Light emitting device, distance measuring device and moving object

Abstract

To provide a light emitting device capable of generating an optical pulse having a short optical pulse width and a high peak value in the long wavelength region.SOLUTION: A light emitting device includes a first semiconductor light emitting element having a first active layer and a first resonator portion on a semiconductor substrate, and emitting first light, a second semiconductor light emitting element having a first reflecting mirror, a second resonator portion including a second active layer excited by the first light, and a second reflecting mirror stacked in this order on the first semiconductor light emitting element, and emitting second light, and a driving unit that injects a current into the first semiconductor light emitting element, and the oscillation wavelength of the second semiconductor light emitting element is longer than the oscillation wavelength of the first semiconductor light emitting element, the second semiconductor light emitting element includes a saturable absorbing layer between the second resonator portion and the second reflecting mirror, and the thickness L of the second active layer and the absorption coefficient α of the second active layer satisfy the following formula (1). 3.45≤α×L≤15 (1).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a light emitting device, a distance measuring device, and a moving object. [Background technology]

[0002] VCSELs (Vertical Cavity Surface Emitting Lasers) are known as light sources for LiDAR (Light Detection and Ranging) using the ToF (Time of Flight) method, which utilizes the time it takes for light to be irradiated onto an object and reflected back. VCSELs have the advantage of having little wavelength dependency on temperature.

[0003] In the above system, by increasing the peak value of the irradiated light pulse, it becomes easier for the light receiving side to distinguish between ambient light and the light pulse emitted by the system itself, and the S / N ratio can be increased, thereby extending the maximum measurable distance. On the other hand, from the viewpoint of eye safety, there is a limit to the peak value of the light pulse. The upper limit of the peak value from the viewpoint of eye safety depends on the width of the light pulse, and the narrower the width of the light pulse, the higher the peak value can be. Therefore, a light source that can generate a pulse with a short light pulse width and a high peak value is desirable as a light source to be applied to a LiDAR system.

[0004] As such a light source, Patent Document 1 proposes a high peak value pulse VCSEL having a saturable absorbing layer as a VCSEL that realizes an optical pulse with a narrower optical pulse width than the injected current pulse width and a high peak value.

[0005] In addition, the greater the power of the light source, the longer the measuring distance. Therefore, in recent years, from the perspective of eye safety, there has been a growing need for light sources that generate light pulses in the 1000 to 2000 nm wavelength band, which have a longer peak value, rather than light pulses in the 800 to 900 nm wavelength band.

[0006] However, there are various issues when fabricating VCSELs with wavelengths longer than 800-900 nm by current injection. For example, regrowth is required to create a current confinement structure, which is costly. Also, a large number of semiconductor DBR (Distributed Bragg Reflector) layers are required, and quaternary materials are often required, which results in poor heat dissipation and high electrical resistance. Furthermore, the gain of the active layer is low, making it difficult to significantly increase the number of active layers.

[0007] To solve these problems, Patent Document 2 proposes a light-emitting device in which the output light of a short-wavelength VCSEL with a wavelength of 980 nm is used as pumping light, and a long-wavelength VCSEL fabricated on top of it is optically excited to oscillate. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2022 / 244674 [Patent Document 2] Special Publication No. 10-501927 Summary of the Invention [Problem to be solved by the invention]

[0009] However, even if the configuration described in Patent Document 1 for generating a pulse with a high peak value immediately after the start of laser oscillation is applied to the optically pumped VCSEL described in Patent Document 2, it is difficult to realize an optical pulse with a high peak value in the long wavelength region exceeding 1000 nm.

[0010] An object of the present invention is to provide a light emitting device capable of generating an optical pulse having a short optical pulse width and a high peak value in the long wavelength region, and a distance measuring device and a mobile object using such a light emitting device. [Means for solving the problem]

[0011] According to one aspect of the present invention, there is provided a light-emitting device comprising: a first semiconductor light-emitting element having a first active layer and a first resonator portion on a semiconductor substrate and emitting a first light; a second semiconductor light-emitting element having a first reflecting mirror, a second resonator portion including a second active layer excited by the first light, and a second reflecting mirror stacked in this order on the first semiconductor light-emitting element, emitting a second light; and a driving portion that injects a current into the first semiconductor light-emitting element, wherein the oscillation wavelength of the second semiconductor light-emitting element is longer than the oscillation wavelength of the first semiconductor light-emitting element, and the second semiconductor light-emitting element includes a saturable absorbing layer between the second resonator portion and the second reflecting mirror, and a thickness L of the second active layer and an absorption coefficient α of the second active layer satisfy the following formula (1). 3.45≦α×L≦15 …(1) Effect of the Invention

[0012] According to the present invention, it is possible to realize a light emitting device capable of generating an optical pulse with a short optical pulse width and a high peak value in the long wavelength region, as well as a distance measuring device and a mobile object using such a light emitting device. [Brief description of the drawings]

