direction perpendicular to the plane (Z-axis direction) nor the +1st order light and the -1st order light in the direction inclined with respect to the Z-axis direction are output.

[0138] Here, in this ninth modified example, the following device is applied to the phase modulation layer 12B in the S-iPM laser oscillating at point M, so that the zeroth order light is not output, but a part of the +1st order light and the -1st order light is output. Specifically, as shown in FIG. 30, a diffraction vector V having a certain magnitude and direction is added to the in-plane wave vectors K6 to K9, so that the magnitude of at least one of the in-plane wave vectors K6 to K9 (in the figure, the in-plane wave vector K8) is set to be smaller than 2π / λ. In other words, at least one of the in-plane wave vectors K6 to K9 (in-plane wave vector K8) after the diffraction vector V is added falls within a circular region (light line) LL of radius 2π / λ. In FIG. 30, the in-plane wave vectors K6 to K9 shown by the dashed line indicate the state before the diffraction vector V is added, and the in-plane wave vectors K6 to K9 shown by the solid line indicate the state after the diffraction vector V is added. The light line LL corresponds to the total reflection condition, and the wave vector whose magnitude falls within the light line LL has a component in the direction perpendicular to the surface (Z-axis direction). In one example, the direction of the diffraction vector V is along the Γ-M1 axis or the Γ-M2 axis, and its magnitude is 2π / (2 1 / 2 )a-π / λ to 2π / (2 1 / 2)a+π / λ (for example, 2π / (2 1 / 2 )a).

[0139] The magnitude and direction of the diffraction vector V for placing at least one of the in-plane wave vectors K6 to K9 within the light line LL will be considered. The following equations (11) to (14) respectively represent the in-plane wave vectors K6 to K9 before the diffraction vector V is added.

number

number

number

number

number

number

number

number

number

number

number

number

[0140] The size (radius) of the light line LL is set to 2π / λ for the following reason. FIG. 31 is a diagram for explaining the peripheral structure of the light line LL, and shows the boundary between the device and air as viewed from a direction perpendicular to the Z-axis direction. The magnitude of the wave vector of light in a vacuum is 2π / λ, but when light propagates through the device medium as shown in FIG. 31, the magnitude of the wave vector Ka in the medium with a refractive index of n is 2πn / λ. At this time, in order for light to propagate through the boundary between the device and air, the wave number component parallel to the boundary must be continuous (law of conservation of wave number). When the wave vector Ka and the Z axis form an angle θ in FIG. 31, the length of the wave vector Kb projected in the plane (i.e., the in-plane wave vector) is (2πn / λ) sinθ. On the other hand, generally, due to the relationship of the refractive index of the medium n>1, the law of conservation of wave number does not hold at an angle where the in-plane wave vector Kb in the medium is larger than 2π / λ. At this time, the light is totally reflected and cannot be extracted to the air side. The magnitude of the wave vector corresponding to this total reflection condition is the magnitude of the light line LL, which is 2π / λ.

[0141] As an example of a specific method for adding the diffraction vector V to the in-plane wave vectors K6 to K9, a method of superimposing a rotation angle distribution φ2(x,y) (second phase distribution) that is unrelated to the optical image on a rotation angle distribution φ1(x,y) (first phase distribution) that is a phase distribution for forming a desired optical image can be considered. In this case, the rotation angle distribution φ(x,y) of the phase modulation layer 12B is φ(x,y)=φ1(x,y)+φ2(x,y) where φ1(x,y) corresponds to the phase of the complex amplitude when the optical image is inverse Fourier transformed as described above. Also, φ2(x,y) is the rotation angle distribution for adding the diffraction vector V that satisfies the above formula (22). FIG. 32 is a conceptual diagram showing an example of the rotation angle distribution φ2(x,y). As shown in FIG. 32, in this example, the first phase value φ A and the first phase value φ A A second phase value φ different from B That is, the first phase value φ A A second phase value φ different from B In one example, the first phase value φ A is 0 (rad), and the second phase value φ B is π (rad). That is, the first phase value φ A and the second phase value φ B The first phase value φ changes by π. By arranging the phase values ​​in this way, a diffraction vector V along the Γ-M1 axis or the Γ-M2 axis can be suitably realized. A and the second phase value φ B When the first and second phase values ​​φ are arranged in a checkerboard pattern as described above, the diffraction vector V is offset by the wave vectors K6 to K9 in FIG. 29, such that V=(±π / a, ±π / a). A ,φ B By changing the arrangement direction from 45°, the direction of the diffraction vector V can be adjusted to any direction.

[0142] In the structure of the ninth modification, the material system, film thickness, and layer configuration can be changed in various ways as long as the structure includes the UC layer 11 and the phase modulation layer 12B. Here, the scaling law holds for a so-called square lattice photonic crystal laser in which the perturbation from the virtual square lattice is zero. That is, when the wavelength is multiplied by a constant α, a similar standing wave state can be obtained by multiplying the entire square lattice structure by α. Similarly, in this modification, the structure of the phase modulation layer 12B can be determined by the scaling law according to the wavelength.

[0143] The effect obtained by the phase modulation layer 12B according to the ninth modification described above will be described. In this ninth modification, the lattice interval a of the virtual square lattice and the emission wavelength λ of the UC layer 11 satisfy the condition of M-point oscillation. Usually, in the standing wave state of M-point oscillation, the light propagating in the phase modulation layer 12B is totally reflected, and the output of both the signal light (+1st order light and -1st order light) and the 0th order light is suppressed. However, in the ninth modification, the magnitude of at least one of the in-plane wave vectors K6 to K9 in four directions, which are in-plane wave vectors formed in the reciprocal lattice space of the phase modulation layer 12B and each include the wave number spread Δk due to the rotation angle distribution φ(x, y), is smaller than 2π / λ (light line LL). In the S-iPM laser, for example, by devising the rotation angle distribution φ(x, y), it is possible to adjust such in-plane wave vectors K6 to K9. If the magnitude of at least one in-plane wave vector is smaller than 2π / λ, the in-plane wave vector has a component in the Z-axis direction, and as a result, a part of the signal light is output from the phase modulation layer 12B. However, the zeroth-order light is still confined within the plane in a direction that coincides with one of the four wave vectors (±π / a, ±π / a) that form the standing wave at point M, and is not output from the phase modulation layer 12B into the light line. In other words, according to this ninth modification, the zeroth-order light contained in the output of the S-iPM laser can be removed from the light line, and only the signal light can be output into the light line.

[0144] Also, as in the ninth modification, the rotation angle distribution φ(x,y) may be a superposition of the rotation angle distribution φ1(x,y) according to the optical image and the rotation angle distribution φ2(x,y) unrelated to the optical image. In this case, the rotation angle distribution φ2(x,y) may be a rotation angle distribution for adding a diffraction vector V having a certain magnitude and direction to the in-plane wave vectors K6 to K9 in four directions due to the rotation angle distribution φ1(x,y) in the reciprocal lattice space of the phase modulation layer 12B. As a result of adding the diffraction vector V to the in-plane wave vectors K6 to K9 in four directions, the magnitude of at least one of the in-plane wave vectors K6 to K9 in the four directions may be smaller than 2π / λ. This makes it possible to easily realize a configuration in which the magnitude of at least one of the in-plane wave vectors K6 to K9 in the four directions, including the wave number spreads Δkx and Δky due to the rotation angle distribution φ(x,y) in the reciprocal lattice space, is smaller than 2π / λ (light line).

[0145] As in the ninth modification, the rotation angle distribution φ2(x,y) has different phase values ​​φ A ,φ B Alternatively, the rotation angle distribution φ2(x,y) may be arranged in a checkerboard pattern. The above-mentioned diffraction vector V can be easily realized by using such a rotation angle distribution φ2(x,y).

[0146] FIG. 33 is a diagram showing an example of the rotation angle distribution φ(x,y) of the phase modulation layer 12B. FIG. 34 is a diagram showing an enlarged view of a portion S shown in FIG. 33. In FIG. 33 and FIG. 34, the magnitude of the rotation angle is represented by a shade of color, and the darker the region, the larger the rotation angle (i.e., the larger the phase angle). Referring to FIG. 34, it can be seen that a pattern in which different phase values ​​are arranged in a checkerboard pattern is superimposed. FIG. 35 shows a beam pattern (light image) output from an optical element having the rotation angle distribution φ(x,y) shown in FIG. 33. FIG. 36 is a schematic diagram of the beam pattern shown in FIG. 21. The centers of FIG. 35 and FIG. 36 correspond to the Z axis. As is clear from Figures 35 and 36, the optical element outputs +1st order light including a first light image portion LM1 that is output in a first direction inclined with respect to the Z axis, and -1st order light that is output in a second direction that is symmetrical to the first direction with respect to the Z axis and includes a second light image portion LM2 that is rotationally symmetrical to the first light image portion LM1 with respect to the Z axis, but does not output 0th order light traveling on the Z axis.

[0147] In this ninth modified example, a pattern including the Z axis and symmetrical with respect to the Z axis can also be output. In this case, since there is no zero-order light, the intensity unevenness of the pattern does not occur even on the Z axis. Design examples of such beam patterns include 5×5 multipoint, mesh, and one-dimensional patterns. Schematic diagrams of these beam patterns are shown in Figures 37(a), 38(a), and 39(a), and phase distributions of the beam patterns are shown in Figures 37(b), 38(b), and 39(b). By outputting such beam patterns in the visible range, applications such as display applications become possible.

[0148] (Tenth Modification) In the tenth modification, in the phase modulation layer 12C of the third embodiment, the lattice spacing a of the virtual square lattice and the emission wavelength λ of the UC layer 11 satisfy the condition for M-point oscillation, as in the above-mentioned ninth modification. Furthermore, when considering the reciprocal lattice space in the phase modulation layer 12C, the magnitude of at least one of the in-plane wave vectors in four directions, each of which includes the wave number spread due to the distribution of the distance r(x, y), is smaller than 2π / λ (light line).

