Light-emitting element, light source device, display device, head-mounted display, and biometric information acquisition device

Abstract

To provide a low-power light-emitting element, a light source device, a display device, a head-mounted display, and a biological information acquisition device.SOLUTION: A light-emitting element includes a first reflecting mirror and an active layer, the first reflecting mirror includes a multilayer film reflecting mirror in which a first refractive index layer having a first refractive index and a second refractive index layer higher than the first refractive index are alternately laminated, and a first layer provided on a first surface of the multilayer film reflecting mirror opposite to the active layer, and the first surface has an output area from which light generated in the active layer is output, the first layer is provided in a region including the emission center in a plan view from a direction perpendicular to the first surface, a portion of the light generated in the active layer is absorbed, and the light generated in the active layer and transmitted through the first layer is emitted.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a light-emitting element, a light source device, a display device, a head-mounted display, and a biological information acquisition device. [Background technology]

[0002] A surface-emitting laser (VCSEL) with a vertically oriented resonator is known (Patent Document 1). Surface-emitting lasers have a small active layer volume, low threshold power, and low power consumption. The output power of the device is in the range of several hundred μW to several mW, and can be increased to high output by arraying. Taking advantage of the characteristics of low output and low power consumption, they are expected to be used as light sources for wearable devices, such as light sources for retinal scanning displays, and as biometric light sources for acquiring iris information by utilizing their low output power. [Overview of the project] [Problems that the invention aims to solve]

[0003] The maximum exposure limit for the retina is tens to hundreds of microwatts, depending on the wavelength. When VCSELs are used as light sources for retinal displays or biometric applications, the light output is further reduced to, for example, around 0.05 to 0.2 microwatts. Conventional VCSELs have a light output of several hundred microwatts to several milliwatts, and conventional VCSELs cannot be used as eye-safe light sources as they are. For example, in order to use a VCSEL as an eye-safe light source, it is desirable to reduce the light output by several orders of magnitude compared to conventional VCSELs.

[0004] There are several ways to reduce the optical output of a VCSEL.

[0005] The simplest method is to place a component such as an ND (Neutral Density) filter in the optical path to reduce the light output. However, with this method, there is a risk that light exceeding the exposure limit may enter the retina if the component fails, such as by being missing.

[0006] Another approach involves finely controlling the current when the output is weak near the threshold current of the VCSEL. While this method may allow for the output of extremely low-power light, controlling minute currents is difficult, making it challenging to ensure stable operation of the device.

[0007] Another method involves designing the element to increase the reflectivity of the light-extracting mirror to over 99.99%. Theoretically, this method can reduce the light output to around tens of microwatts. However, to further reduce the light output by one or two orders of magnitude, the reflectivity of the mirror must be increased even more, and achieving this level of reflectivity is extremely difficult.

[0008] The present invention aims to provide a low-power light-emitting element, a light source device, a display device, a head-mounted display, and a biological information acquisition device. [Means for solving the problem]

[0009] According to one aspect of the disclosed technology, the light-emitting element is A surface-emitting laser, First reflector and active layer resonators including and, The second reflector, The first reflector comprises a multilayer reflector in which a first refractive index layer having a first refractive index and a second refractive index layer having a higher refractive index are alternately stacked, and a first layer provided on the first surface of the multilayer reflector opposite to the active layer, the first surface having an emission region from which light generated in the active layer is emitted, and the first layer is provided in a region including the emission center in a plan view from a direction perpendicular to the first surface, and absorbs a portion of the light generated in the active layer. The light generated in the active layer and transmitted through the first layer is emitted, the resonator is provided between the first reflector and the second reflector, the emission region has, in a plan view from a direction perpendicular to the first surface, a first region including the emission center and a second region located around the first region, the first layer is provided in the first region, the reflectance of the portion of the first reflector that overlaps with the first region in the plan view, as seen from the active layer side, is higher than the reflectance of the portion of the first reflector that overlaps with the second region in the plan view, as seen from the active layer side, and the nodes of the longitudinal mode standing waves contained in the light generated in the active layer are located on the first surface of the multilayer reflector in the second region. ru. [Effects of the Invention]

[0010] According to the disclosed technology, a low-power light source can be provided. [Brief explanation of the drawing]

[0011] [Figure 1]It is a cross-sectional schematic diagram showing a surface-emitting laser according to the first embodiment. [Figure 2] It is a plan view showing an example of the first region and the metal layer. [Figure 3] It is a cross-sectional schematic diagram showing a surface-emitting laser according to the second embodiment. [Figure 4] It is a cross-sectional schematic diagram showing a surface-emitting laser according to the third embodiment. [Figure 5] It is a cross-sectional schematic diagram showing a surface-emitting laser according to the fourth embodiment. [Figure 6] It is a diagram showing the result of the first calculation example regarding the fourth embodiment. [Figure 7] It is a diagram showing the result of the second calculation example regarding the fourth embodiment. [Figure 8] It is a diagram showing the result of the third calculation example regarding the fourth embodiment. [Figure 9] It is a cross-sectional schematic diagram showing a surface-emitting laser according to the first modification of the fourth embodiment. [Figure 10] It is a cross-sectional schematic diagram showing a surface-emitting laser according to the second modification of the fourth embodiment. [Figure 11] It is a cross-sectional schematic diagram showing a surface-emitting laser according to the third modification of the fourth embodiment. [Figure 12] It is a cross-sectional schematic diagram showing a surface-emitting laser according to the fifth embodiment. [Figure 13] It is a diagram showing the result of the fourth calculation example regarding the fifth embodiment. [Figure 14] [[ID=F39]]It is a cross-sectional schematic diagram showing a surface-emitting laser according to a modification of the fifth embodiment. [Figure 15] It is a cross-sectional schematic diagram showing a surface-emitting laser according to the sixth embodiment. [Figure 16] It is a diagram showing the result of the fifth calculation example regarding the sixth embodiment. [Figure 17] It is a cross-sectional schematic diagram showing a surface-emitting laser according to a modification of the sixth embodiment. [Figure 18] It is a cross-sectional schematic diagram showing a surface-emitting laser according to the seventh embodiment. [Figure 19] It is a diagram showing the result of the sixth calculation example regarding the seventh embodiment. [Figure 20] This figure shows an example of the configuration of a projection device according to the eighth embodiment. [Figure 21] This is a perspective view of an example configuration of an HMD according to the 9th embodiment. [Figure 22] This is a cross-sectional view of an example configuration of an HMD according to the ninth embodiment. [Figure 23] This figure shows an example configuration of a biometric authentication device according to the 10th embodiment. [Modes for carrying out the invention]

[0012] Embodiments of this disclosure will be described below with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant descriptions will be omitted as appropriate.

[0013] Furthermore, the embodiments described below illustrate examples of light-emitting elements that embody the technical concept of the present invention, including a surface-emitting laser, a light source device, a display device, a head-mounted display, and a biological information acquisition device, and the present invention is not limited to the embodiments described below.

[0014] (First Embodiment) First, the first embodiment will be described. The first embodiment relates to a surface-emitting laser. Figure 1 is a schematic cross-sectional view showing a surface-emitting laser according to the first embodiment.

[0015] As shown in Figure 1, the surface-emitting laser 1 according to the first embodiment includes a substrate 101, a lower reflector 102 (second reflector), a lower spacer layer 103, an active layer 104, an upper spacer layer 105, and an upper reflector 108 (first reflector). The upper reflector 108 includes a multilayer reflector 107 and a metal layer 109. The metal layer 109 is an example of a first layer. The lower reflector 102 is provided on the substrate 101, the lower spacer layer 103 is provided on the lower reflector 102, and the active layer 104 is provided on the lower spacer layer 103. The upper spacer layer 105 is provided on the active layer 104, the multilayer reflector 107 is provided on the upper spacer layer 105, and the metal layer 109 is provided on the multilayer reflector 107. The multilayer reflecting mirror 107 has a low refractive index layer 107A and a high refractive index layer 107B, with the low refractive index layer 107A and the high refractive index layer 107B being alternately stacked. The low refractive index layer 107A has a first refractive index, and the high refractive index layer 107B has a second refractive index that is higher than the first refractive index. The resonator 106 is composed of a lower spacer layer 103, an active layer 104, and an upper spacer layer 105. The metal layer 109 is provided on the exit surface 110 of the multilayer reflecting mirror 107 opposite to the resonator 106.

[0016] The upper spacer layer 105 includes a current-constricting layer 123. The current-constricting layer 123 includes a conductive region 121 and an insulating region 122. The conductive region 121 is surrounded by the insulating region 122. The current-constricting layer 123 limits the region in the active layer 104 where current flows. When carriers are injected into the active layer 104, a standing wave 132 of light is generated perpendicular to the substrate surface (main surface) of the substrate 101 at a wavelength defined by the resonator 106. The conductive region 121 has a circular planar shape, for example, when viewed from a direction perpendicular to the emission surface 110 of the multilayer reflector 107. In the first embodiment, the center of the region overlapping with the conductive region 121 of the active layer 104 in a plan view is defined as the emission center 120, and light is emitted towards the multilayer reflector 107.

[0017] Figure 1 schematically shows the positions of the antinodes and nodes of the standing wave 132. If the wavelength of the standing wave 132 defined by the resonator 106 is λ, then the total film thickness of the low refractive index layer 107A and the high refractive index layer 107B for one period (one pair) corresponds to an optical thickness of λ / 2. For example, the optical thickness of each of the low refractive index layer 107A and the high refractive index layer 107B is λ / 4. In the first embodiment, the nodes of the standing wave 132 are located on the exit surface 110 of the multilayer reflecting mirror 107. For example, the low refractive index layer 107A with an optical thickness of λ / 4 constitutes the exit surface 110. That is, in the direction of light emission, the multilayer reflecting mirror 107 is terminated by the low refractive index layer 107A. For example, the multilayer reflecting mirror 107 contains N high refractive index layers 107B and N+1 low refractive index layers 107A (where N is a natural number).

[0018] The emission surface 110 of the multilayer reflecting mirror 107 has an emission region 113 from which light generated in the active layer 104 is emitted. The emission region 113 also has a first region 111 that includes the emission center 120 in a plan view, and a second region 112 located around the first region 111. The second region 112 surrounds the first region 111, for example. For example, the first region 111 is a circular region, and the second region 112 is an annular region. The first region 111 is a region with high light intensity (electric field intensity) of the lateral fundamental mode 131 that includes the emission center 120.