[0149] More specifically, in the tenth modification, the following device is applied to the phase modulation layer 12C in the S-iPM laser oscillating at point M, so that the 0th order light is not outputted into the light line, and a part of the +1st order light and the -1st order light is outputted. Specifically, as shown in FIG. 30, a diffraction vector V having a certain magnitude and direction is added to the in-plane wave vectors K6 to K9, so that the magnitude of at least one of the in-plane wave vectors K6 to K9 is set to be smaller than 2π / λ. In other words, at least one of the in-plane wave vectors K6 to K9 after the diffraction vector V is added falls within a circular region (light line) LL with a radius of 2π / λ. That is, by adding a diffraction vector V that satisfies the above-mentioned formula (22), one of the in-plane wave vectors K6 to K9 falls within the light line LL, and a part of the +1st order light and the -1st order light is outputted.

[0150] In the tenth modification, the lattice spacing a of the virtual square lattice and the emission wavelength λ of the UC layer 11 satisfy the condition of M-point oscillation, and the plane wave forming the standing wave is phase-modulated by the distribution of the distance r(x, y) in the reciprocal lattice space of the phase modulation layer 12C, and the magnitude of at least one of the four-directional in-plane wave vectors K6 to K9, each including the wave number spread Δk due to the angular spread of the optical image, is smaller than 2π / λ (light line). Alternatively, by adding the diffraction vector V to the four-directional in-plane wave vectors K6 to K9 excluding the wave number spread Δk, the magnitude of at least one in-plane wave vector is smaller than the value {(2π / λ)-Δk} obtained by subtracting the wave number spread Δk from 2π / λ. Therefore, the zero-order light included in the output of the S-iPM laser can be removed from the light line, and only the signal light can be output.

[0151] The optical device and the light emitting device according to the present disclosure are not limited to the above-mentioned embodiment, and various other modifications are possible. For example, although the pump light sources 20A and 20C are PCSELs in the above description, the pump light sources 20A and 20C may be S-iPMSELs.

[0152] (Fourth embodiment) In the above-mentioned first to third embodiments and first to tenth modifications, light-emitting devices 1A to 1H, 1J are disclosed in which electrodes are arranged on the back side of the excitation light sources 20A to 20C and optical devices 10A to 10E, 10A1 having a UC layer (up-conversion layer) are provided. However, in manufacturing these light-emitting devices, when electrodes are formed on the back side of the excitation light sources 20A to 20C that serve as light source parts, a highly accurate electrode formation technique is required. That is, in an optical device in which electrodes are provided on the back side of the excitation light sources, high flatness and parallelism are required for the surfaces of the two light confinement layers and the UC layer and PC layer (or phase modulation layer) sandwiched therebetween so as not to disturb the in-plane guided mode. In particular, in the above-mentioned embodiments and modifications, since the light confinement layers are formed with an opening provided in the electrode on the back side of the excitation light source, it is important to ensure the above-mentioned flatness and parallelism. In this fourth embodiment, in order to ease such severe manufacturing conditions, the electrode arrangement of the excitation light source is changed to have a device structure in which an optical device is provided on the flat back side of the excitation light source.

[0153] On the other hand, the optical devices 10A to 10E and 10A1 serving as the resonator portion are applied with a first light reflecting layer and a second light reflecting layer, both of which are made of a dielectric multilayer film, as light confinement layers. However, in the fourth embodiment, instead of at least the second light reflecting layer of the first light reflecting layer and the second light reflecting layer, a light confinement layer made of a single material having a substantially uniform refractive index distribution along the stacking direction of the optical device and a refractive index lower than that of the UC layer is applied. In this case, the manufacturing process can be simplified compared to the dielectric multilayer film, and in particular, the layer thickness of the single-layered light confinement layer replacing the second light reflecting layer can be reduced. The thinning of the light confinement layer is expected to suppress the formation of higher-order modes along the stacking direction of the optical device. In addition, when a single-layered light confinement layer is adopted instead of the second light reflecting layer, it is also possible to embed a PC layer (photonic crystal layer) adjacent to the UC layer inside or on the surface of the light confinement layer (a resonator structure that is easy to oscillate).

[0154] Furthermore, in the optical device according to the fourth embodiment, the PC layer (or the phase modulation layer) is disposed closer to the output side than the UC layer. With this configuration, even if the UC layer contains a scattering material, the effect on the formation of the resonance mode is small, the increase in the oscillation threshold is prevented, and the noise mixed into the output wavefront (beam pattern) can be reduced.

[0155] FIG. 40 is a schematic diagram for explaining the configuration of the light-emitting device according to the fourth embodiment, in comparison with the light-emitting device according to the first embodiment as an example. The optical device 100A indicated by the arrow (a) and the optical device 100B indicated by the arrow (b) can be replaced with the optical devices 10A to 10E and 10A1 described above. The pumping light source 200A indicated by the arrow (c) can also be replaced with the pumping light sources 20A to 20C described above. As in the above-mentioned embodiments and modifications, a structure in which a plurality of pumping light sources 200A (each of the pumping light sources 200A includes a photonic crystal surface-emitting laser) is applied to one optical device 100A to 100F can also be applied. Furthermore, as in the above-mentioned embodiments and modifications, the light-emitting device according to the fourth embodiment can also have any of the dichroic mirror 16, the diffractive optical element 17, and the spatial light modulator 40 disposed on the opposite side of the UC layer 11 with respect to the second light confinement layer 140. In addition, in all the drawings showing the structure of the light-emitting device according to the fourth embodiment, the dichroic mirror 16, the diffractive optical element 17, and the spatial light modulator 40 are omitted.

[0156] In the example of FIG. 40, the optical device 100A indicated by the arrow (a) has a substrate 15 (a quartz plate having optical transparency), a second optical confinement layer 430 provided on one surface of the substrate 15, a PC layer 120 (which may be a phase modulation layer) provided on the second optical confinement layer 140, a UC layer 11 provided on the PC layer 120, and a first optical confinement layer 130 provided on the UC layer 11. On the other surface of the substrate 15, any one of a dichroic mirror 16, a diffractive optical element 17, and a spatial light modulator 40 may be disposed, as in the first to third embodiments and the first to tenth modified examples described above. The PC layer 120 is constituted by a basic layer 120a and a plurality of PC layers 120 having a refractive index different from that of the basic layer 120a, and the second optical confinement layer 140 has a single-layer structure having a substantially uniform refractive index distribution along the thickness direction. In the optical device 100A, the first optical confinement layer 130 may have a dielectric multilayer film or a single layer structure.

[0157] In the example of FIG. 40, the optical device 100B indicated by the arrow (b) has a substrate 15 having optical transparency, a second optical confinement layer 140 provided on one surface of the substrate 15, a PC layer 120 (which may be a phase modulation layer) provided inside or on the surface of the second optical confinement layer 140, a UC layer 11 provided on the second optical confinement layer 140 including the PC layer 120, and a first optical confinement layer 130 provided on the UC layer 11. On the other surface of the substrate 15, any one of a dichroic mirror 16, a diffractive optical element 17, and a spatial light modulator 40 may be disposed, as in the optical device 100A. The PC layer 120 embedded in the second optical confinement layer 140 is constituted by a basic layer 120a and a plurality of PC layers 120 having a refractive index different from that of the basic layer 120a, and the second optical confinement layer 140 is made of a single material having a substantially uniform refractive index distribution along the thickness direction (has a single-layer structure). In this optical device 100B as well, the first optical confinement layer 130 may be a dielectric multilayer film or a single layer structure.

[0158] In the example of Figure 40, the excitation light source 200A (including a semiconductor laminate functioning as a photonic crystal surface-emitting laser) indicated by arrow (c) comprises a semiconductor substrate 21, a first cladding layer 24 (layer functioning as an optical confinement layer) provided on the primary surface 21a of the semiconductor substrate 21, an active layer 22 provided on the first cladding layer 24, a PC layer 23 provided on the active layer 22, a second cladding layer 25 (layer functioning as an optical confinement layer) provided on the PC layer 23, a contact layer 26 provided on the second cladding layer 25, a second electrode 28 (p-electrode) provided on the semiconductor laminate including the active layer 22 and the PC layer 23, and a first electrode 27 (n-electrode) provided on the primary surface 21a of the semiconductor substrate 21. In addition, the pumping light source 200A shown in Fig. 40 discloses a first optical confinement layer 130 constituting a part of the optical device 100A or the optical device 100B on the back surface 21b of the semiconductor substrate 21. This is because there is a manufacturing form in which the first optical confinement layer 130 is provided on the back surface 21b of the semiconductor substrate 21 in the final stage of the manufacturing process of the pumping light source 200A described later. In addition, in the pumping light source 200A shown in Fig. 40, the first optical confinement layer 130 provided on the back surface 21b of the semiconductor substrate 21 is shown as a dielectric multilayer film, but similar to the above-mentioned second optical confinement layer 140, a single layer structure having a substantially uniform refractive index distribution along the thickness direction may be adopted.

[0159] In particular, in the excitation light source 200A in the fourth embodiment, both the first electrode 27 and the second electrode 28 are disposed on the principal surface 21a side of the semiconductor substrate 21. Therefore, the area of ​​the PC layer 23 viewed from the stacking direction of the semiconductor laminate (photonic crystal surface emitting laser) is smaller than the area of ​​the UC layer 11 viewed from the stacking direction of the above-mentioned optical devices 100A and 100B, more specifically, the area of ​​the principal surface 21a of the semiconductor substrate 21 (the first electrode 27 is provided on an area of ​​the principal surface 21a of the semiconductor substrate 21 that is exposed and not covered by the semiconductor laminate). With such an electrode arrangement, both the first electrode and the second electrode are disposed on the principal surface 21a side of the semiconductor substrate 21, which facilitates the mounting operation of the light-emitting device of the present disclosure on the submount and enables the effective area to be expanded.

[0160] The light emitting device according to the fourth embodiment having the above-mentioned structure can be manufactured by a unit assembly type (first manufacturing method) or an upconversion material injection type (second manufacturing method). First, the manufacturing method of the unit assembly type will be described in detail with reference to Figs. 41 to 44. The following description will be given. Fig. 41 is a diagram for explaining the manufacturing process of the excitation light source 200A as the light emitting section in the manufacturing process (first manufacturing method) of the unit assembly type of the light emitting device according to the fourth embodiment. Figs. 42(a) and 42(b) are diagrams for explaining the mounting process of the excitation light source on the submount in the first manufacturing method. Figs. 43(a) and 43(b) are diagrams for explaining the manufacturing process of the optical device (resonator section) in the first manufacturing method, and Fig. 43(c) is a diagram for explaining the mounting process of the optical device on the submount on which the excitation light source has already been mounted in the first manufacturing method. Figs. 44(a) and 44(b) show a plan view and a cross-sectional view of the light emitting device after manufacturing.