[0019] The metal layer 109 is provided in the first region 111 and absorbs a portion of the light generated in the active layer 104. The material of the metal layer 109 is not limited; for example, any material that can absorb light with a desired film thickness can be used. The material of the metal layer 109 may be a metal with high reflectivity across the entire visible range, such as Al and Ag, or a metal with low reflectivity, such as Cr. By having the metal layer 109 in the upper reflector 108, the output of the surface-emitting laser 1 can be set to 0.01 μW or more and less than 100 μW, more preferably 0.01 μW or more and less than 50 μW, and even more preferably 0.01 μW or more and less than 1 μW.

[0020] Incidentally, single-mode operation is preferable for controlling and creating an image by scanning light. In the first embodiment, the reflectance of the portion of the upper reflector 108 that overlaps with the first region 111 in a plan view, as seen from the active layer 104 side, is higher than the reflectance of the portion of the upper reflector 108 that overlaps with the second region 112 in a plan view, as seen from the active layer 104 side. As a result, the oscillation threshold of higher-order modes becomes higher than the oscillation threshold of single-mode in the in-plane transverse direction, and the surface-emitting laser 1 operates in single mode. In addition, since the metal layer 109 absorbs a portion of the light, the optical output of the surface-emitting laser 1 can be suppressed. For example, the optical output of the surface-emitting laser 1 can be set to approximately sub-μW to several tens of μW, which is suitable for eye safety. In other words, according to the first embodiment, both eye safety through low output and single-mode operation can be achieved.

[0021] Note that the planar shapes of the first region 111 and the metal layer 109 do not have to be circular. Figure 2 is a plan view showing an example of the first region 111 and the metal layer 109. As shown in the example in Figure 2, the planar shapes of the first region 111 and the metal layer 109 may be elliptical. In this way, the polarization can be controlled by having anisotropy in two directions that are mutually orthogonal in the in-plane direction of the planar shapes of the first region 111 and the metal layer 109. The planar shapes of the first region 111 and the metal layer 109 may be rectangular, or they may be more complex shapes. The metal layer 109 functions as a higher-order mode filter with such in-plane anisotropy. By providing the metal layer 109 that functions as a higher-order mode filter, the area of ​​the first region 111 can be increased compared to when there is no higher-order mode filter, and the resistance of the element can be reduced. The same applies to the following embodiments and modifications.

[0022] It is sufficient that there are nodes of the standing wave 132 on the emission surface 110 of the multilayer reflector 107, and it is not necessary for the multilayer reflector 107 to be terminated with a low refractive index layer 107A in the direction of light emission. For example, the multilayer reflector 107 may be terminated with a high refractive index layer having an optical thickness of λ / 2.

[0023] The current-constricting layer 123 may be provided within the multilayer reflector 107 instead of within the upper spacer layer 105. The same applies to subsequent embodiments and modifications.

[0024] There may be a metal layer thinner than the metal layer 109 surrounding the metal layer 109.

[0025] (Second Embodiment) Next, a second embodiment will be described. The second embodiment differs from the first embodiment mainly in the configuration of the upper reflector. Figure 3 is a schematic cross-sectional view showing a surface-emitting laser according to the second embodiment.

[0026] As shown in Figure 3, the surface-emitting laser 2 according to the second embodiment has an upper reflector 208 (first reflector) instead of the upper reflector 108. The upper reflector 208 has a multilayer reflector 207, a metal layer 209a, and a metal layer 209b. The metal layer 209a is an example of a first layer, and the metal layer 209b is an example of a second layer. The multilayer reflector 207 is provided on the upper spacer layer 105, and the metal layers 209a and 209b are provided on the multilayer reflector 207. The metal layers 209a and 209b are provided on the emission surface 210 of the multilayer reflector 207 opposite to the resonator 106.

[0027] Figure 3 schematically shows the positions of the antinodes and nodes of the standing wave 132. In the second embodiment, the antinodes of the standing wave 132 are located on the exit surface 210 of the multilayer mirror 207. For example, a high refractive index layer 107B with an optical thickness of λ / 4 constitutes the exit surface 210. That is, in the direction of light emission, the multilayer mirror 207 is terminated by the high refractive index layer 107B. For example, the multilayer mirror 207 includes N high refractive index layers 107B and N low refractive index layers 107A.

[0028] The exit surface 210 of the multilayer reflecting mirror 207 has an exit region 113, similar to the first embodiment, and the exit region 113 has a first region 111 and a second region 112. The metal layer 209a is provided in the first region 111 and absorbs a portion of the light generated in the active layer 104. The metal layer 209b is provided in the second region 112 and absorbs a portion of the light generated in the active layer 104. The refractive index of the metal layer 209a is lower than that of the metal layer 209b. The materials of the metal layers 209a and 209b are not limited as long as the refractive index of the metal layer 209a is lower than that of the metal layer 209b. The metal layer 209b may also be provided outside the exit region 113 in a plan view.

[0029] The other configurations are the same as in the first embodiment.

[0030] In the second embodiment, the reflectance of the portion of the upper reflector 208 that overlaps with the first region 111 in a plan view, as seen from the active layer 104 side, is higher than the reflectance of the portion of the upper reflector 208 that overlaps with the second region 112 in a plan view, as seen from the active layer 104 side. Therefore, similar to the first embodiment, the oscillation threshold of higher-order modes becomes higher than the oscillation threshold of single-mode in the in-plane transverse direction, and the surface-emitting laser 2 operates in single mode. In addition, since the metal layers 209a and 209b absorb a portion of the light, the optical output of the surface-emitting laser 2 can be suppressed. For example, the optical output of the surface-emitting laser 2 can be set to approximately sub-μW to several tens of μW, which is suitable for eye safety. In other words, both eye safety and single-mode operation can be achieved with the second embodiment as well.

[0031] Furthermore, if the reflectance of the portion of the upper reflector 208 that overlaps with the first region 111, as viewed from the active layer 104 side, is higher than the reflectance of the portion of the upper reflector 208 that overlaps with the second region 112, as viewed from the active layer 104 side, the materials of the metal layers 209a and 209b may be the same. For example, if metal layer 209a is thicker than metal layer 209b, the reflectance of the portion of the upper reflector 208 that overlaps with the first region 111, as viewed from the active layer 104 side, will be higher than the reflectance of the portion of the upper reflector 208 that overlaps with the second region 112, as viewed from the active layer 104 side. Also, if the difference in refractive index between metal layers 209a and 209b is small, the difference in reflectance can be increased if metal layer 209a is thicker than metal layer 209b. If the difference in refractive index between metal layers 209a and 209b is large, metal layer 209a may be thicker than metal layer 209b.

[0032] It is sufficient that there is an antinode of the standing wave 132 on the exit surface 210 of the multilayer reflecting mirror 207, and it is not necessary for the multilayer reflecting mirror 207 to be terminated with a high refractive index layer 107B in the direction of light emission. For example, the multilayer reflecting mirror 207 may be terminated with a low refractive index layer with an optical thickness of λ / 2.

[0033] (Third embodiment) Next, a third embodiment will be described. The third embodiment differs from the first embodiment and others mainly in the configuration of the upper reflector. Figure 4 is a schematic cross-sectional view showing a surface-emitting laser according to the third embodiment.

[0034] As shown in Figure 4, the surface-emitting laser 3 according to the third embodiment has an upper reflector 308 (first reflector) instead of the upper reflector 108. The upper reflector 308 has a multilayer reflector 307 and a metal layer 309. The multilayer reflector 307 is provided on the upper spacer layer 105, and the metal layer 309 is provided on the multilayer reflector 307. The metal layer 309 is provided on the emission surface 310 of the multilayer reflector 307 opposite to the resonator 106.

[0035] Figure 4 schematically shows the positions of the antinodes and nodes of the standing wave 132. The exit surface 310 of the multilayer reflector 307 has an exit region 113, similar to the first embodiment, and the exit region 113 has a first region 111 and a second region 112. In the third embodiment, on the exit surface 310 of the multilayer reflector 307, the nodes of the standing wave 132 are in the first region 111, and the antinodes of the standing wave 132 are in the second region 112. For example, in the first region 111, a low refractive index layer 107A with an optical thickness of λ / 4 constitutes the exit surface 310, and in the second region 112, a high refractive index layer 107B with an optical thickness of λ / 4 constitutes the exit surface 310. In other words, in the direction of light emission, the multilayer reflector 307 is terminated by the low refractive index layer 107A in the first region 111 and by the high refractive index layer 107B in the second region 112. For example, the multilayer reflecting mirror 307 includes N high refractive index layers 107B and N-1 low refractive index layers 107A in the portion overlapping with the first region 111, and includes N high refractive index layers 107B and N low refractive index layers 107A in the portion overlapping with the second region 112.

[0036] The metal layer 309 is provided in the first region 111 and the second region 112, and absorbs a portion of the light generated in the active layer 104. The metal layer 309 may also be provided outside the emission region 113 in a plan view.

[0037] In the third embodiment, the reflectance of the portion of the upper reflector 308 that overlaps with the first region 111 in a plan view, as seen from the active layer 104 side, is higher than the reflectance of the portion of the upper reflector 308 that overlaps with the second region 112 in a plan view, as seen from the active layer 104 side. As a result, the oscillation threshold for higher-order modes becomes higher than the oscillation threshold for single-mode in the in-plane transverse direction, and the surface-emitting laser 3 operates in single mode. In addition, since the metal layer 309 absorbs a portion of the light, the optical output of the surface-emitting laser 3 can be suppressed. For example, the optical output of the surface-emitting laser 3 can be set to approximately sub-μW to several tens of μW, which is suitable for eye safety. In other words, according to the third embodiment, both eye safety and single-mode operation can be achieved.

[0038] Furthermore, the multilayer mirror 307 may include N high-refractive-index layers 107B and N+1 low-refractive-index layers 107A in the portion overlapping with the first region 111, and N high-refractive-index layers 107B and N low-refractive-index layers 107A in the portion overlapping with the second region 112. In this configuration as well, at the exit surface 310 of the multilayer mirror 307, there are nodes of the standing wave 132 in the first region 111 and antinodes of the standing wave 132 in the second region 112.