[0161] The manufacturing process of the excitation light source 200A is performed in the order of the arrows (a), (b), and (c) as shown in FIG. 41. First, the first cladding layer 24, the active layer 22, the PC layer 23 composed of the base layer 23a and a plurality of modified refractive index areas 23b, the second cladding layer 25, and the contact layer 26 are provided in this order on the main surface 21a of the semiconductor substrate 21 having a width of 800 μm or more. The diffraction grating area of ​​the PC layer 23 may be about 400 μm in width. The semiconductor laminate thus provided on the main surface 21a of the semiconductor substrate 21 is manufactured in the same manner as the excitation light sources 20A to 20C of the first to third embodiments and the first to tenth modified examples described above.

[0162] Next, a part of the semiconductor laminate provided on the main surface 21a of the semiconductor substrate 21 is etched to expose a part of the main surface 21a of the semiconductor substrate 21, thereby obtaining a cross-sectional structure indicated by an arrow (a) in FIG. 41. At this time, the width of the remaining semiconductor laminate is about 500 μm, and the exposed area becomes the installation area of ​​the first electrode 27. When the installation area of ​​the first electrode 27 is secured by etching, the semiconductor laminate remaining on the main surface 21a of the semiconductor substrate 21 and the exposed area are coated with an insulating layer 290 such as SiN. Next, after a part of the insulating layer 290 located in the installation area of ​​the first electrode 27 and the second electrode 28 is removed, Au plating is applied, and the first electrode 27 and the second electrode 28 are patterned. After Au plating, the main surface 21a may be planarized by CMP (Chemical Mechanical Planarization) if necessary. Therefore, the first electrode 27 provided on the main surface 21a and the second electrode 28 provided on the contact layer 26 side of the semiconductor laminate are insulated via the insulating layer 290. Through this process, the cross-sectional structure indicated by the arrow (b) in FIG.

[0163] As described above, since the first electrode 27 and the second electrode 28 are disposed on the main surface 21a side of the semiconductor substrate 21, a SiN single layer or a dielectric multilayer film is directly formed as the first light confinement layer 130 on the back surface 21b of the semiconductor substrate 21, thereby obtaining a cross-sectional structure indicated by the arrow (c) in FIG. 41. Note that the ratio of thicknesses of the various parts of the pump light source 200A (the illustrated pump light source 200A) indicated by the arrow (c) differs from the ratio of thicknesses of the various parts in an actually manufactured device, but the overall thickness of the pump light source 200A is at most about 100 μm to 150 μm. Also, on the main surface 21a of the semiconductor substrate 21, the first electrode 27 has a shape surrounding the second electrode 28.

[0164] When the excitation light source 200A is obtained through the manufacturing process shown in Fig. 41, the excitation light source 200A is epitaxially mounted on a main surface 500a of a 2 mm × 2.5 mm submount 500 as shown in Fig. 42(a). An n-electrode pad 520 to be electrically connected to the first electrode 27 and a p-electrode pad 510 to be electrically connected to the second electrode 28 are printed in advance on the main surface 500a of the prepared submount 500. When the excitation light source 200A is fixed to the submount 500, spacers 550a to 550d made of an insulating material are also fixed to the main surface 500a of the submount 500 so as to surround the excitation light source 200A.

[0165] On the other hand, when manufacturing the optical device 100A, as shown in FIG. 43(a), first, a substrate 15 having optical transparency is prepared. Note that, for the substrate 15 to be prepared, a sufficiently large quartz plate is used since only the flat central portion of the laminated portion is used. First, a second optical confinement layer 140 having a single-layer structure made of SiN, TiO2, etc. is provided on one surface of the substrate 15. Furthermore, a PC layer 120 consisting of a basic layer and a plurality of modified refractive index areas is provided on the second optical confinement layer 140. After an ultraviolet curing resin (UC layer 11) containing an upconversion material as a main ingredient is applied by spin coating on the PC layer 120, the UC layer 11 is UV cured. Note that flatness and parallelism are very important in manufacturing the UC layer 11. In particular, when an ultraviolet curing resin (containing an upconversion material as a main ingredient) is applied by spin coating, flatness at the end portion cannot be obtained. Therefore, as shown in FIG. 43(b), the central portion on the substrate 15 (the area where the laminated portion is flat) is used, and by cutting the laminated body including the substrate 15 to a width of 2 mm, an optical device 100A of approximately 2 mm x 2 mm (the first optical confinement layer 130 is formed on the excitation light source 200A side) is obtained.

[0166] The optical device 100A obtained as described above is mounted on the submount 500 via spacers 550a to 550d, with the UC layer 11 in direct contact with the first optical confinement layer 130 on the side of the excitation light source 200A mounted epitaxially down on the submount 500, as shown in FIG. 43(c).

[0167] As described above, Fig. 44(a) is a plan view of a light-emitting device manufactured by the first manufacturing method (unit assembly type) in which units (excitation light source 200A and optical device 100A) constituting the light-emitting device according to the fourth embodiment are manufactured separately and then assembled, and Fig. 44(b) is a cross-sectional view of the light-emitting device taken along the line indicated by arrow II in Fig. 44(a). Components such as a dichroic mirror are not shown in Fig. 44(b).

[0168] Fig. 45(a) is a cross-sectional view of a light-emitting device having a first-structure light confinement layer manufactured by the above-mentioned unit assembly type manufacturing method (first manufacturing method). The light-emitting device of Fig. 45(a) according to the fourth embodiment includes an excitation light source 200A and an optical device 100C abutted against the excitation light source 200A via the first light confinement layer 130.

[0169] In the example shown in FIG. 45(a), the excitation light source 200A can be replaced with the excitation light sources 20A to 20C of the above-mentioned first to third embodiments and first to tenth modified examples, and the basic configuration has a cross-sectional structure indicated by the arrow (c) in FIG. That is, the excitation light source 200A includes a semiconductor substrate 21 made of GaAs, a first cladding layer 24 provided on a principal surface 21a of the semiconductor substrate 21, an active layer 22 provided on the first cladding layer 24, a PC layer 23 (which may be a phase modulation layer) provided on the active layer 22, a second cladding layer 25 provided on the PC layer 23, a contact layer 26 provided on the second cladding layer 25, a second electrode 28 provided on the contact layer 26, a first electrode 27 provided in an exposed region of the principal surface 21a of the semiconductor substrate 21 that is not covered by the semiconductor laminate including the active layer 22 and the PC layer 23, and an insulating layer 290 made of SiN or the like that covers the principal surface 21a and the surface of the semiconductor laminate except for the first electrode 27 and the second electrode 28. The PC layer 23 is composed of a basic layer 23a made of GaAs and a plurality of modified refractive index regions 23b defined by holes provided in the basic layer 23a.

[0170] On the other hand, the optical device 100C is mounted on the above-mentioned excitation light source 200A (on the back surface 21b of the semiconductor substrate 21) via a first optical confinement layer 130 (which may have a single-layer structure made of SiN, TiO2, etc.) made of a dielectric multilayer film. The optical device 100C includes a substrate 15 having optical transparency, a second optical confinement layer 140 having a first structure provided on one surface of the substrate 15, a PC layer 120 (which may be a phase modulation layer) embedded inside or in a surface region of the second optical confinement layer 140, a UC layer 11 sandwiched between the PC layer 120 and the first optical confinement layer 130, and the first optical confinement layer 130.

[0171] In this optical device 100C, the second light confinement layer 140 has a base 141 and a cover layer 142, each of which has a single-layer structure made of SiN or TiO2. The PC layer 120 is located between the base 141 and the cover layer 142, and includes a base layer 120a and a plurality of modified refractive index areas 120b. The base layer 120a also has a single-layer structure made of SiN or TiO2. The multiple modified refractive index areas of the PC layer 120 are voids. The cover layer 142 also has a single-layer structure made of SiN or TiO2. Here, when the base 141 and the base layer 120a of the PC layer 120 are made of different materials (for example, when the base 141 is made of SiN and the base layer 12a is made of TiO2), the configuration of this optical device 100C substantially corresponds to the configuration of the optical device 100A indicated by the arrow (a) in FIG. 40. On the other hand, when the base 141, the base layer 120a of the PC layer 120, and the cover layer 142 are made of the same material (for example, when each is made of SiN), the configuration of the optical device 100C substantially corresponds to the configuration of the optical device 100B shown by the arrow (b) in Fig. 40. That is, a structure in which the PC layer 120 is embedded inside the second optical confinement layer 140 having a single-layer structure can be realized.

[0172] According to the light-emitting device (fourth embodiment in which the second optical confinement layer 140 has the first structure) obtained by the above-mentioned unit assembly type manufacturing method (first manufacturing method), unnecessary heat is not applied to the UC layer 11 provided on the substrate 15. Moreover, the multiple modified refractive index areas 120b (voids) provided in the PC layer 120 are not filled with the upconversion material. Furthermore, it is also possible to measure the initial optical characteristics of only the photonic crystal surface-emitting laser before mounting the optical device 100C on the excitation light source 200A.

[0173] Fig. 45(b) is a cross-sectional view of a light-emitting device having an optical confinement layer of the second structure manufactured by the above-mentioned unit assembly type manufacturing method (first manufacturing method). The light-emitting device of Fig. 45(b) according to the fourth embodiment includes an excitation light source 200A and an optical device 100D abutted against the excitation light source 200A via a first optical confinement layer 130. The light-emitting device of Fig. 45(b) has a similar structure to the light-emitting device of Fig. 45(a) except that the optical device 100D has a PC layer 120 of the second structure.

[0174] That is, the optical device 100D is mounted on the excitation light source 200A (on the back surface 21b of the semiconductor substrate 21) via a first optical confinement layer 130 (which may have a single-layer structure made of SiN, TiO2, etc.) made of a dielectric multilayer film. The optical device 100D includes a substrate 15 having optical transparency, a second optical confinement layer 140 having a second structure provided on one surface of the substrate 15, a PC layer 120 (which may be a phase modulation layer) embedded in a surface region of the second optical confinement layer 140, a UC layer 11 sandwiched between the PC layer 120 and the first optical confinement layer 130, and the first optical confinement layer 130.