[0039] (Fourth Embodiment) Next, a fourth embodiment will be described. The fourth embodiment relates to a surface-emitting laser. Figure 5 is a schematic cross-sectional view showing a surface-emitting laser according to the fourth embodiment. The fourth embodiment corresponds to a specific example of the first embodiment.

[0040] The surface-emitting laser 4 according to the fourth embodiment is a surface-emitting laser with a wavelength λ of 445 nm using GaN. As shown in Figure 5, the surface-emitting laser 4 includes a substrate 401, a lower reflector 402 (second reflector), a lower spacer layer 403, an active layer 404, an upper spacer layer 405, and an upper reflector 408 (first reflector). The upper reflector 408 includes a multilayer reflector 407 and a metal layer 409. The surface-emitting laser 4 further includes a current-constricting layer 423, a transparent conductive layer 443, a lower electrode 441, and an upper electrode 442. The lower reflector 402 is provided on the substrate 401, the lower spacer layer 403 is provided on the lower reflector 402, and the active layer 404 is provided on the lower spacer layer 403. An upper spacer layer 405 is provided on the active layer 404, a current-constricting layer 423 is provided on the upper spacer layer 405, and a transparent conductive layer 443 is provided on the current-constricting layer 423. A multilayer reflector 407 is provided on the transparent conductive layer 443, and a metal layer 409 is provided on the multilayer reflector 407. The resonator 406 is formed from the lower spacer layer 403, the active layer 404, and the upper spacer layer 405. The metal layer 409 is provided on the exit surface 410 of the multilayer reflector 407 opposite to the resonator 406.

[0041] The substrate 401 is, for example, a GaN substrate.

[0042] The lower reflector 402 is a multilayer reflector composed of a semiconductor including, for example, a 45-period high-refractive-index layer and a low-refractive-index layer. For example, the high-refractive-index layer is an InGaN layer, and the low-refractive-index layer is a superlattice layer composed of multiple AlGaN layers and GaN layers. The optical thickness of one period of the high-refractive-index layer and the low-refractive-index layer is λ / 2.

[0043] The multilayer reflector 407 has a similar configuration to the multilayer reflector 107. That is, the multilayer reflector 407 has low refractive index layers and high refractive index layers, which are alternately stacked. The low refractive index layers have a first refractive index, and the high refractive index layers have a second refractive index higher than the first refractive index. The multilayer reflector 407 is a multilayer reflector composed of a dielectric including, for example, 8.5 periods of high refractive index layers and low refractive index layers. For example, the high refractive index layers are Ta2O5 layers, and the low refractive index layers are SiO2 layers. The optical thickness of one period of high refractive index layers and low refractive index layers is λ / 2. For example, the multilayer reflector 407 includes 8 Ta2O5 layers and 9 SiO2 layers.

[0044] The active layer 404 has a multiple quantum well structure containing multiple InGaN layers and GaN layers. The lower spacer layer 403 is an n-type GaN layer, and the upper spacer layer 405 is a p-type GaN layer. The upper spacer layer 405, the active layer 404, and a portion of the lower spacer layer 403 are etched to form a mesa structure.

[0045] The current-constricting layer 423 includes a conductive region 421 and an insulating region 422. The conductive region 421 is surrounded by the insulating region 422. For example, the conductive region 421 is part of the upper spacer layer 405 and is composed of p-type GaN, and the insulating region 422 is an SiO2 layer. The current-constricting layer 423 limits the region in the active layer 404 where current flows. When carriers are injected into the active layer 404, a standing wave of light 432 is generated perpendicular to the substrate surface (main surface) of the substrate 401 at a wavelength λ (445 nm) defined by the resonator 406. In the fourth embodiment, the light is emitted towards the multilayer reflector 407, with the center of the region overlapping with the conductive region 421 of the active layer 404 in a plan view being the emission center 420.

[0046] Figure 5 schematically shows the positions of the antinodes and nodes of the standing wave 432. In the fourth embodiment, the resonator 406 is constructed with a thickness such that the standing wave 432 is generated at a wavelength λ of 445 nm. To obtain a high gain, the active layer 404 is located at the antinodes of the standing wave 432 where the light intensity is strong. To suppress light absorption, the transparent conductive layer 443 is located at the nodes of the standing wave 432. In addition, the nodes of the standing wave 432 are located on the exit surface 410 of the multilayer mirror 407. For example, a low refractive index layer with an optical thickness of λ / 4 constitutes the exit surface 410. In other words, in the direction of light emission, the multilayer mirror 407 is terminated by a low refractive index layer (SiO2 layer).

[0047] The emission surface 410 of the multilayer reflecting mirror 407 has an emission region 413 from which light generated in the active layer 404 is emitted. The emission region 413 has a first region 411 that includes the emission center 420 in a plan view, and a second region 412 located around the first region 411. The second region 412 surrounds the first region 411, for example. For example, the first region 411 is a circular region, and the second region 412 is an annular region. The first region 411 is a region with high light intensity of the lateral fundamental mode 431 that includes the emission center 420.

[0048] The metal layer 409 is provided in the first region 411 and absorbs a portion of the light generated in the active layer 404. The metal layer 409 is, for example, a Cr layer. The thickness of the metal layer 409 is, for example, 20 nm.

[0049] The material of the transparent conductive layer 443 is, for example, indium tin oxide (ITO). The lower electrode 441 is provided on the lower spacer layer 403 around the mesa structure. The lower electrode 441 has a Ti layer formed on the lower spacer layer 403 and an Al layer on top of this Ti layer. The upper electrode 442 has a Ti layer formed on the transparent conductive layer 443 and an Au layer on top of this Ti layer. When a voltage is applied between the lower electrode 441 and the upper electrode 442, a current flows through the active layer 404.

[0050] In the fourth embodiment, the reflectance of the portion of the upper reflector 408 that overlaps with the first region 411 in a plan view, as seen from the active layer 404 side, is higher than the reflectance of the portion of the upper reflector 408 that overlaps with the second region 412 in a plan view, as seen from the active layer 404 side. For example, the reflectance of the portion of the upper reflector 408 that overlaps with the first region 411 in a plan view, as seen from the active layer 404 side, is 0.9991, and the reflectance of the portion of the upper reflector 408 that overlaps with the second region 412 in a plan view, as seen from the active layer 404 side, is 0.9954. As a result, the oscillation threshold for higher-order modes becomes higher than the oscillation threshold for single-mode in the in-plane transverse direction, and the surface-emitting laser 4 operates in single-mode. In addition, because the metal layer 409 absorbs a portion of the light, the optical output of the surface-emitting laser 4 can be suppressed. For example, the optical output of the surface-emitting laser 4 can be set to a range of sub-μW to several tens of μW, which is suitable for eye safety. In other words, according to the fourth embodiment, it is possible to achieve both eye-safe operation and single-mode operation.

[0051] Next, a method for manufacturing the surface-emitting laser 4 according to the fourth embodiment will be described.

[0052] First, a lower reflector 402, a lower spacer layer 403, an active layer 404, and an upper spacer layer 405 are formed on the substrate 401 using a metal-organic chemical vapor deposition (MOCVD) apparatus. Next, impurities contained in the upper spacer layer 405 are activated by heat treatment. For example, the substrate 401 is heated during the heat treatment.

[0053] Next, using photolithography and dry etching, a mesa structure is formed in the upper spacer layer 405, the active layer 404, and a portion of the lower spacer layer 403 such that a portion of the lower spacer layer 403 remains in the thickness direction.

[0054] Next, the periphery of the upper spacer layer 405 is removed to a depth of approximately 20 nm using photolithography and dry etching. Then, an SiO2 layer is formed as an insulating region 422 by self-alignment using the mask used in dry etching. The SiO2 layer can be formed, for example, by electron beam (EB) deposition. In this way, the current constriction layer 423 is formed.

[0055] Next, a transparent conductive layer 443 is formed on the current-constricting layer 423, a lower electrode 441 is formed on the lower spacer layer 403, and an upper electrode 442 is formed on the insulating region 422 and the transparent conductive layer 443.

[0056] Next, a multilayer reflecting mirror 407 is formed on the transparent conductive layer 443. In forming the multilayer reflecting mirror 407, in order to position the transparent conductive layer 443 at the nodes of the standing wave 432, first a Ta2O5 layer for phase adjustment is formed, and then SiO2 layers and Ta2O5 layers are stacked alternately for 8.5 periods with an optical thickness of λ / 4. In the direction of light emission, by terminating the multilayer reflecting mirror 407 with an SiO2 layer (low refractive index layer) with an optical thickness of λ / 4, the nodes of the standing wave 432 are positioned on the emission surface 410.

[0057] Next, a metal layer 409 is formed in the region with high light intensity of the lateral fundamental mode 431, i.e., the first region 411.

[0058] In this way, the surface-emitting laser 4 according to the fourth embodiment can be manufactured.

[0059] In this disclosure, assuming that the thickness of the first layer is 0 nm, that is, that there is air on the multilayer mirror, the reflectance when light generated in the active layer is incident on the interface between the multilayer mirror and the air from the multilayer mirror side is defined as R0, and the reflectance when light generated in the active layer is incident on the interface between the multilayer mirror and the first layer from the multilayer mirror side is defined as R1, and R1 / R0 is called the reflectance ratio.

[0060] Furthermore, assuming that the thickness of the first layer is 0 nm, that is, that there is air on the multilayer reflecting mirror, the transmittance when light generated in the active layer is transmitted from the multilayer reflecting mirror to the air is defined as I0, and the transmittance when light generated in the active layer is transmitted from the multilayer reflecting mirror, on which the first metal layer is formed on the first surface, to the air is defined as I1, and I1 / I0 is called the transmittance ratio.