[0175] In this optical device 100D, the second optical confinement layer 140 has a base 141 having a single-layer structure made of SiN and a cover layer 142 having a single-layer structure made of TiO2. The PC layer 120 is located between the base 141 and the cover layer 142, and includes a base layer 120a and a plurality of modified refractive index areas 120b. The base layer 120a also has a single-layer structure made of SiN, and substantially constitutes a part of the second optical confinement layer 140. The multiple modified refractive index areas 120b of the PC layer 120 are defined by multiple recesses provided in the base layer 120a that constitutes a part of the second optical confinement layer 140, and these multiple recesses are filled with the same TiO2 material as the material of the cover layer 142. Here, when the base 141 and the basic layer 120a of the PC layer 120 are made of different materials (for example, when the base 141 is made of SiN and the basic layer 12a is made of TiO2), the configuration of this optical device 100D substantially corresponds to the configuration of the optical device 100A shown by the arrow (a) in FIG. 40. In this case, the basic layer 120a and the multiple modified refractive index areas 120b are made of the same material, but the refractive index of the basic layer 120a is different from the refractive index of the multiple modified refractive index areas 120b. On the other hand, when the base 141 and the basic layer 120a of the PC layer 120 are made of the same material (for example, when both are made of SiN), the configuration of this optical device 100D substantially corresponds to the configuration of the optical device 100B shown by the arrow (b) in FIG. 40. That is, a structure in which the PC layer 120 is embedded in the surface region of the second optical confinement layer 140 having a single-layer structure can be realized.

[0176] The light emitting device shown in FIG. 45(b) (the fourth embodiment in which the second optical confinement layer 140 has the second structure) also provides the same effects as the light emitting device shown in FIG. 45(a).

[0177] Fig. 46(a) is a cross-sectional view of a light-emitting device having an optical confinement layer of the third structure manufactured by the above-mentioned unit assembly type manufacturing method (first manufacturing method). The light-emitting device of Fig. 46(a) according to the fourth embodiment includes an excitation light source 200A and an optical device 100E abutted against the excitation light source 200A via a first optical confinement layer 130. The light-emitting device of Fig. 46(a) has a similar structure to the light-emitting device of Fig. 45(a) except that the optical device 100E has a PC layer 120 of the third structure.

[0178] That is, the optical device 100E is mounted on the excitation light source 200A (on the back surface 21b of the semiconductor substrate 21) via a first optical confinement layer 130 (which may have a single-layer structure made of SiN, TiO2, etc.) made of a dielectric multilayer film. The optical device 100E includes a substrate 15 having optical transparency, a second optical confinement layer 140 having a third structure provided on one surface of the substrate 15, a PC layer 120 (which may be a phase modulation layer) embedded in a surface region of the second optical confinement layer 140, a UC layer 11 sandwiched between the PC layer 120 and the first optical confinement layer 130, and the first optical confinement layer 130.

[0179] In this optical device 100E, the second optical confinement layer 140 has a single-layer structure made of SiN, and a plurality of recesses are formed on the surface of the second optical confinement layer 140 to define a plurality of modified refractive index areas 120b of the PC layer 120. Therefore, the surface region of the second optical confinement layer 140 in which the plurality of recesses are formed becomes the basic layer 120a of the PC layer 120. In addition, in the PC layer 120 of this third structure, the surface of the second optical confinement layer 140 and the inner walls (including the bottoms) of the plurality of recesses are covered with a cover layer 120c made of TiO2. The optical device 100E having the PC layer 120 of this third structure substantially corresponds to the configuration of the optical device 100B indicated by the arrow (b) in FIG. 40. That is, a structure in which the PC layer 120 is embedded in the surface region of the second optical confinement layer 140 having a single-layer structure can be realized.

[0180] The light emitting device shown in FIG. 46(a) (the fourth embodiment in which the second optical confinement layer 140 has the second structure) also provides the same effects as the light emitting device shown in FIG. 45(a).

[0181] Fig. 46(b) is a cross-sectional view of a light-emitting device having an optical confinement layer of the fourth structure, manufactured by the above-mentioned unit assembly type manufacturing method (first manufacturing method). The light-emitting device of Fig. 46(b) according to the fourth embodiment includes an excitation light source 200A and an optical device 100E abutted against the excitation light source 200A via a first optical confinement layer 130. The light-emitting device of Fig. 46(b) has a similar structure to the light-emitting device of Fig. 45(a), except that the optical device 100E has a PC layer 120 of the fourth structure.

[0182] That is, the optical device 100F is mounted on the excitation light source 200A (on the back surface 21b of the semiconductor substrate 21) via a first optical confinement layer 130 (which may have a single-layer structure made of SiN, TiO2, etc.) made of a dielectric multilayer film. The optical device 100F includes a substrate 15 having optical transparency, a second optical confinement layer 140 having a fourth structure provided on one surface of the substrate 15, a PC layer 120 (which may be a phase modulation layer) embedded in a surface region of the second optical confinement layer 140, a UC layer 11 sandwiched between the PC layer 120 and the first optical confinement layer 130, and the first optical confinement layer 130.

[0183] In this optical device 100F, the second optical confinement layer 140 has a single-layer structure made of SiN, and a plurality of recesses are formed on the surface of the second optical confinement layer 140 to define a plurality of modified refractive index areas 120b of the PC layer 120. Therefore, the surface region of the second optical confinement layer 140 in which the plurality of recesses are formed becomes the basic layer 120a of the PC layer 120. In addition, in the PC layer 120 of this fourth structure, the surface of the second optical confinement layer 140 and the inner walls (including the bottoms) of the plurality of recesses are directly covered with the UC layer 11, and each of the plurality of recesses is filled with a part of the UC layer 11. The optical device 100F having the PC layer 120 of this fourth structure substantially corresponds to the configuration of the optical device 100B indicated by the arrow (b) in FIG. 40. That is, a structure in which the PC layer 120 is embedded in the surface region of the second optical confinement layer 140 having a single-layer structure can be realized.

[0184] The light emitting device shown in FIG. 46(b) (the fourth embodiment in which the second optical confinement layer 140 has the second structure) also provides the same effects as the light emitting device shown in FIG. 45(a).

[0185] Next, a resonator structure that is easy to oscillate will be considered. FIG. 47 is a diagram for explaining a design guideline for an optical device (a resonator part model including a second light confinement layer 140 and a PC layer 120). The model 100G shown in FIG. 47 has a structure in which a laminate consisting of a PC layer 120 (which may be a phase modulation layer), a second light confinement layer 140, and a UC layer 11 is sandwiched between a pair of quartz plates 151 and 152. The quartz plates 151 and 152 each have a refractive index of 1.46 for light with a wavelength of 550 nm. The UC layer 11 has a refractive index of 1.5 for light with a wavelength of 550 nm. The second light confinement layer 140 is made of SiN and has a refractive index of 2.0 for light with a wavelength of 550 nm. The basic layer 120a of the PC layer 120 is made of TiO2, and the multiple modified refractive index areas 120b are holes provided in the basic layer 120a. Moreover, the occupancy rate (hereinafter, referred to as "FF (Filling Factor)") of the actual modified refractive index area 120b with respect to the area where one modified refractive index area 120b can be installed on the surface of the base layer 120a is 30%.

[0186] The first condition for designing a resonator structure that is easy to oscillate is the distribution ratio Γ of light distributed in the UC layer 11. UC In order to satisfy the first condition, it is necessary to design an appropriate layer structure while keeping in mind that light has a tendency to be localized in a layer with a high refractive index and to move away from a layer with a low refractive index. The second condition is to increase the light confinement strength within the resonator portion, that is, the diffraction strength κ in the PC layer 120. 2,0 The diffraction intensity κ m,n (cm -1 ) is expressed by the following formula (23):

number

[0187] From the above formula (23), the optical confinement strength of the resonator is increased (the diffraction strength κ2,0 In order to increase Γ PC , increasing the difference in refractive index between the inside and the peripheral area of ​​the PC layer 120, and increasing the Fourier coefficient F 2,0 In this case, if it is kept in mind that light moves away from the layer with a low refractive index, it may be better to fill the inside of each modified refractive index area 120b with another material rather than filling it with air with a low refractive index.

[0188] As a result of the above considerations, specifically, it is preferable to set the refractive index of the PC layer 120 higher than the refractive index of the surrounding area. Furthermore, the dielectric constant difference (ε in- ε out It was found that an embedded PC layer structure, such as modified refractive index area 120b in which TiO2 is embedded in holes formed in base layer 120a made of SiN, is preferable so that there is a difference between the refractive indexes of the two layers. Therefore, in order to examine the conditions in more detail, a study will be made using Figures 48, 49(a) to 49(e), 50(a) to 50(f), 51, and 52(a) to 52(e).

[0189] Fig. 48 is a graph showing the relationship between the Fourier coefficient and the FF value for various hole shapes in the PC layer of the optical device having the cross-sectional structure shown in Fig. 47. The prepared hole shapes (planar shapes of the modified refractive index area 120b provided in the base layer 120a) are a perfect circle (pattern 1), a square (pattern 2), an equilateral triangle (pattern 3), and a right-angled isosceles triangle (pattern 4).

[0190] FIG. 48 shows the Fourier coefficients F 2,0 (180° diffraction) and F 1,0 The relationship between the magnitude of the Fourier coefficient F (90° diffraction) and the FF value is shown. 2,0does not approach 0, it can be seen that the planar shape of the modified refractive index area 120b is preferably a right-angled isosceles triangle with FF 30%. The following calculations are mainly performed for the case where the planar shape of the modified refractive index area 120b is a right-angled isosceles triangle with FF 30%.

[0191] 49(a) to 49(e) are diagrams showing specific structural conditions for a resonator structure that is easy to oscillate, based on the above-mentioned study results. 2,0 FIG. 49(b) shows an example of a cross-sectional structure of an optical device (a resonator part model including the second optical confinement layer 140 and the PC layer 120) that can increase the distribution ratio Γ UC FIG. 49(c) shows an example of the cross-sectional structure of an optical device (a resonator part model including the second optical confinement layer 140 and the PC layer 120) that can increase the distribution ratio of light present in the UC layer 11. The diffraction intensity κ 2,0 and distribution ratio Γ UC 49(d) and 49(e) are diagrams for explaining the hole shapes applied to the calculation.

[0192] FIG. 49(a) shows a cross-sectional structure of a model 100H having a structure (structure I) for increasing the diffraction intensity. This model 100H is composed of a quartz plate 151, a PC layer 120 (which may be a phase modulation layer) having a thickness of 200 nm provided on the quartz plate 151, a second optical confinement layer 140 having a thickness of 200 nm provided on the PC layer 120, and a UC layer 11 having a thickness of 2 μm provided on the second optical confinement layer 140. The quartz plate 151 has a refractive index of 1.46 for light having a wavelength of 550 nm. The UC layer 11 has a refractive index of 1.5 for light having a wavelength of 550 nm. The second optical confinement layer 140 is made of SiN and has a refractive index of 2.0 for light having a wavelength of 550 nm. The basic layer 120a of the PC layer 120 is made of TiO2, and the multiple modified refractive index areas 120b are holes provided in the basic layer 120a. The planar shapes of the modified refractive index areas 120b prepared are pattern 1 (a perfect circle) with FF=10% shown in Figure 49(d) and pattern 4 (a right-angled isosceles triangle) with FF=30% shown in Figure 49(e).

[0193] On the other hand, FIG. 49(b) shows the distribution ratio (Γ UC ) is shown. This model 100I is composed of a quartz plate 151, a PC layer 120 (which may be a phase modulation layer) having a thickness of 100 nm provided on the quartz plate 151, a second optical confinement layer 140 having a thickness of 100 nm provided on the PC layer 120, and a UC layer 11 having a thickness of 2 μm provided on the second optical confinement layer 140. The quartz plate 151 has a refractive index of 1.46 for light with a wavelength of 550 nm. The UC layer 11 has a refractive index of 1.5 for light with a wavelength of 550 nm. The second optical confinement layer 140 is made of SiN and has a refractive index of 2.0 for light with a wavelength of 550 nm. The basic layer 120a of the PC layer 120 is made of SiN (the refractive index for light with a wavelength of 550 nm is 2.0), and the multiple modified refractive index areas 120b are holes provided in the basic layer 120a. The planar shapes of the prepared modified refractive index areas 120b are, similarly to FIG. 49(a), pattern 1 with FF=10% (see FIG. 49(d)) and pattern 4 with FF=30% (see FIG. 49(e)).

[0194] As can be seen from the table in FIG. 49(c), the distribution ratio Γ of light present in the UC layer 11 UC is higher for model 100I having structure II. 2,0 The diffraction intensity κ of the model 100H having the structure I is larger for both the pattern 1 and the pattern 2. In both the model 100H having the structure I and the model 100I having the structure II, the diffraction intensity κ of the model 100H having the structure I is larger for the pattern 4 than for the pattern 1. 2,0 is getting bigger.

[0195] 50(a) to 50(f) are diagrams showing calculation results of the thickness dependency of the UC layer 11. FIG. 50(a) shows an example of the cross-sectional structure of a prepared optical device (a resonator part model including the second optical confinement layer 140 and the PC layer 120), and FIG. 50(b) shows the hole shape applied to the calculation. FIG. 50(c) to FIG. 50(f) show the diffraction intensity κ 2,0 , distribution proportion Γ PC (proportion of light present in the PC layer), distribution ratio Γ UC and the effective refractive index n eff 13 is a table showing the respective calculation results.

[0196] The model 100J shown in FIG. 50(a) has a structure in which a laminate composed of a PC layer 120, a second light confinement layer 140, and a UC layer 11 is sandwiched between a pair of quartz plates 151 and 152. The quartz plates 151 and 152 each have a refractive index of 1.46 for light with a wavelength of 550 nm. The UC layer 11 has a refractive index of 1.5 for light with a wavelength of 550 nm, and has a thickness of 20 nm to 2 μm. The second light confinement layer 140 is made of TiO2 and has a refractive index of 2.5 for light with a wavelength of 550 nm. The second light confinement layer 140 has a thickness of 10 nm. The base layer 120a of the PC layer 120 is made of SiN and has a refractive index of 2.0 for light with a wavelength of 550 nm. The multiple modified refractive index areas 120b are obtained by filling holes provided in the base layer 120a with TiO2. Moreover, the planar shape of the modified refractive index area 120b in the PC layer 120 is a right-angled isosceles triangle as shown in FIG. 50(b), and the FF is 30%.

[0197] FIG. 50(c) shows the diffraction intensity κ for combinations of the PC layer 120 having a thickness of 30 nm, 50 nm, and 100 nm and the UC layer 11 having a thickness of 50 nm, 100 nm, 200 nm, 500 nm, 1000 nm, and 2000 nm. 2,0 50(d) shows the distribution ratio Γ for combinations of the PC layer 120 having a thickness of 30 nm, 50 nm, and 100 nm and the UC layer 11 having a thickness of 50 nm, 100 nm, 200 nm, 500 nm, 1000 nm, and 2000 nm. PC 50(e) shows the distribution ratio Γ for combinations of the PC layer 120 having a thickness of 30 nm, 50 nm, and 100 nm and the UC layer 11 having a thickness of 50 nm, 100 nm, 200 nm, 500 nm, 1000 nm, and 2000 nm. UC 50(f) shows the calculation results of the effective refractive index (equivalent refractive index) n eff The calculation results are shown.

[0198] From the results of FIGS. 50(c) to 50(f), it is understood that the UC layer 11 is particularly unlikely to be affected by thickness variations if it has a thickness of 200 nm or more.

[0199] Fig. 51 is a table summarizing the dependence of the thickness of the optical confinement layer (second optical confinement layer 140) on the thickness of the PC layer 120 for an optical device having the cross-sectional structure shown in Fig. 50(a). In particular, the upper part of Fig. 51 shows the diffraction intensity κ for combinations of TiO2 layers (second optical confinement layer 140) having thicknesses of 0 nm, 5 nm, 10 nm, 20 nm, 30 nm, 50 nm, and 100 nm and PC layers 120 having thicknesses of 10 nm, 20 nm, 30 nm, 50 nm, and 100 nm. 2,0 (cm -151 shows the calculation results of the distribution ratio Γ for combinations of TiO2 layers (second optical confinement layer 140) having thicknesses of 0 nm, 5 nm, 10 nm, 20 nm, 30 nm, 50 nm, and 100 nm and PC layers 120 having thicknesses of 10 nm, 20 nm, 30 nm, 50 nm, and 100 nm. UC The calculation results are shown.

[0200] From the calculation results in Figure 51, the diffraction intensity κ 2,0 and distribution ratio Γ UC In other words, the optimum range in which both the diffraction intensity κ 2,0 is 1000(cm -1 ) and the distribution ratio Γ UC The range in which the optical transmittance becomes 40% is when the thickness of the PC layer 120 is 30 nm to 50 nm and the thickness of the TiO2 layer (second optical confinement layer 140) provided directly on the PC layer 120 is 0 nm to 10 nm. In Fig. 51, this optimal range is surrounded by a solid line.

[0201] Furthermore, for an optical device having the optical confinement layer 140 of the fourth structure, the optimum range of the thickness of the optical confinement layer 140 and the thickness of the PC layer 120 (phase modulation layer) will be examined. Fig. 52(a) shows an example of the cross-sectional structure of an optical device (a resonator part model including the second optical confinement layer 140 and the PC layer 120) prepared for the examination, and Figs. 52(b) to 52(e) show the diffraction intensity κ 2,0 , distribution proportion Γ PC (proportion of light present in the PC layer), distribution ratio Γ UC and the effective refractive index n eff 52(b) to 52(e) show various calculation results as the relationship between the "thickness of the optical confinement layer" and the "thickness of the phase modulation layer", but essentially they mean the "thickness of the optical confinement layer" and the "thickness of the PC layer".

[0202] The model 100K shown in FIG. 52(a) is composed of a quartz plate 151, a second optical confinement layer 140 (with a PC layer 120 embedded in the surface region) having a thickness of 50 nm to 200 nm provided on the quartz plate 151, and a UC layer 11 having a thickness of 2 μm provided on the second optical confinement layer 140. The base layer 120a of the PC layer 120 is the surface region of the second optical confinement layer 140, and a plurality of recesses are provided on the surface of the second optical confinement layer 140 as a plurality of modified refractive index areas 120b. The quartz plate 151 has a refractive index of 1.46 for light with a wavelength of 550 nm. The UC layer 11 has a refractive index of 1.5 for light with a wavelength of 550 nm. The second optical confinement layer 140 is made of TiO2 and has a refractive index of 2.5 for light with a wavelength of 550 nm. The base layer 120a of the PC layer 120 is a surface region of the second light confinement layer 140, and each recess defining each of the multiple modified refractive index areas 120b is filled with a part of the ultraviolet curable resin that constitutes the UC layer 11. Furthermore, the planar shape of each modified refractive index area 120b in the PC layer 120 is a right-angled triangle, and the FF is 30%.

[0203] FIG. 52(b) shows the diffraction intensity κ for combinations of the second optical confinement layer 140 having a thickness of 50 nm, 100 nm, and 200 nm and the PC layer 120 (phase modulation layer) having a thickness of 10 nm, 20 nm, 50 nm, 100 nm, 150 nm, and 200 nm. 2,0 52(c) shows the distribution ratio Γ for combinations of the second optical confinement layer 140 having a thickness of 50 nm, 100 nm, and 200 nm and the PC layer 120 (phase modulation layer) having a thickness of 10 nm, 20 nm, 50 nm, 100 nm, 150 nm, and 200 nm. PC 52(d) shows the distribution ratio Γ for combinations of the second optical confinement layer 140 having a thickness of 50 nm, 100 nm, and 200 nm and the PC layer 120 (phase modulation layer) having a thickness of 10 nm, 20 nm, 50 nm, 100 nm, 150 nm, and 200 nm. UC52(e) shows the calculation results of the effective refractive index (equivalent refractive index) n eff The calculation results are shown.