[0061] [First calculation example] Next, a calculation example (first calculation example) performed with respect to the fourth embodiment will be described. In the first calculation example, a laminate consisting of the lower reflector 402, resonator 406, multilayer reflector 407, and metal layer 509 of the fourth embodiment was used as a model. Furthermore, each layer was assumed to be formed as a solid. The multilayer reflector 407 is a dielectric multilayer reflector with a period of 8.5, and the exit surface 410 is terminated with a low refractive index layer, which is a node of the standing wave 432. The reflectance and transmittance of the upper reflector 408 as seen from the active layer 404 were calculated when the thickness of the Cr layer, which is the metal layer 409, was changed. The results are shown in Figure 6. Figure 6(a) shows the relationship between the thickness of the Cr layer and the reflectance and transmittance of the upper reflector 408. Figure 6(b) shows the relationship between the thickness of the Cr layer and the transmittance ratio of the upper reflector 408, which is derived from Figure 6(a).

[0062] Here, the refractive index of Ta2O5 was set to 2.21, the refractive index of SiO2 to 1.46, and the complex refractive index of Cr to 2.27 + 3.10i for the calculations. As shown in Figure 6, the reflectance increases as the thickness of the Cr layer increases, and becomes almost constant once a certain thickness is reached. Conversely, the transmittance and transmittance ratio decrease as the thickness of the Cr layer increases, and become almost constant once a certain thickness is reached. In the case of a Cr layer with a thickness of 20 nm, the reflectance ratio was 1.00368 and the transmittance ratio was 0.0326. Thus, by using a Cr layer, the reflectance of the upper reflector can be increased, and the light output can be weakened by the absorption of the Cr layer. Since the reflectance increases with thickness of the Cr layer, a reflectance distribution can be provided even if a thinner Cr layer is formed in the second region 412 than in the first region 411. For example, the thickness of the Cr layer in the first region 111 can be set to 20-40 nm, which is sufficient to weaken the light output, and a Cr layer with a thickness of about 1-5 nm may be formed in the second region 112. In this case, a reflectivity distribution is provided within the plane, allowing the surface-emitting laser 4 to operate in single mode, and the optical output can be weakened even in the second region 112. Such a surface-emitting laser 4 can improve the unimodality of the far-field image.

[0063] [Second calculation example] Next, we will describe another calculation example (second calculation example) performed with respect to the fourth embodiment. In the second calculation example, using the same model as in the first calculation example, we calculated the reflectance of the upper mirror 408 as seen from the active layer 404 when the optical thickness of the low refractive index layer (SiO2 layer) on the outermost layer of the multilayer mirror 407 was reduced from λ / 4. The results are shown in Figure 7. The period in the legend in Figure 7 is the period of the multilayer mirror 407.

[0064] In the fourth embodiment, the second region 112 corresponds to point A in Figure 7, where the thickness of the Cr layer is 0 nm at period 8.5. Even when the optical thickness of the outermost layer (SiO2 layer) of the first region 111 is reduced from λ / 4 (=0.25λ) to λ / 4-0.20λ, the reflectivity decreases only slightly (range B in the figure), and is higher than that of point A. It is most preferable that the outermost layer of the multilayer mirror 407 is a low refractive index layer with an optical thickness of λ / 4, in other words, that the standing wave is nodal at the exit surface 410. However, Figure 7 shows that even when the optical thickness of the outermost layer of the multilayer mirror 407 in the first region 111 is reduced from λ / 4 to about λ / 4-0.20λ, both eye-safe and single-mode operation can be achieved.

[0065] [Third calculation example] Next, we will describe another calculation example (third calculation example) performed with respect to the fourth embodiment. In the third calculation example, using the same model as in the first calculation example, we calculated the reflectance of the upper mirror 408 as seen from the active layer 404 when the optical thickness of the low refractive index layer (SiO2 layer) on the outermost layer of the multilayer mirror 407 was increased from λ / 4. The results are shown in Figure 8. The period in the legend in Figure 8 is the period of the multilayer mirror 407.

[0066] In the fourth embodiment, the second region 112 corresponds to point A in Figure 8, where the thickness of the Cr layer is 0 nm at period 8.5. Even when the optical thickness of the outermost layer (SiO2 layer) of the first region 111 is increased from λ / 4 (=0.25λ) to λ / 4 + 0.140λ, the reflectivity only decreases slightly (range C in the figure), and is higher than that of point A. It is most preferable that the outermost layer of the multilayer mirror 407 is a low refractive index layer with an optical thickness of λ / 4, in other words, that the standing wave is nodal at the exit surface 410. However, Figure 8 shows that even when the optical thickness of the outermost layer of the multilayer mirror 407 in the first region 111 is increased from λ / 4 to about λ / 4 + 0.140λ, both eye-safe and single-mode operation can be achieved.

[0067] (First modified example of the fourth embodiment) Next, a first modification of the fourth embodiment will be described. The first modification differs from the fourth embodiment mainly in the configuration of the metal layer. Figure 9 is a schematic cross-sectional view showing a surface-emitting laser according to the first modification of the fourth embodiment.

[0068] As shown in Figure 9, in the surface-emitting laser 4A according to the first modification of the fourth embodiment, the upper reflector 408 has a metal layer 409b in addition to the multilayer reflector 407 and the metal layer 409. The metal layer 409b is provided in the second region 412 and absorbs a portion of the light generated in the active layer 404. The metal layer 409b is made of the same type of metal as the metal layer 409, for example, a Cr layer. The metal layer 409b is thinner than the metal layer 409.

[0069] The other configurations are the same as in the fourth embodiment.

[0070] The same effects as in the fourth embodiment can be obtained with the first modification. Furthermore, as explained in the first calculation example, since the optical output can be weakened in the second region 112 while operating the surface-emitting laser 4A in single mode, the unimodality of the far-field image can be improved.

[0071] (Second modified example of the fourth embodiment) Next, a second modification of the fourth embodiment will be described. The second modification differs from the fourth embodiment mainly in the configuration of the multilayer mirror. Figure 10 is a schematic cross-sectional view showing a surface-emitting laser according to the second modification of the fourth embodiment.

[0072] As shown in Figure 10, in the surface-emitting laser 4B according to the second modification of the fourth embodiment, the upper reflector 408 has a multilayer reflector 407B instead of the multilayer reflector 407. In the multilayer reflector 407B, in the portion that overlaps with the first region 411 in a plan view, the outermost low refractive index layer (SiO2 layer) is thinner than the thickness in the multilayer reflector 407. For example, the optical thickness of the outermost low refractive index layer (SiO2 layer) in the multilayer reflector 407 is λ / 4, while the optical thickness in the multilayer reflector 407B is λ / 4 - 0.20λ or more and less than λ / 4. Therefore, in the first region 411, the nodes of the standing wave 432 are offset from the emission surface 410B of the multilayer reflector 407.

[0073] The other configurations are the same as in the fourth embodiment.

[0074] As explained in the second calculation example, both eye-safe and single-mode operation can be achieved with the second modification.

[0075] (Third modification of the fourth embodiment) Next, a third modification of the fourth embodiment will be described. The third modification differs from the fourth embodiment mainly in the configuration of the multilayer mirror. Figure 11 is a schematic cross-sectional view showing a surface-emitting laser according to the third modification of the fourth embodiment.

[0076] As shown in Figure 11, in the surface-emitting laser 4C according to the third modification of the fourth embodiment, the upper reflector 408 has a multilayer reflector 407C instead of the multilayer reflector 407. In the multilayer reflector 407C, in the portion that overlaps with the first region 411 in a plan view, the outermost low refractive index layer (SiO2 layer) is thicker than the thickness in the multilayer reflector 407. For example, the optical thickness of the outermost low refractive index layer (SiO2 layer) in the multilayer reflector 407 is λ / 4, while the optical thickness in the multilayer reflector 407B is greater than λ / 4 and less than or equal to λ / 4 + 0.140λ. Therefore, in the first region 411, the nodes of the standing wave 432 are offset from the emission surface 410C of the multilayer reflector 407.

[0077] The other configurations are the same as in the fourth embodiment.

[0078] As explained in the third calculation example, eye-safe and single-mode operation can also be achieved with the third modified example.

[0079] (Fifth embodiment) Next, a fifth embodiment will be described. The fifth embodiment differs from the fourth embodiment mainly in the configuration of the upper reflector. Figure 12 is a schematic cross-sectional view showing a surface-emitting laser according to the fifth embodiment. The fifth embodiment corresponds to a specific example of the second embodiment.

[0080] The surface-emitting laser 5 according to the fifth embodiment is a surface-emitting laser with a wavelength λ of 515 nm using GaN. As shown in Figure 12, the surface-emitting laser 5 according to the fifth embodiment has an upper reflector 508 (first reflector) instead of the upper reflector 408. The upper reflector 508 has a multilayer reflector 507, a metal layer 509a, and a metal layer 509b. The multilayer reflector 507 is provided on the transparent conductive layer 443, and the metal layers 509a and 509b are provided on the multilayer reflector 507. The metal layers 509a and 509b are provided on the emission surface 510 of the multilayer reflector 507 opposite to the resonator 406.

[0081] The lower reflector 402 is a multilayer reflector composed of semiconductors, for example, a high refractive index layer and a low refractive index layer with 50 periods. For example, the high refractive index layer is a GaN layer and the low refractive index layer is an AlInN layer. The optical thickness of the high refractive index layer and the low refractive index layer with 1 period is λ / 2.

[0082] The multilayer reflector 507 has a similar configuration to the multilayer reflector 207. That is, the multilayer reflector 507 has low refractive index layers and high refractive index layers, which are alternately stacked. The low refractive index layers have a first refractive index, and the high refractive index layers have a second refractive index higher than the first refractive index. The multilayer reflector 507 is a multilayer reflector composed of a dielectric including, for example, eight periods of high refractive index layers and low refractive index layers. For example, the high refractive index layers are Ta2O5 layers, and the low refractive index layers are SiO2 layers. The optical thickness of one period of high refractive index layers and low refractive index layers is λ / 2. For example, the multilayer reflector 507 includes eight Ta2O5 layers and eight SiO2 layers.

[0083] Figure 12 schematically shows the positions of the antinodes and nodes of the standing wave 532. In the fifth embodiment, the resonator 406 is constructed with a thickness such that the standing wave 532 is generated at a wavelength λ of 515 nm. To obtain a high gain, the active layer 404 is located at the antinodes of the standing wave 532 where the light intensity is strong. To suppress light absorption, the transparent conductive layer 443 is located at the nodes of the standing wave 532. In addition, there are antinodes of the standing wave 532 on the exit surface 510 of the multilayer mirror 507. For example, a high refractive index layer with an optical thickness of λ / 4 constitutes the exit surface 510. In other words, in the direction of light emission, the multilayer mirror 507 is terminated with a high refractive index layer (Ta2O5 layer).