[0204] 52(b) to 52(e), the region surrounded by the solid line is the optimum range. That is, the thickness of the second optical confinement layer 140 is preferably in the range of 50 nm to 100 nm, and the thickness of the PC layer 120 (phase modulation layer) is preferably 50 nm.

[0205] Fig. 53(a) is a cross-sectional view of a light-emitting device having a first-structure light confinement layer manufactured by the upconversion material injection type manufacturing method (second manufacturing method) of the light-emitting device according to the fourth embodiment. Note that Fig. 53(a) shows the state before each part is cut along the cutting lines Sa and Sb.

[0206] The second manufacturing process includes, as a manufacturing process of the UC layer 11, a step of injecting an ultraviolet curable resin (containing an upconversion material as a main material) constituting the UC layer 11. In this respect, it differs from the above-mentioned first manufacturing method in which the excitation light source 200A and the optical devices 100C-100F are manufactured as separate units and these units are finally assembled. That is, in the second manufacturing method, the optical devices 100C-100F common to the multiple excitation light sources 200A are prepared, and finally, the light-emitting device shown in FIG. 45(a) is obtained by cutting the completed product along the cutting lines Sa and Sb(a) shown in FIG. 53(a).

[0207] 53(a) (before cutting), a plurality of excitation light sources 200A are provided for a common optical device 100C. Each excitation light source 200A can be replaced with the excitation light sources 20A-20C of the above-mentioned first to third embodiments and first to tenth modified examples, and the basic configuration has a cross-sectional structure indicated by the arrow (c) in FIG. That is, each excitation light source 200A includes a semiconductor substrate 21 made of GaAs, a first cladding layer 24 provided on a principal surface 21a of the semiconductor substrate 21, an active layer 22 provided on the first cladding layer 24, a PC layer 23 provided on the active layer 22, a second cladding layer 25 provided on the PC layer 23, a contact layer 26 provided on the second cladding layer 25, a second electrode 28 provided on the contact layer 26, a first electrode 27 provided in an exposed region of the principal surface 21a of the semiconductor substrate 21 that is not covered by the semiconductor laminate including the active layer 22 and the PC layer 23, and an insulating layer 290 made of SiN or the like that covers the principal surface 21a and the surface of the semiconductor laminate except for the first electrode 27 and the second electrode 28. The PC layer 23 is composed of a basic layer 23a made of GaAs and a plurality of modified refractive index regions 23b defined by holes provided in the basic layer 23a.

[0208] On the other hand, the common optical device 100C is mounted on the above-mentioned excitation light source 200A (on the back surface 21b of the semiconductor substrate 21) via a first optical confinement layer 130 (which may have a single-layer structure made of SiN, TiO2, etc.) made of a dielectric multilayer film. This common optical device 100C includes a substrate 15 having optical transparency, a second optical confinement layer 140 having a first structure provided on one surface of the substrate 15, a PC layer 120 (which may be a phase modulation layer) embedded inside or in the surface region of the second optical confinement layer 140, a UC layer 11 sandwiched between the PC layer 120 and the first optical confinement layer 130, and the first optical confinement layer 130. In particular, since an ultraviolet curing resin constituting the UC layer 11 is injected between the PC layer 120 and the first optical confinement layer 130, a spacer 110 (an ultraviolet curing resin in which a plurality of beads are dispersed) is disposed to prevent leakage of the ultraviolet curing resin and to define the thickness of the UC layer 11. In addition, a partition member 111 made of ultraviolet curing resin is placed in this space to suppress shrinkage near the center of the UC layer 11 after UV curing (to suppress thickness fluctuation of the UC layer 11 based on the first optical confinement layer 130).

[0209] In this optical device 100C, the second light confinement layer 140 has a base 141 and a cover layer 142, each of which has a single-layer structure made of SiN or TiO2. The PC layer 120 is located between the base 141 and the cover layer 142, and includes a base layer 120a and a plurality of modified refractive index areas 120b. The base layer 120a also has a single-layer structure made of SiN or TiO2. The multiple modified refractive index areas of the PC layer 120 are voids. The cover layer 142 also has a single-layer structure made of SiN or TiO2. Here, when the base 141 and the base layer 120a of the PC layer 120 are made of different materials (for example, when the base 141 is made of SiN and the base layer 12a is made of TiO2), the configuration of this optical device 100C substantially corresponds to the configuration of the optical device 100A indicated by the arrow (a) in FIG. 40. On the other hand, when the base 141, the base layer 120a of the PC layer 120, and the cover layer 142 are made of the same material (for example, when each is made of SiN), the configuration of the optical device 100C substantially corresponds to the configuration of the optical device 100B shown by the arrow (b) in Fig. 40. That is, a structure in which the PC layer 120 is embedded inside the second optical confinement layer 140 having a single-layer structure can be realized.

[0210] According to the light-emitting device obtained by the above-mentioned upconversion material injection type manufacturing method (second manufacturing method), particularly the individual light-emitting devices cut along the cutting lines Sa and Sb (fourth embodiment in which the second optical confinement layer 140 has the first structure), unnecessary heat is not applied to the UC layer 11 provided on the substrate 15. Moreover, the multiple modified refractive index areas 120b (voids) provided in the PC layer 120 are not filled with the upconversion material. Furthermore, it is also possible to measure the initial optical characteristics of only the photonic crystal surface-emitting laser before mounting the optical device 100C on the excitation light source 200A.

[0211] Furthermore, according to the second manufacturing method, a large number of light-emitting devices having the same structure can be obtained by manufacturing the devices once, and the size of each device can be reduced. In addition, the thickness of the UC layer 11 is defined by the spacer 110, so that the thickness can be controlled with high precision. Since the thickness of the UC layer 11 can be controlled with high precision, the thickness of the UC layer 11 can be optimized, and the generation of unnecessary longitudinal modes can be effectively suppressed. Furthermore, the UC layer 11 can be manufactured parallel to other layers such as the substrate 15, so that the waveguide loss of the visible in-plane resonance mode can also be suppressed.

[0212] Fig. 53(b) is a cross-sectional view of a light-emitting device having an optical confinement layer of the second structure manufactured by the second manufacturing method, in which the state before each part is cut along the cutting lines Sa and Sb is also shown.

[0213] The light-emitting device in Fig. 53(b) (before cutting) includes a plurality of pump light sources 200A and a common optical device 100D abutted against the pump light sources 200A via the first optical confinement layer 130. The light-emitting device shown in Fig. 53(b) has a similar structure to the light-emitting device in Fig. 53(a) except that the common optical device 100D has a PC layer 120 of the second structure.

[0214] That is, the common optical device 100D is mounted on the multiple excitation light sources 200A (on the back surface 21b of the semiconductor substrate 21) via a first optical confinement layer 130 (which may have a single-layer structure made of SiN, TiO2, etc.) made of a dielectric multilayer film. The common optical device 100D includes a substrate 15 having optical transparency, a second optical confinement layer 140 having a second structure provided on one surface of the substrate 15, a PC layer 120 (which may be a phase modulation layer) embedded in a surface region of the second optical confinement layer 140, a UC layer 11 sandwiched between the PC layer 120 and the first optical confinement layer 130, and the first optical confinement layer 130.

[0215] In this common optical device 100D, the second optical confinement layer 140 has a base 141 having a single-layer structure made of SiN and a cover layer 142 having a single-layer structure made of TiO2. The PC layer 120 is located between the base 141 and the cover layer 142, and includes a base layer 120a and a plurality of modified refractive index areas 120b. The base layer 120a also has a single-layer structure made of SiN, and substantially constitutes a part of the second optical confinement layer 140. The plurality of modified refractive index areas of the PC layer 120 are defined by a plurality of recesses provided in the base layer 120a that constitutes a part of the second optical confinement layer 140, and these recesses are filled with the same TiO2 material as the material of the cover layer 142. In particular, since the ultraviolet curing resin that constitutes the UC layer 11 is injected between the PC layer 120 and the first optical confinement layer 130, a spacer 110 is arranged to prevent leakage of the ultraviolet curing resin and to define the thickness of the UC layer 11. In addition, a partition member 111 made of ultraviolet curing resin is placed in this space to suppress shrinkage near the center of the UC layer 11 after UV curing (to suppress thickness fluctuation of the UC layer 11 based on the first optical confinement layer 130).

[0216] Here, when the base 141 and the basic layer 120a of the PC layer 120 are made of different materials (for example, when the base 141 is made of SiN and the basic layer 12a is made of TiO2), the configuration of this common optical device 100D substantially corresponds to the configuration of the optical device 100A shown by the arrow (a) in FIG. 40. In this case, the basic layer 120a and the multiple modified refractive index areas 120b are made of the same material, but the refractive index of the basic layer 120a is different from the refractive index of the multiple modified refractive index areas 120b. On the other hand, when the base 141 and the basic layer 120a of the PC layer 120 are made of the same material (for example, when both are made of SiN), the configuration of this common optical device 100D substantially corresponds to the configuration of the optical device 100B shown by the arrow (b) in FIG. 40. That is, a structure in which the PC layer 120 is embedded in the surface region of the second optical confinement layer 140 having a single-layer structure can be realized.

[0217] The light emitting device shown in Fig. 53(b), particularly each light emitting device after cutting (fourth embodiment in which the second optical confinement layer 140 has the second structure), also provides the same effect as the light emitting device shown in Fig. 45(a). In addition, the manufacturing method for obtaining the light emitting device shown in Fig. 53(b) also provides the same effect as the manufacturing method for obtaining the light emitting device shown in Fig. 53(a) described above.

[0218] Fig. 54(a) is a cross-sectional view of a light-emitting device having an optical confinement layer of the third structure manufactured by the second manufacturing method. Note that Fig. 54(a) also shows the state before each part is cut along the cutting lines Sa and Sb.

[0219] The light-emitting device in Fig. 54(a) (before cutting) includes a plurality of pump light sources 200A and a common optical device 100E abutted against the pump light sources 200A via the first optical confinement layer 130. The light-emitting device shown in Fig. 54(a) has a similar structure to the light-emitting device in Fig. 53(a) except that the common optical device 100E has a PC layer 120 of the third structure.