[0084] The exit surface 510 of the multilayer reflecting mirror 507 has an exit region 413, similar to the fourth embodiment, and the exit region 413 has a first region 411 and a second region 412. The metal layer 509a is provided in the first region 411 and absorbs a portion of the light generated in the active layer 404. The metal layer 509b is provided in the second region 412 and absorbs a portion of the light generated in the active layer 404. The refractive index of the metal layer 509a is lower than that of the metal layer 509b. For example, the metal layer 509a is an Al layer and the metal layer 509b is a Cr layer. The film thickness of the metal layers 509a and 509b is, for example, 30 nm. The metal layer 509b may also be provided outside the exit region 413 in a plan view.

[0085] The other configurations are the same as in the fourth embodiment.

[0086] In the fifth embodiment, the reflectance of the portion of the upper reflector 508 that overlaps with the first region 411 in a plan view, as seen from the active layer 404 side, is higher than the reflectance of the portion of the upper reflector 508 that overlaps with the second region 412 in a plan view, as seen from the active layer 404 side. For example, the reflectance of the portion of the upper reflector 508 that overlaps with the first region 411 in a plan view, as seen from the active layer 404 side, is 0.9980, and the reflectance of the portion of the upper reflector 408 that overlaps with the second region 412 in a plan view, as seen from the active layer 404 side, is 0.9926. Therefore, similar to the fourth embodiment, the oscillation threshold of higher-order modes becomes higher than the oscillation threshold of single-mode in the in-plane transverse direction, and the surface-emitting laser 5 operates in single-mode. In addition, because the metal layers 509a and 509b absorb a portion of the light, the optical output of the surface-emitting laser 5 can be suppressed. For example, the optical output of the surface-emitting laser 5 can be set to a range of sub-μW to several tens of μW, which is suitable for eye safety. In other words, the fifth embodiment also makes it possible to achieve both eye-safe operation and single-mode operation.

[0087] Next, a method for manufacturing the surface-emitting laser 5 according to the fifth embodiment will be described.

[0088] First, the process up to the formation of the lower electrode 441 and the upper electrode 442 is carried out in the same manner as in the fourth embodiment. Next, a multilayer reflecting mirror 507 is formed on the transparent conductive layer 443. In forming the multilayer reflecting mirror 507, in order to make the transparent conductive layer 443 a node of the standing wave 532, first a Ta2O5 layer for phase adjustment is formed, and then SiO2 layers and Ta2O5 layers are stacked alternately for 8 periods with an optical thickness of λ / 4. In the direction of light emission, by terminating the multilayer reflecting mirror 507 with a Ta2O5 layer (high refractive index layer) with an optical thickness of λ / 4, the antinode of the standing wave 532 is positioned on the emission surface 510.

[0089] Next, a metal layer 509a is formed in the region of strong light intensity in the lateral basic mode 431, i.e., the first region 411. Then, a metal layer 509b is formed around the metal layer 509a. In forming the metal layer 509b, for example, the metal layer 509a can be used as a photomask, and a resist can be formed by exposing the substrate 401 from the back surface, thereby forming the metal layer 509b by self-alignment.

[0090] In this way, the surface-emitting laser 5 according to the fifth embodiment can be manufactured.

[0091] Furthermore, an Al layer may be used as the metal layer 509a and a Cr layer as the metal layer 509b, with metal layer 509b being thicker than metal layer 509a. In this case, metal layer 509b may be formed in front of metal layer 509a, and metal layer 509a may be formed on the first region 411 and the second region 412. When metal layer 509b is formed thickly, light transmitted through the multilayer reflector 507 is absorbed by metal layer 509b and is less likely to be reflected back to the multilayer reflector 507. For this reason, even if metal layer 509a is formed above it, it does not affect the reflectivity.

[0092] [4th calculation example] Next, a calculation example (the fourth calculation example) performed with respect to the fifth embodiment will be described. In the fourth calculation example, a laminate consisting of the lower reflector 402, resonator 406, multilayer reflector 507, and metal layer 509a or 509b of the fifth embodiment was used as a model. Furthermore, each layer was assumed to be formed as a solid. The multilayer reflector 507 is an 8-period dielectric multilayer reflector, with the exit surface 510 terminated by a high refractive index layer, forming an antinode of the standing wave 532. The reflectance and transmittance of the upper reflector 508 as seen from the active layer 404 were calculated when the film thickness of the Al layer or Cr layer, which is the metal layer 509a or 509b, was changed. The results are shown in Figure 13. Figure 13(a) shows the relationship between the film thickness of the metal layer (Al layer or Cr layer) and the reflectance and transmittance of the upper reflector 508. Figure 13(b) shows the relationship between the thickness of the metal layer and the transmission ratio of the upper reflector 508, which can be derived from Figure 13(a).

[0093] Here, calculations were performed using a refractive index of 2.20 for Ta2O5, 1.45 for SiO2, a complex refractive index of 2.91 + 3.33i for Cr, and a complex refractive index of 0.826 + 6.28i for Al. As shown in Figure 13, as the thickness of the metal layer increases, the reflectivity initially decreases, then increases, and becomes almost constant. The amount by which the refractive index decreases and the value at which it becomes constant differ depending on the type of metal. Specifically, for Al, which has a low refractive index, the reflectivity is higher than that of Cr. In a typical dielectric or semiconductor multilayer mirror, the reflectivity decreases when a low refractive index layer is formed on a high refractive index layer with an optical thickness of λ / 4. In contrast, when a layer of a low refractive index metal such as Al is formed, the reflectivity hardly decreases, and when formed with a sufficient thickness, the reflectivity becomes high. For an Al layer with a thickness of 30 nm, the reflectance ratio was 1.00019 and the transmittance ratio was 0.0374.

[0094] Furthermore, focusing on the Cr layer, the reflectance of the Cr layer in the range of 10 nm to 30 nm is generally lower than the reflectance of the Cr layer in the range of 1 nm to less than 10 nm or 40 nm or more. Therefore, by using Cr layers with different thicknesses as the metal layers 509a and 509b, the reflectance of the portion overlapping the first region 411 in a plan view of the upper reflector 508, as seen from the active layer 404 side, can be made higher than the reflectance of the portion overlapping the second region 412 in a plan view of the upper reflector 508, as seen from the active layer 404 side.

[0095] (Modified version of the fifth embodiment) Next, a modified version of the fifth embodiment will be described. The modified version differs from the fifth embodiment mainly in the configuration of the metal layer. Figure 14 is a schematic cross-sectional view showing a surface-emitting laser according to a modified version of the fifth embodiment.

[0096] As shown in Figure 14, in the surface-emitting laser 5A according to a modified example of the fifth embodiment, the upper reflector 508 has a metal layer 509c instead of a metal layer 509a, and a metal layer 509d instead of a metal layer 509b. Both metal layers 509c and 509d are Cr layers. The thickness of metal layer 409c is 40 nm or more, and the thickness of metal layer 409d is about 10 nm to 30 nm.

[0097] The other configurations are the same as in the fifth embodiment.

[0098] As explained in the fourth calculation example, in the modified version of the fifth embodiment, the reflectance of the portion of the upper reflector 508 that overlaps with the first region 411 in a plan view, as seen from the active layer 404 side, is higher than the reflectance of the portion of the upper reflector 508 that overlaps with the second region 412 in a plan view, as seen from the active layer 404 side. Therefore, as in the fifth embodiment, both eye-safe and single-mode operation can be achieved.

[0099] Furthermore, the thickness of the metal layer 509c may be 1 nm or more and less than 10 nm. Also, although it is difficult to obtain a large difference in reflectivity as with the Cr layer, Al layers with different thicknesses may be used as the metal layers 509c and 509d.

[0100] (Sixth Embodiment) Next, the sixth embodiment will be described. The sixth embodiment differs from the fourth embodiment and others mainly in the configuration of the upper reflector. Figure 15 is a schematic cross-sectional view showing a surface-emitting laser according to the sixth embodiment. The sixth embodiment corresponds to a specific example of the third embodiment.

[0101] The surface-emitting laser 6 according to the sixth embodiment is a surface-emitting laser with a wavelength λ of 445 nm using GaN. As shown in Figure 15, the surface-emitting laser 6 according to the sixth embodiment has an upper reflector 608 (first reflector) instead of the upper reflector 408. The upper reflector 608 has a multilayer reflector 607 and a metal layer 609. The multilayer reflector 607 is provided on the transparent conductive layer 443, and the metal layer 609 is provided on the multilayer reflector 607. The metal layer 609 is provided on the emission surface 610 of the multilayer reflector 607 opposite to the resonator 406.

[0102] Figure 15 schematically shows the positions of the antinodes and nodes of the standing wave 432. The exit surface 610 of the multilayer reflector 607 has an exit region 413, similar to the fourth embodiment, and the exit region 413 has a first region 411 and a second region 412. In the sixth embodiment, on the exit surface 610 of the multilayer reflector 607, the nodes of the standing wave 432 are in the first region 411 and the antinodes of the standing wave 432 are in the second region 412. For example, in the first region 411, a low refractive index layer with an optical thickness of λ / 4 constitutes the exit surface 610, and in the second region 412, a high refractive index layer with an optical thickness of λ / 4 constitutes the exit surface 610. In other words, in the direction of light emission, the multilayer reflector 607 is terminated by the low refractive index layer in the first region 411 and by the high refractive index layer in the second region 412. For example, the high refractive index layer is a Ta2O5 layer, and the low refractive index layer is an SiO2 layer. The optical thickness of the high refractive index and low refractive index layers for one period is λ / 2. For example, the multilayer mirror 607 includes 11 high refractive index layers and 10 low refractive index layers in the portion overlapping the first region 411, and includes 11 high refractive index layers and 11 low refractive index layers in the portion overlapping the second region 412. In other words, the multilayer mirror 607 is composed of a dielectric including 10.5 period high refractive index and low refractive index layers in the portion overlapping the first region 411, and is composed of a dielectric including 11 period high refractive index and low refractive index layers in the portion overlapping the second region 412.

[0103] The metal layer 609 is provided in the first region 411 and the second region 412, and absorbs a portion of the light generated in the active layer 404. For example, the metal layer 609 is a Cr layer, and the thickness of the metal layer 609 is 20 nm. The metal layer 609 may also be provided outside the emission region 413 in a plan view.

[0104] The other configurations are the same as in the fourth embodiment.

[0105] In the sixth embodiment, the reflectance of the portion of the upper reflector 608 that overlaps with the first region 411 in a plan view, as seen from the active layer 404 side, is higher than the reflectance of the portion of the upper reflector 608 that overlaps with the second region 412 in a plan view, as seen from the active layer 404 side. For example, the reflectance of the portion of the upper reflector 608 that overlaps with the first region 411 in a plan view, as seen from the active layer 404 side, is 0.9999, and the reflectance of the portion of the upper reflector 608 that overlaps with the second region 412 in a plan view, as seen from the active layer 404 side, is 0.9994. As a result, the oscillation threshold for higher-order modes becomes higher than the oscillation threshold for single-mode in the in-plane transverse direction, and the surface-emitting laser 6 operates in single-mode. In addition, because the metal layer 609 absorbs a portion of the light, the optical output of the surface-emitting laser 6 can be suppressed. For example, the optical output of the surface-emitting laser 6 can be set to a range of sub-μW to several tens of μW, which is suitable for eye safety. In other words, according to the sixth embodiment, it is possible to achieve both eye-safe operation and single-mode operation.

[0106] Next, a method for manufacturing the surface-emitting laser 6 according to the sixth embodiment will be described.

[0107] First, the process up to the formation of the lower electrode 441 and the upper electrode 442 is carried out in the same manner as in the fourth embodiment. Next, a multilayer reflecting mirror 607 is formed on the transparent conductive layer 443. In forming the multilayer reflecting mirror 607, in order to make the transparent conductive layer 443 a node of the standing wave 432, first a Ta2O5 layer for phase adjustment is formed, and then SiO2 layers and Ta2O5 layers are stacked alternately for 10.5 periods with an optical thickness of λ / 4. Furthermore, a resist is formed in the region that will become the first region 411, and using this resist as a mask, a Ta2O5 layer with an optical thickness of λ / 4 is formed on the outermost SiO2 layer. In this way, the multilayer reflecting mirror 607 is formed.

[0108] Next, a metal layer 609 is formed on the multilayer reflecting mirror 607.

[0109] In this way, the surface-emitting laser 6 according to the sixth embodiment can be manufactured.

[0110] [5th ​​calculation example] Next, a calculation example (the fifth calculation example) performed with respect to the sixth embodiment will be described. In the fifth calculation example, a laminate consisting of the lower reflector 402, resonator 406, multilayer reflector 607, and metal layer 609 of the sixth embodiment was used as a model. Furthermore, each layer was assumed to be formed as a solid. The multilayer reflector 607 is a multilayer reflector with a period of 10.5 periods in the portion overlapping the first region 411 and a period of 11 periods in the portion overlapping the second region 412. The reflectance of the upper reflector 608 as seen from the active layer 404 was calculated when the film thickness of the Cr layer, which is the metal layer 609, was changed. Calculations were also performed for a model in which the period of the multilayer reflector 607 in the portion overlapping the first region 411 was 10.5 periods, and the period in the portion overlapping the second region 412 was 10.5 periods or 10 periods. The results are shown in Figure 16.

[0111] When the thickness of the Cr layer is 20 nm, the reflectivity in the portion overlapping the second region 412 is lower not only in the model with 11 periods (point A in Figure 16, corresponding to the sixth embodiment) but also in the model with 10 periods (point B in Figure 16) than in the model with 10.5 periods (point C in Figure 16). In other words, the reflectivity in the portion overlapping the second region 412 can be reduced not only in the model where the number of high refractive index layers in the portion overlapping the second region 412 is increased by one layer compared to the portion overlapping the first region 411, but also in the model where the number of high refractive index layers in the portion overlapping the second region 412 is decreased by one layer.

[0112] (Modified version of the sixth embodiment) Next, a modified version of the sixth embodiment will be described. The modified version differs from the sixth embodiment mainly in the configuration of the multilayer mirror. Figure 17 is a schematic cross-sectional view showing a surface-emitting laser according to a modified version of the sixth embodiment.

[0113] As shown in Figure 17, in the surface-emitting laser 6A according to a modification of the sixth embodiment, the upper reflector 608 has a multilayer reflector 607A instead of the multilayer reflector 607. On the emission surface 610A of the multilayer reflector 607A, similar to the sixth embodiment, there are nodes of the standing wave 432 in the first region 411 and antinodes of the standing wave 432 in the second region 412. For example, the multilayer reflector 607A includes 11 high refractive index layers and 10 low refractive index layers in the portion overlapping the first region 411, and includes 10 high refractive index layers and 10 low refractive index layers in the portion overlapping the second region 412. In other words, the multilayer reflector 607 is composed of a dielectric including 10.5 period high refractive index layers and low refractive index layers in the portion overlapping the first region 411, and is composed of a dielectric including 10 period high refractive index layers and low refractive index layers in the portion overlapping the second region 412.

[0114] The other configurations are the same as in the sixth embodiment.

[0115] As explained in the fifth calculation example, in the modified version of the sixth embodiment, the reflectance of the portion of the upper reflector 608 that overlaps with the first region 411 in a plan view, as seen from the active layer 404 side, is higher than the reflectance of the portion of the upper reflector 608 that overlaps with the second region 412 in a plan view, as seen from the active layer 404 side. Therefore, as with the sixth embodiment, both eye-safe and single-mode operation can be achieved.

[0116] (Seventh Embodiment) Next, a seventh embodiment will be described. The seventh embodiment relates to a surface-emitting laser. Figure 18 is a schematic cross-sectional view showing a surface-emitting laser according to the seventh embodiment. The seventh embodiment corresponds to another specific example of the first embodiment.

[0117] The surface-emitting laser 7 according to the seventh embodiment is a surface-emitting laser with a wavelength λ of 650 nm using GaAs. As shown in Figure 18, the surface-emitting laser 7 includes a substrate 701, a lower reflector 702 (second reflector), a lower spacer layer 703, an active layer 704, an upper spacer layer 705, and an upper reflector 708 (first reflector). The upper reflector 708 includes a multilayer reflector 707 and a metal layer 709. The surface-emitting laser 7 further includes a current-constricting layer 723, a lower electrode 741, an upper electrode 742, a contact layer 743, and an etching stop layer 744. The lower reflector 702 is provided on the substrate 701, the lower spacer layer 703 is provided on the lower reflector 702, and the active layer 704 is provided on the lower spacer layer 703. An upper spacer layer 705 is provided on the active layer 704, a multilayer reflector 707 is provided on the upper spacer layer 705, and an etching stop layer 744 is provided on the multilayer reflector 707. The resonator 706 is formed from the lower spacer layer 703, the active layer 704, and the upper spacer layer 705. The metal layer 709 is provided on the exit surface 710 of the multilayer reflector 707 opposite to the resonator 706 via the etching stop layer 744.

[0118] The substrate 701 is, for example, a GaAs substrate.

[0119] The lower reflector 702 is a multilayer reflector composed of semiconductors, for example, a high refractive index layer and a low refractive index layer with a period of 55.5. For example, the high refractive index layer is Al 0.50 Ga 0.50 The layer is As, and the low refractive index layer is Al 0.95 Ga 0.05 This is an As layer. The optical thickness of the high-refractive-index and low-refractive-index layers for one period is λ / 2.

[0120] The multilayer mirror 707 has the same configuration as the multilayer mirror 107. That is, the multilayer mirror 707 has a low refractive index layer and a high refractive index layer, and the low refractive index layer and the high refractive index layer are alternately laminated. The low refractive index layer has a first refractive index, and the high refractive index layer has a second refractive index higher than the first refractive index. The multilayer mirror 707 is, for example, a multilayer mirror composed of a semiconductor including 34.5 cycles of high refractive index layers and low refractive index layers. For example, the high refractive index layer is Al 0.50 Ga 0.50 As layer, and the low refractive index layer is Al 0.95 Ga 0.05 As layer. The optical thickness of one cycle of the high refractive index layer and the low refractive index layer is λ / 2. For example, the multilayer mirror 707 includes 34 Al 0.50 Ga 0.50 As layers and 35 Al 0.95 Ga 0.05 As layers.

[0121] The active layer 704 has a multiple quantum well structure including a plurality of GaInP layers and AlGaInP layers. The lower spacer layer 703 is an n-type AlGaInP layer, and the upper spacer layer 705 is a p-type AlGaInP layer. The etching stop layer 744 is a p-type GaInP layer, and the contact layer 743 is a p-type GaAs layer. The contact layer 743, the etching stop layer 744, the multilayer mirror 707, the upper spacer layer 705, the active layer 704, and a part of the lower spacer layer 703 are etched to form a mesa structure. The film thickness of the etching stop layer 744 is about 10 nm, which corresponds to an optical thickness of about 0.05λ.

[0122] The current confinement layer 723 includes a conductive region 721 and an insulating region 722. The conductive region 721 is surrounded by the insulating region 722. For example, the current confinement layer 723 is formed by using the third cycle low refractive index layer from the active layer 704 side of the multilayer mirror 707 as an AlAs layer and subjecting this AlAs layer to steam oxidation. That is, for example, the conductive region 721 is an AlAs layer (low refractive index layer), and the insulating region 722 is Al x O yThis is a layer. The current-constricting layer 723 limits the region in the active layer 704 where current flows. When carriers are injected into the active layer 704, a standing wave of light 732 is generated perpendicular to the substrate surface (main surface) of the substrate 701 at a wavelength λ (650 nm) defined by the resonator 706. In the seventh embodiment, the center of the region overlapping with the conductive region 721 of the active layer 704 in a plan view is defined as the emission center 720, and light is emitted towards the multilayer reflector 707.

[0123] Figure 18 schematically shows the positions of the antinodes and nodes of the standing wave 732. In the seventh embodiment, the resonator 706 is constructed with a thickness such that the standing wave 732 is generated at a wavelength λ of 650 nm. To obtain a high gain, the active layer 704 is located at the antinode of the standing wave 732 where the light intensity is strong. Also, there are nodes of the standing wave 732 on the exit surface 710 of the multilayer mirror 707. For example, a low refractive index layer with an optical thickness of λ / 4 constitutes the exit surface 710. That is, in the direction of light emission, the multilayer mirror 707 is located on the low refractive index layer (Al 0.95 Ga 0.05 It is terminated at the As layer.