[0220] That is, the common optical device 100E is mounted on the multiple excitation light sources 200A (on the back surface 21b of the semiconductor substrate 21) via a first optical confinement layer 130 (which may have a single-layer structure made of SiN, TiO2, etc.) made of a dielectric multilayer film. The common optical device 100E includes a substrate 15 having optical transparency, a second optical confinement layer 140 having a third structure provided on one surface of the substrate 15, a PC layer 120 (which may be a phase modulation layer) embedded in a surface region of the second optical confinement layer 140, a UC layer 11 sandwiched between the PC layer 120 and the first optical confinement layer 130, and the first optical confinement layer 130.

[0221] In this common optical device 100E, the second light confinement layer 140 has a single-layer structure made of SiN, and a plurality of recesses are formed on the surface of the second light confinement layer 140 to define a plurality of modified refractive index areas 120b of the PC layer 120. Therefore, the surface area of ​​the second light confinement layer 140 in which the plurality of recesses are formed becomes the basic layer 120a of the PC layer 120. In addition, in the PC layer 120 of this third structure, the surface of the second light confinement layer 140 and the inner walls (including the bottoms) of the plurality of recesses are covered with a cover layer 120c made of TiO2. In addition, since the ultraviolet curing resin constituting the UC layer 11 is injected between the PC layer 120 and the first light confinement layer 130, a spacer 110 is arranged to prevent leakage of the ultraviolet curing resin and to define the thickness of the UC layer 11. In addition, a partition member 111 made of ultraviolet curing resin is arranged in this space to suppress contraction near the center of the UC layer 11 after UV curing (suppression of thickness fluctuation of the UC layer 11 based on the first light confinement layer 130).

[0222] The common optical device 100E having the PC layer 120 of this third structure substantially corresponds to the configuration of the optical device 100B shown by the arrow (b) in Fig. 40. That is, a structure in which the PC layer 120 is embedded in the surface region of the second optical confinement layer 140 having a single-layer structure can be realized.

[0223] The light emitting device shown in Fig. 54(a), particularly each light emitting device after cutting (fourth embodiment in which the second optical confinement layer 140 has the second structure), also provides the same effect as the light emitting device shown in Fig. 45(a). In addition, the manufacturing method for obtaining the light emitting device shown in Fig. 53(b) also provides the same effect as the manufacturing method for obtaining the light emitting device shown in Fig. 53(a) described above.

[0224] Fig. 54(b) is a cross-sectional view of a light-emitting device having an optical confinement layer of the fourth structure manufactured by the second manufacturing method. Note that Fig. 54(b) also shows the state before each part is cut along the cutting lines Sa and Sb.

[0225] The light-emitting device in Fig. 54(b) (before cutting) includes a plurality of pump light sources 200A and a common optical device 100F abutted against the pump light sources 200A via the first optical confinement layer 130. The light-emitting device shown in Fig. 54(b) has a similar structure to the light-emitting device in Fig. 53(a) except that the common optical device 100F has a PC layer 120 of the fourth structure.

[0226] That is, the common optical device 100F is mounted on the multiple excitation light sources 200A (on the back surface 21b of the semiconductor substrate 21) via a first optical confinement layer 130 (which may have a single-layer structure made of SiN, TiO2, etc.) made of a dielectric multilayer film. The common optical device 100F includes a substrate 15 having optical transparency, a second optical confinement layer 140 having a fourth structure provided on one surface of the substrate 15, a PC layer 120 (which may be a phase modulation layer) embedded in a surface region of the second optical confinement layer 140, a UC layer 11 sandwiched between the PC layer 120 and the first optical confinement layer 130, and the first optical confinement layer 130.

[0227] In this common optical device 100F, the second optical confinement layer 140 has a single-layer structure made of SiN, and a plurality of recesses are formed on the surface thereof to define a plurality of modified refractive index areas 120b of the PC layer 120. Therefore, the surface region of the second optical confinement layer 140 in which the plurality of recesses are formed becomes the basic layer 120a of the PC layer 120. In addition, in the PC layer 120 of this fourth structure, the surface of the second optical confinement layer 140 and the inner walls (including the bottoms) of the plurality of recesses are directly covered with the UC layer 11, and each of the plurality of recesses is filled with a part of the UC layer 11. In addition, since the ultraviolet curing resin constituting the UC layer 11 is injected between the PC layer 120 and the first optical confinement layer 130, a spacer 110 is arranged to prevent leakage of the ultraviolet curing resin and to define the thickness of the UC layer 11. In addition, a partition member 111 made of ultraviolet curing resin is placed in this space to suppress shrinkage near the center of the UC layer 11 after UV curing (to suppress thickness fluctuation of the UC layer 11 based on the first optical confinement layer 130).

[0228] The common optical device 100F having the PC layer 120 of this fourth structure substantially corresponds to the configuration of the optical device 100B indicated by the arrow (b) in Fig. 40. That is, a structure in which the PC layer 120 is embedded in the surface region of the second optical confinement layer 140 having a single-layer structure can be realized.

[0229] The light emitting device shown in Fig. 54(b), particularly each light emitting device after cutting (fourth embodiment in which the second optical confinement layer 140 has the second structure), also provides the same effect as the light emitting device shown in Fig. 45(a). In addition, the manufacturing method for obtaining the light emitting device shown in Fig. 53(b) also provides the same effect as the manufacturing method for obtaining the light emitting device shown in Fig. 53(a) described above.

[0230] Next, the above-mentioned upconversion material injection type manufacturing method (second manufacturing method) will be described. Figures 55(a) to 58(d) are diagrams for explaining the manufacturing process of a light-emitting device having an optical confinement layer of the third structure shown in Figure 54(a) as an example.

[0231] 55(a), a first cladding layer 24 (n-type cladding layer), an active layer 22, and a basic layer 23a which will become a PC layer 23 are sequentially laminated by MO-CVD on one surface (principal surface 21a) of a prepared GaAs substrate 21. Meanwhile, a dielectric multilayer film (infrared transmitting visible reflecting mirror) is formed on the other surface (rear surface 21b) of the GaAs substrate 21 by evaporation or sputtering.

[0232] When the layer formation on both sides of the GaAs substrate 21 is completed, a plurality of recesses defining a plurality of modified refractive index areas 23b are formed in the base layer 23a of the PC layer 23 by electron beam lithography and dry etching, as shown in Fig. 55(b). Next, in Fig. 55(c), a second cladding layer 25 (p-cladding layer) and a contact layer 26 are sequentially laminated by MO-CVD on the PC layer 23 composed of the base layer 23a and the plurality of modified refractive index areas 23b.

[0233] As shown in Fig. 55(d), the laminated portion provided on the GaAs substrate 21 as described above is patterned into element portions (each of the excitation light sources 200A including a photonic crystal surface emitting laser) by photolithography and wet etching (unnecessary portions between the elements are etched away). After that, as shown in Fig. 56(a), an insulating layer 290 made of SiN is laminated on one surface (principal surface 21a) of the GaAs substrate 21 and the surface of the laminated body by plasma CVD.

[0234] After lamination of the insulating layer 290, a part of the insulating layer 290 located between the elements is removed (patterned) by photolithography and wet etching as shown in FIG. 56(b), and a first electrode 27 (n-electrode) is further deposited by photolithography and vapor deposition. After deposition, the first electrode 27 is alloyed in a hydrogen atmosphere. Then, as shown in FIG. 56(c), a part of the insulating layer 290 located on the upper part of the laminate where the contact layer 26 is located is removed (patterned) by photolithography and wet etching, and a second electrode 28 (p-electrode) is deposited by photolithography and vapor deposition, completing the excitation light source 200A side.

[0235] Next, the manufacture of the resonator portion (optical device) will be described. As shown in Fig. 56(d), a SiN layer 140a to be the second light confinement layer 140 is laminated by plasma CVD on one surface of a light-transmitting substrate 15 (for example, a quartz plate). Furthermore, as shown in Fig. 57(a), a plurality of recesses are formed on the surface of the SiN layer 140a by electron beam lithography and dry etching to define a plurality of modified refractive index areas 120b of the PC layer 120. At this time, the surface area of ​​the SiN layer 140a in which the plurality of recesses are formed becomes the basic layer 120a, and these plurality of recesses become a plurality of modified refractive index areas 120b.

[0236] Next, a TiO2 layer 120c is formed on the surface of the SiN layer 140a (the surface of the base layer 120a) and on the inner walls and bottoms of the multiple recesses (multiple modified refractive index areas 120b) by atomic layer deposition (ALD), thereby obtaining the second optical confinement layer 140 as shown in Figure 57(b).

[0237] On the other hand, on the excitation light source side (FIG. 56(c)), as shown in FIG. 57(c), a partition member 111 made of ultraviolet curing resin is formed on the first optical confinement layer 130 to define a space to become the UC layer 11. The partition member 111 is formed by patterning the ultraviolet curing resin (the same as the constituent material of the UC layer 11) applied on the first optical confinement layer 130. Furthermore, on the first optical confinement layer 130, as shown in FIG. 57(d), a spacer 110 is arranged along the edge of the GaAs substrate 21. Specifically, an ultraviolet curing resin in which beads for the spacer 110 are dispersed is applied on the first optical confinement layer 130. At this stage, the resin injection opening 112 (an opening into which a resin containing an upconversion material is injected) is left open. In this way, by applying the spacer 110, parallelism can be ensured over a wide range (wafer size).

[0238] Then, as shown in Fig. 58(a), the excitation light source side shown in Fig. 57(d) and the optical device side shown in Fig. 57(b) are combined and placed in a vacuum. In this state, the space in which the UC layer 11 is to be formed is surrounded by a spacer 110 (an ultraviolet curing resin layer containing a plurality of beads) (a resin injection opening 112 is provided) as shown in Fig. 58(b), and a partition member 111 is disposed inside the spacer 110.