[0124] The emission surface 710 of the multilayer reflecting mirror 707 has an emission region 713 from which light generated in the active layer 704 is emitted. The emission region 713 also has a first region 711 that includes the emission center 720 in a plan view, and a second region 712 located around the first region 711. The second region 712 surrounds the first region 711, for example. For example, the first region 711 is a circular region, and the second region 712 is an annular region. The first region 711 is a region with high light intensity of the lateral fundamental mode 731 that includes the emission center 720.

[0125] The metal layer 709 is provided in the first region 711 via an etching stop layer 744 and absorbs a portion of the light generated in the active layer 704. The metal layer 709 is, for example, a Cr layer. The thickness of the metal layer 709 is, for example, 40 nm.

[0126] The lower electrode 741 has an AuGe alloy layer in direct contact with the substrate 701, a Ni layer beneath this AuGe alloy layer, and an Au layer beneath this Ni layer. The upper electrode 742 has an AuZn alloy layer formed on the contact layer 743, and an Au layer above this AuZn alloy layer. When a voltage is applied between the lower electrode 741 and the upper electrode 742, a current flows through the active layer 704.

[0127] In the seventh embodiment, the reflectance of the portion of the upper reflector 708 that overlaps with the first region 711 in a plan view, as seen from the active layer 704 side, is higher than the reflectance of the portion of the upper reflector 708 that overlaps with the second region 712 in a plan view, as seen from the active layer 704 side. For example, the reflectance of the portion of the upper reflector 708 that overlaps with the first region 711 in a plan view, as seen from the active layer 704 side, is 0.9929, and the reflectance of the portion of the upper reflector 708 that overlaps with the second region 712 in a plan view, as seen from the active layer 704 side, is 0.9837. As a result, the oscillation threshold for higher-order modes becomes higher than the oscillation threshold for single-mode in the in-plane transverse direction, and the surface-emitting laser 7 operates in single-mode. In addition, because the metal layer 709 absorbs a portion of the light, the optical output of the surface-emitting laser 7 can be suppressed. For example, the optical output of the surface-emitting laser 7 can be set to a range of sub-μW to several tens of μW, which is suitable for eye safety. In other words, according to the seventh embodiment, it is possible to achieve both eye-safe operation and single-mode operation.

[0128] Next, a method for manufacturing the surface-emitting laser 7 according to the seventh embodiment will be described.

[0129] First, a lower reflector 702, a lower spacer layer 703, an active layer 704, an upper spacer layer 705, an upper reflector 708, an etching stop layer 744, and a contact layer 743 are formed on the substrate 701 using an MOCVD apparatus.

[0130] Next, using photolithography and dry etching, a mesa structure is formed in the contact layer 743, etching stop layer 744, upper reflector 708, upper spacer layer 705, active layer 704, and a portion of the lower spacer layer 703, such that a portion of the lower spacer layer 703 remains in the thickness direction.

[0131] Next, the AlAs layer in the upper reflector 708 is selectively oxidized by water vapor oxidation to form the current-constricted layer 723.

[0132] Next, the entire wafer is passivated with an insulating film (not shown) to remove the insulating film on top of the mesa structure. Then, the contact layer 743 is etched until the etching stop layer 744 is exposed, forming an opening in the contact layer 743. Next, within the opening, a metal layer 709 is formed on top of the etching stop layer 744 in the region of high light intensity of the lateral fundamental mode 731, i.e., the first region 711. In addition, a lower electrode 741 is formed on the back surface of the substrate 701, and an upper electrode 742 is formed on top of the contact layer 743.

[0133] In this way, the surface-emitting laser 7 according to the seventh embodiment can be manufactured.

[0134] Furthermore, the metal layer 709 may be made of another metal that can provide ohmic contact, and a metal layer may be formed in the second region 712 with a thickness that does not result in excessively high reflectivity. In this case, the metal layer 709, the metal layer formed in the second region 712, and the upper electrode can all function together. With this structure, compared to the conventional structure in which the upper electrode is formed outside the output region, the metal layer makes it easier to uniformly inject current into the output region, and makes it easier to operate in single mode in the lateral direction.

[0135] [6th calculation example] Next, a calculation example (the sixth calculation example) performed with respect to the seventh embodiment will be described. In the sixth calculation example, a laminate consisting of the lower reflector 702, resonator 706, multilayer reflector 707, and metal layer 709 of the seventh embodiment was used as a model. Furthermore, each layer was assumed to be formed as a solid. The multilayer reflector 707 is a 34.5 period dielectric multilayer reflector, with the exit surface 710 terminated by a low refractive index layer, forming a node of the standing wave 732. The reflectance and transmittance of the upper reflector 708 as seen from the active layer 704 were calculated when the thickness of the Cr layer, which is the metal layer 709, was changed. The results are shown in Figure 19. Figure 19(a) shows the relationship between the thickness of the Cr layer and the reflectance and transmittance of the upper reflector 708. Figure 19(b) shows the relationship between the thickness of the Cr layer and the transmittance ratio of the upper reflector 708, derived from Figure 19(a).

[0136] Here, Al 0.50 Ga 0.50 The refractive index of the As film is 3.32, Al 0.95 Ga 0.05 The calculations were performed using a refractive index of 3.05 for As, 3.35 for GaInP, and 3.1+3.33i for Cr. As shown in Figure 19, in the range of Cr layer thickness from 0 nm to 1-2 nm, the reflectivity decreases slightly as the Cr layer thickness increases, but in the range of Cr layer thickness greater than that, the reflectivity increases as the Cr layer thickness increases. Thus, by forming a Cr layer with a thickness of 2 nm or more, the reflectivity can be increased, and the light output can be weakened by absorption by the Cr layer. When the Cr layer thickness was 40 nm, the reflectance ratio was 1.00931 and the transmittance ratio was 0.0303.

[0137] The reflectance ratio varies depending on the number of pairs of multilayer mirrors, the refractive index, reflectance, and thickness of the first layer, and there may be a first layer thickness at which the reflectance ratio is less than 1 (Figures 7, 8, 13, 16, 19, etc.). In such cases, it is preferable to adjust the thickness of the first layer so that the reflectance ratio is 1 or greater. Furthermore, when a second region with low reflectance is provided around a first region where the first layer is located, the reflectance difference between the first and second regions can be made larger by setting the thickness of the first layer so that the reflectance ratio is 1 or greater.

[0138] The transmittance ratio decreases as the thickness of the first layer increases. In this disclosure, by forming a Cr layer with a thickness of about 10 nm to 20 nm or an Al layer with a thickness of about 20 nm to 30 nm as the first layer, the transmittance ratio can be reduced to 0.1 or less, enabling the realization of a lower-power light-emitting element.

[0139] (Eighth embodiment) Next, a projection device according to the eighth embodiment will be described with reference to Figure 20. Figure 20 is a diagram illustrating an example of the configuration of the projection device 1000 according to this embodiment. The projection device 1000 can draw an image by scanning a laser beam.

[0140] As shown in Figure 20, the projection device 1000 comprises a light source 1001 and an optical scanning unit 1002. The light source 1001 comprises one or more surface-emitting lasers according to any of the first to seventh embodiments or their modified forms.

[0141] If the light source 1001 contains one surface-emitting laser, the projection device 1000 projects a monochrome image onto the object 1003. If the light source 1001 contains two or more surface-emitting lasers, the projection device 1000 aligns the optical axes of each surface-emitting laser coaxially and emits them from the emission surface, and by changing the oscillation wavelength for each surface-emitting laser, it can project images of multiple colors onto the object 1003.

[0142] The optical scanning unit 1002 includes an element for scanning the laser light emitted from the light source 1001 and projecting it onto the object 1003. Such an element could be a biaxially movable MEMS (micro electro-mechanical systems) mirror or an element combining two biaxially movable MEMS mirrors. The optical scanning unit 1002 is an example of an optical element that adjusts the direction of propagation of the laser light emitted from the light source 1001.

[0143] During image generation, the intensity of the laser beam is modulated in accordance with the scanning of the optical scanning unit 1002, and the laser beam is irradiated onto the object 1003. In this way, an image can be generated directly on the object 1003.

[0144] (Ninth Embodiment) Next, a head-mounted display according to the ninth embodiment will be described with reference to Figures 21 and 22. Figure 21 is a perspective view illustrating an example of the configuration of the head-mounted display 60 according to this embodiment. Figure 22 is a cross-sectional view illustrating an example of the configuration of the head-mounted display 60.

[0145] The head-mounted display 60 is an example of a head-mounted display device that can be worn on a human head, and can take the form of, for example, eyeglasses. Hereafter, Head Mount Display will be abbreviated as HMD.

[0146] In Figure 21, the HMD60 is composed of a front 60a and temples 60b, each provided in a roughly symmetrical arrangement on the left and right sides. The front 60a can be made of, for example, a light guide plate 61, and the optical system, control device, etc., can be built into the temples 60b.

[0147] Figure 22 partially shows the configuration of the HMD60. Although Figure 22 illustrates the configuration for the left eye, the HMD60 has a similar configuration for the right eye.

[0148] The HMD60 comprises a control device 11, a light source unit 930, a light intensity adjustment unit 907, a movable device 13 having a reflective surface 14, a light guide plate 61, and a half mirror 62. The HMD60 is an example of a display device.

[0149] The light source unit 930 is a unit comprising a red laser light source, a green laser light source, and a blue laser light source, multiple collimating lenses, and multiple dichroic mirrors, all housed in an optical housing. In the light source unit 930, the three laser beams from the red, green, and blue laser light sources are combined by the dichroic mirrors, which act as a combining unit. The combined parallel light is emitted from the light source unit 930. The light source unit 930 is an example of a light source device.

[0150] The red laser light source comprises one or more surface-emitting lasers according to any of the first to seventh embodiments or their modifications, and emits red laser light. The green laser light source comprises one or more surface-emitting lasers according to any of the first to seventh embodiments or their modifications, and emits green laser light. The blue laser light source comprises one or more surface-emitting lasers according to any of the first to seventh embodiments or their modifications, and emits blue laser light. In the fourth to seventh embodiments or their modifications, the oscillation wavelength is specified, but the oscillation wavelength can be changed by selecting the semiconductor layer material and optical thickness.

[0151] Light from the light source unit 930 is adjusted in intensity by the light intensity adjustment unit 907 before being incident on the movable device 13. Based on signals from the control device 11, the movable device 13 moves the reflective surface 14 in the XY direction and scans the light from the light source unit 930 in two dimensions. The drive control of the movable device 13 is synchronized with the emission timing of the red laser light source, green laser light source, and blue laser light source.

[0152] The scanning light from the movable device 13 enters the light guide plate 61. The light guide plate 61 guides the scanning light to the half mirror 62 while reflecting it off its inner wall surface. The light guide plate 61 is made of a resin or the like that is transparent to the wavelength of the scanning light.

[0153] The half-mirror 62 reflects light from the light guide plate 61 to the back side of the HMD 60 and emits it towards the eyes of the wearer 63. The half-mirror 62 has, for example, a free-form surface shape. The image formed by the scanning light is projected onto the wearer's retina by reflection from the half-mirror 62. Alternatively, it is projected onto the wearer's retina by reflection from the half-mirror 62 and the lens effect of the crystalline lens in the eyeball. Furthermore, spatial distortion of the image is corrected by reflection from the half-mirror 62. The wearer 63 can view the image formed by light scanned in the XY direction.

[0154] Because a half-mirror 62 is used, the wearer 63 sees a superimposed image of the image produced by light from the outside and the image produced by the scanning light. By replacing the half-mirror 62 with a mirror, it is also possible to eliminate light from the outside and create a configuration in which only the image produced by the scanning light can be seen.

[0155] In this embodiment, compared to the case where an end-emitting laser is used as the light source, a smaller and lighter HMD can be realized with fewer components such as ND filters and lower power consumption.

[0156] (Tenth embodiment) Next, a biometric authentication device utilizing a person's pupil response according to the 10th embodiment will be described with reference to Figure 23. Figure 23 is a diagram illustrating an example of the configuration of the biometric authentication device according to this embodiment. The biometric authentication device 20 comprises a light source 21, an optical scanning unit 22, a first optical element 23, a second optical element 24, an image sensor 25, and a control device 27. The light source 21 comprises one or more surface-emitting lasers according to any of the first to seventh embodiments or their modified variations, and the light emitted from the light source 21 is incident on the optical scanning unit 22. The optical scanning unit 22 moves its reflective surface based on a signal from the control device 27 and scans the light from the light source 21. The scanning light from the optical scanning unit 22 is irradiated onto the pupil 26 via the first optical element 23 and the second optical element 24. The size of the pupil is controlled by the intensity of the light irradiated onto the pupil 26, and iris information is acquired by the image sensor 25. Then, the control device 27 acquires information about the pupil 26 of a person (living organism) based on the output of the image sensor 25. The biometric authentication device 20 is an example of a biological information acquisition device, the light source 21 is an example of a light source device, the image sensor 25 is an example of a light receiving device, and the control device 27 is an example of an information acquisition unit.

[0157] For example, the first optical element 23 is a waveguide that guides the light scanned by the optical scanning unit 22 to the second optical element 24, and the second optical element 24 is a mirror that changes the path of the light emitted from the first optical element 23 to the pupil 26. In this embodiment, the two optical elements are described separately, but other methods can be used as long as the optical element emits the scanned light to the pupil 26.

[0158] The light source 21 can be equipped with multiple elements; for example, it is a module implemented so that lasers of four wavelengths—red, blue, green, and infrared—are emitted coaxially. Because blue and green wavelengths elicit a more sensitive pupil response than other wavelengths, it is possible to narrow the pupil and obtain more detailed iris information. Furthermore, by using multiple wavelengths, biometric information for each wavelength of the iris can be obtained, resulting in higher authentication accuracy.

[0159] By using a surface-emitting laser according to any of the first to seventh embodiments or their variations, a biometric authentication device 20 that is eye-safe and highly accurate can be realized without the need for a filter to reduce the light output.

[0160] Although preferred embodiments have been described in detail above, the invention is not limited to the embodiments described above, and various modifications and substitutions can be made to the embodiments described above without departing from the scope of the claims. [Explanation of symbols]

[0161] 1, 2, 3, 4, 4A, 4B, 4C, 5, 5A, 6, 6A, 7-sided emitting laser 101, 401, 701 circuit boards 102, 402, 702 Lower reflectors 103, 403, 703 Lower spacer layer 104, 404, 704 active layer 105, 405, 705 Upper spacer layer 106, 406, 706 resonator 107, 207, 307, 407, 407B, 407C, 507, 607, 607a, 707 Multilayer reflector 108, 208, 308, 408, 508, 608, 708 Upper reflector 109, 209a, 209b, 309, 409, 409b, 409c, 409d, 509, 509a, 509b, 509c, 509d, 609, 709 Metal layer 110, 210, 310, 410, 410B, 410C, 510, 610, 610A, 710 Output surface 111, 411, 711 1st area 112, 412, 712 2nd area 113, 413, 713 Output area 120, 420, 720 Output center [Prior art documents] [Patent Documents]

[0162] [Patent Document 1] Japanese Patent Publication No. 2019-153779

Claims

1. A surface-emitting laser, The first reflecting mirror, A resonator including an active layer, The second reflector, It has, The first reflector is, A multilayer reflecting mirror in which a first refractive index layer having a first refractive index and a second refractive index layer having a higher refractive index than the first refractive index are alternately stacked, A first layer provided on the first surface of the multilayer reflecting mirror opposite to the active layer, It has, The first surface has an emission region from which light generated in the active layer is emitted, The first layer is provided in a region including the emission center when viewed from a plane perpendicular to the first surface, and absorbs a portion of the light generated in the active layer. The light generated in the active layer and transmitted through the first layer is emitted. The resonator is provided between the first reflector and the second reflector. The aforementioned emission region is In a plan view from a direction perpendicular to the first surface, the first region includes the emission center, A second region located around the first region, It has, The first layer is provided in the first region, The reflectance of the portion of the first reflector that overlaps with the first region in the plan view, as viewed from the active layer side, is higher than the reflectance of the portion of the first reflector that overlaps with the second region in the plan view, as viewed from the active layer side. A light-emitting element characterized in that the first surface of the multilayer reflecting mirror in the second region has a node of a longitudinal mode standing wave contained in the light generated in the active layer.

2. A surface-emitting laser, The first reflecting mirror, A resonator including an active layer, The second reflector, It has, The first reflector is, A multilayer reflecting mirror in which a first refractive index layer having a first refractive index and a second refractive index layer having a higher refractive index than the first refractive index are alternately stacked, A first layer provided on the first surface of the multilayer reflecting mirror opposite to the active layer, It has, The first surface has an emission region from which light generated in the active layer is emitted, The first layer is provided in a region including the emission center when viewed from a plane perpendicular to the first surface, and absorbs a portion of the light generated in the active layer. The light generated in the active layer and transmitted through the first layer is emitted. The resonator is provided between the first reflector and the second reflector. The aforementioned emission region is In a plan view from a direction perpendicular to the first surface, the first region includes the emission center, A second region located around the first region, It has, The first layer is provided in the first region, The reflectance of the portion of the first reflector that overlaps with the first region in the plan view, as viewed from the active layer side, is higher than the reflectance of the portion of the first reflector that overlaps with the second region in the plan view, as viewed from the active layer side. The second region has a second layer, A light-emitting element characterized in that at least one of the film thickness or material differs between the first layer and the second layer.

3. The light-emitting element according to claim 2, characterized in that the first layer is thicker than the second layer.

4. The light-emitting element according to claim 2 or 3, characterized in that the real portion of the complex refractive index of the first layer is lower than the real portion of the complex refractive index of the second layer.

5. The light-emitting element according to any one of claims 2 to 4, characterized in that the first surface of the multilayer reflecting mirror in the second region has nodes of a longitudinal mode standing wave contained in the light generated in the active layer.

6. The light-emitting element according to any one of claims 2 to 4, characterized in that the first surface of the multilayer reflecting mirror in the second region has an antinode of a longitudinal mode standing wave contained in the light generated in the active layer.

7. The light-emitting element according to claim 6, characterized in that the first surface of the multilayer reflecting mirror in the first region has a node of the standing wave.

8. The light-emitting element according to claim 1, 5, 6, or 7, wherein the phase of the standing wave differs between the first region and the second region.

9. Assuming there is air on the multilayer reflecting mirror, the reflectance when light generated in the active layer is incident on the interface between the multilayer reflecting mirror and the air from the multilayer reflecting mirror side is R. ０ year, The reflectance when light generated in the active layer is incident on the interface between the multilayer reflector and the first layer from the multilayer reflector side is R. １ as, The thickness of the first layer is the reflectance ratio R １ / R ０ A light-emitting element according to any one of claims 1 to 8, characterized in that the thickness is such that the ratio is 1 or more.

10. Assuming that there is air on the multilayer reflecting mirror, the transmittance when light generated in the active layer is transmitted from the multilayer reflecting mirror to the air is I. ０ year, The transmittance when light generated in the active layer is transmitted from the multilayer reflecting mirror on which the first layer is formed into the air is defined as I １ as, The thickness of the first layer is the transmittance ratio I １ / I ０ A light-emitting element according to any one of claims 1 to 9, characterized in that the thickness is greater than 0 and less than or equal to 0.

1.

11. A light-emitting element according to any one of claims 1 to 10, characterized in that the light output is 0.01 μW or more and 100 μW or less.

12. A light source device characterized by comprising a light-emitting element according to any one of claims 1 to 11.

13. A display device characterized by comprising a light-emitting element according to any one of claims 1 to 11.

14. A head-mounted display characterized by comprising a light-emitting element according to any one of claims 1 to 11.

15. A light source device that irradiates living organisms with light, A light receiving device that receives reflected light from the aforementioned living organism, An information acquisition unit that acquires information about the living organism based on the output of the light receiving device, It has, The biometric information acquisition device is characterized by comprising a light-emitting element according to any one of claims 1 to 11.

Images