[0239] Then, as shown in FIG. 58(c), ultraviolet curable resin (containing the same upconversion material as the partition member 111) is injected from the resin injection opening 112 into the space secured by the spacer 110. After that, ultraviolet rays are irradiated from the substrate 15 side to harden the injected ultraviolet curable resin. FIG. 58(d) is a plan view showing the state of the UC layer 11 after UV curing. Then, the product shown in FIG. 58(c) is cut by a dicing method at the element separation positions indicated by the cutting lines Sa and Sb to obtain a light emitting device having the cross-sectional structure shown in FIG. 46(a). [Explanation of symbols]

[0240] 1A to 1H, 1J... Light emitting device, 10A to 10E, 10A1, 100A to 100F... Optical device, 11... UC layer (upconversion layer), 12A, 120... PC layer (photonic crystal layer), 12a, 120a... Basic layer, 11b, 12b, 12c, 120b... Modified refractive index area, 120c... TiO2 layer, 12B, 12C... Phase modulation layer, 13... First light reflecting layer (first light confinement layer), 13a...surface, 14...second light reflecting layer (second light confinement layer), 110...spacer, 111...partition member, 112...opening for resin injection, 130...first light confinement layer, 140...second confinement layer, 141...base, 142...cover layer, 15...substrate, 16...dichroic mirror, 17...diffractive optical element, 20A, 20B, 20C, 200A...excitation light source, 21...semiconductor substrate, 21a...main surface , 21b... rear surface, 22... active layer, 23... PC layer, 23a... base layer, 23b... modified refractive index area, 24... first cladding layer, 25... second cladding layer, 26... contact layer, 27... first electrode (n electrode), 27a... opening, 28... second electrode (p electrode), 29... first DBR layer, 30... second DBR layer, 31... first electrode, 33... slit, 40... spatial light modulator, 41... lens, 42, 201, 202... excitation Light source, 290...Insulating layer, 500...Submount, 510...P electrode pad, 520...N electrode pad, E1...1st light image area, E2...2nd light image area, E3...0th order light, D...straight line, G...center of gravity, Lex ,Lex1,Lex2...excitation light, Lout...light, Lout1...laser light, Lout2...light image, O...lattice point, Q...center, R...unit region, RIN...inner region, ROUT...outer region, θ...tilt angle.

Claims

1. an upconversion layer including an upconversion material that receives excitation light in a first wavelength range and outputs light in a second wavelength range that is shorter than the first wavelength range; a first light reflecting layer having a light reflecting property of reflecting at least a part of light in the second wavelength range; a second light reflecting layer having a light reflecting property of reflecting a part of the light in the second wavelength range while transmitting the remainder, the second light reflecting layer being disposed such that the upconversion layer is located between the first light reflecting layer and the second light reflecting layer; a resonance mode forming layer provided between the upconversion layer and the first light reflecting layer or between the upconversion layer and the second light reflecting layer, the resonance mode forming layer including a base layer and a plurality of modified refractive index areas having a refractive index different from that of the base layer and two-dimensionally distributed on a reference plane perpendicular to a thickness direction of the resonance mode forming layer, and forming a resonance mode of light in the second wavelength range along the reference plane; An optical device comprising:

2. an upconversion layer including an upconversion material that receives excitation light in a first wavelength range and outputs light in a second wavelength range that is shorter than the first wavelength range; a first optical confinement layer having an optical reflectance characteristic of reflecting at least a part of the light in the second wavelength range; a second optical confinement layer having an optical reflectance characteristic of reflecting a part of the light in the second wavelength range while transmitting the remaining part, the second optical confinement layer being disposed such that the up-conversion layer is located between the first optical confinement layer and the second optical confinement layer; a resonance mode forming layer provided between the upconversion layer and the first optical confinement layer or between the upconversion layer and the second optical confinement layer, the resonance mode forming layer including a base layer and a plurality of modified refractive index areas having a refractive index different from that of the base layer and two-dimensionally distributed on a reference plane perpendicular to a thickness direction of the resonance mode forming layer, and forming a resonance mode of light in the second wavelength range along the reference plane; An optical device comprising:

3. each of the first optical confinement layer and the second optical confinement layer includes an optical reflection layer having a multi-layer stacked structure, or a single layer made of a single material having a substantially uniform refractive index distribution along a thickness direction from the first optical confinement layer to the second optical confinement layer and a refractive index lower than a refractive index of the up-conversion layer; 3. The optical device of claim 2.

4. the second optical confinement layer has a single-layer structure in which a part of the second optical confinement layer including a layer surface facing the upconversion layer constitutes the basic layer, and a plurality of recesses for defining the plurality of modified refractive index areas are provided on the layer surface.

3. The optical device of claim 2.

5. an upconversion layer including an upconversion material that receives excitation light in a first wavelength range and outputs light in a second wavelength range that is shorter than the first wavelength range; a first optical confinement layer having an optical reflectance characteristic of reflecting at least a part of the light in the second wavelength range; a second optical confinement layer having an optical reflection characteristic of reflecting a part of the light in the second wavelength range while transmitting the remaining part, the second optical confinement layer being disposed so that the up-conversion layer is located between the first optical confinement layer and the second optical confinement layer, and having a single-layer structure in which a resonance mode of the light in the second wavelength range is formed; a resonance mode forming layer that forms the resonance mode of light in the second wavelength range, the resonance mode forming layer being provided on a side where a layer surface of the second light confinement layer facing the upconversion layer is located, and including a basic layer that constitutes a part of the second light confinement layer, and a plurality of modified refractive index areas that are defined by a plurality of recesses that are two-dimensionally distributed on the layer surface of the second light confinement layer as a reference plane perpendicular to a thickness direction of the resonance mode forming layer, and that have a refractive index different from that of the basic layer; An optical device comprising:

6. the resonant mode forming layer is a photonic crystal layer in which the multiple modified refractive index areas are periodically arranged. The optical device according to any one of claims 1 to 5.

7. An optical device that outputs an optical image, in a virtual square lattice set on the reference plane on which the plurality of modified refractive index areas are to be formed, each of the plurality of modified refractive index areas is arranged such that a center of gravity of the each of the plurality of modified refractive index areas is spaced a predetermined distance from a corresponding one of the lattice points of the virtual square lattice, and a line segment connecting the center of gravity and the corresponding lattice point has a rotation angle corresponding to the optical image with respect to the virtual square lattice. The optical device according to any one of claims 1 to 6.

8. An optical device that outputs an optical image, in a virtual square lattice set on the reference plane on which the plurality of modified refractive index areas are to be formed, the center of gravity of each of the plurality of modified refractive index areas is located on a straight line that passes through a corresponding one of the lattice points of the virtual square lattice and is inclined with respect to the square lattice, and a distance between the center of gravity and the corresponding lattice point is set individually according to the optical image. The optical device according to any one of claims 1 to 6.

9. a diffractive optical element disposed on an opposite side of the upconversion layer with respect to the second optical confinement layer. The optical device according to any one of claims 2 to 5.

10. a spatial light modulator disposed on an opposite side of the upconversion layer relative to the second optical confinement layer; The optical device according to any one of claims 2 to 5.

11. a dichroic mirror disposed on an opposite side of the upconversion layer with respect to the second optical confinement layer, the dichroic mirror having a light transmittance in the second wavelength range greater than a light transmittance in the first wavelength range; The optical device according to any one of claims 2 to 5.

12. The first wavelength range is a near infrared range, and the second wavelength range is a visible range. The optical device according to any one of claims 1 to 11.

13. An optical device according to any one of claims 2 to 5; an excitation light source integrated with the optical device via the first optical confinement layer, the excitation light source providing the excitation light to the upconversion layer; A light emitting device comprising:

14. the pump light source includes a photonic crystal surface emitting laser disposed on an opposite side of the upconversion layer with respect to the first optical confinement layer; an optical transmittance of the first optical confinement layer in the first wavelength range is greater than an optical transmittance of the first optical confinement layer in the second wavelength range; 14. The light emitting device of claim 13.

15. an area of ​​the photonic crystal layer of the photonic crystal surface-emitting laser as viewed from a stacking direction of the photonic crystal surface-emitting laser is larger than an area of ​​the up-conversion layer as viewed from a stacking direction of the optical device; 15. The light emitting device of claim 14.

16. The photonic crystal surface emitting laser comprises: a semiconductor substrate having a main surface and a back surface; a semiconductor laminate provided on the main surface of the semiconductor substrate, the semiconductor laminate including an active layer and a photonic crystal layer; a first electrode made of metal provided on the back surface of the semiconductor substrate; A second electrode provided on the semiconductor laminate; having the first electrode has an opening for passing the excitation light; 16. The light emitting device of claim 15, wherein at least a portion of the first optical confinement layer is disposed within the opening in the first electrode.

17. the pumping light source is disposed on an opposite side of the upconversion layer with respect to the first optical confinement layer, and includes a plurality of photonic crystal surface-emitting lasers each having the same structure as the photonic crystal surface-emitting laser; the plurality of photonic crystal surface emitting lasers are arranged one-dimensionally or two-dimensionally along a surface of the first optical confinement layer; 15. The light emitting device of claim 14.

18. The photonic crystal surface emitting laser comprises: a semiconductor substrate having a main surface and a back surface; a semiconductor laminate provided on the main surface of the semiconductor substrate, the semiconductor laminate including an active layer and a photonic crystal layer; a first electrode made of a transparent conductive film provided on the back surface of the semiconductor substrate; A second electrode provided on the semiconductor laminate; having 18. The light-emitting device of claim 14 or 17, wherein the excitation light passes through the first electrode to reach the first light confinement layer.

19. an area of ​​the photonic crystal layer of the photonic crystal surface-emitting laser as viewed from a stacking direction of the photonic crystal surface-emitting laser is smaller than an area of ​​the up-conversion layer as viewed from a stacking direction of the optical device; 15. The light emitting device of claim 14.

20. The photonic crystal surface emitting laser comprises: a semiconductor substrate having a main surface and a back surface; a semiconductor laminate provided on the main surface of the semiconductor substrate, the semiconductor laminate including an active layer and a photonic crystal layer; a first electrode provided on an exposed region of the main surface of the semiconductor substrate without being covered by the semiconductor laminate; A second electrode provided on the semiconductor laminate; having the first optical confinement layer is disposed on the back surface of the semiconductor substrate; 20. The light emitting device of claim 19.

21. the pumping light source is disposed on an opposite side of the upconversion layer with respect to the first optical confinement layer, and includes a plurality of photonic crystal surface-emitting lasers each having the same structure as the photonic crystal surface-emitting laser; the plurality of photonic crystal surface emitting lasers are arranged one-dimensionally or two-dimensionally along a surface of the first optical confinement layer; 21. The light emitting device of claim 20.

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