[0013] [Figure 1] 1 is a schematic cross-sectional view showing a light emitting device according to a first embodiment. [Diagram 2] 1 is a graph showing the relationship between the thickness of the active layer in a high peak value VCSEL and the peak intensity of an optical pulse at the start of oscillation. [Diagram 3] 1 is a graph showing the relationship between the product α×L and the peak intensity of an optical pulse at the start of oscillation in a high peak-value VCSEL. [Figure 4] 1 is a graph showing the relationship between the thickness of the active layer and the wavelength difference between adjacent longitudinal modes in a high peak value VCSEL. [Diagram 5] FIG. 11 is a schematic cross-sectional view showing a high peak value type VCSEL in a light emitting device according to a second embodiment. [Figure 6]1 is a graph showing the relationship between the amount of excitation light absorbed in an active layer in a high peak value VCSEL and the position in the thickness direction of the active layer. [Figure 7] FIG. 11 is a schematic cross-sectional view showing a high peak value type VCSEL in a light emitting device according to a third embodiment. [Figure 8] FIG. 11 is a schematic cross-sectional view showing a light emitting device according to a fourth embodiment. [Figure 9] FIG. 13 is a block diagram showing a schematic configuration of a distance measuring device according to a fifth embodiment. [Figure 10] FIG. 13 is a block diagram showing a schematic configuration of a distance measuring device according to a sixth embodiment. [Figure 11] FIG. 13 is a schematic cross-sectional view showing an example of the configuration of a surface-emitting laser array in a distance measuring device according to a sixth embodiment. [Figure 12] FIG. 13 is a diagram illustrating an example of the configuration of a moving body according to the seventh embodiment. [Figure 13] FIG. 1 is a schematic cross-sectional view showing a light-emitting device according to a reference embodiment. [Figure 14] 11 is a graph showing the relationship between the excitation rate of a saturable absorbing layer and the shape of an optical pulse emitted from a high peak value VCSEL in a light emitting device according to a reference embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] [Reference form] The present inventors have found that in a device in which the output light of the short-wavelength VCSEL described in Patent Document 2 is used as pumping light, if the long-wavelength VCSEL excited by the pumping light is simply replaced with the high-peak VCSEL described in Patent Document 1, a new problem arises. Due to this problem, even if the configuration for generating a high-peak pulse immediately after the start of laser oscillation described in Patent Document 1 is applied to the VCSEL using optical pumping in Patent Document 2, it is difficult to realize a high-peak VCSEL in the long-wavelength region exceeding 1000 nm.

[0015] In this embodiment, a new problem that arises when the long-wavelength VCSEL in the device described in Patent Document 2 is simply replaced with the high peaked VCSEL described in Patent Document 1 will be described with reference to FIGS.

[0016] Fig. 13 is a schematic cross-sectional view showing a light emitting device 900 according to this embodiment. The light emitting device 900 according to this embodiment shown in Fig. 13 has a structure in which an excitation VCSEL 901 having an oscillation wavelength of 940 nm and a high peak VCSEL 902 having an oscillation wavelength of 1550 nm are stacked. The light emitting device 900 has the excitation VCSEL 901 at the bottom and the high peak VCSEL 902 at the top.

[0017] The excitation VCSEL 901 has a substrate 903, a lower reflecting mirror 904, an active layer 905, an upper reflecting mirror 906, and a current confinement portion 907. The lower reflecting mirror 904, the active layer 905, and the upper reflecting mirror 906 are stacked in this order on the substrate 903. The current confinement portion 907 is provided in the upper reflecting mirror 906. A current is injected into the excitation VCSEL 901 by an upper electrode (not shown) on the upper reflecting mirror 906 and a lower electrode (not shown) below the substrate 903. Carriers injected from the upper electrode are supplied to only the center portion of the active layer 905 by the current confinement portion 907 in the upper reflecting mirror 906. The excitation VCSEL 901 oscillates upon current injection to generate laser light. The laser light is resonated by the upper reflecting mirror 906 and the lower reflecting mirror 904, is emitted, and is released to the top of the excitation VCSEL 901 as excitation light 914.

[0018] The high peak value VCSEL 902 has a lower reflecting mirror 908, a spacer portion 909, a resonator portion 910, and an upper reflecting mirror 911. The lower reflecting mirror 908, the spacer portion 909, the resonator portion 910, and the upper reflecting mirror 911 are layered in this order from the excitation VCSEL 901 side. A saturable absorbing layer 912 is disposed in the spacer portion 909. An active layer 913 is disposed in the resonator portion 910.

[0019] In the high peak value VCSEL 902, when the saturable absorbing layer 912 is directly excited by the pump light 914 emitted from the pump VCSEL 901, the pulse intensity of the optical pulse emitted from the high peak value VCSEL 902 decreases. This decrease in pulse intensity will be further described with reference to FIG.

[0020] 14 is a graph showing the relationship between the excitation rate of the saturable absorbing layer 912 and the shape of the optical pulse emitted from the high peak value VCSEL 902. In FIG. 14, the horizontal axis represents time, and the vertical axis represents the optical intensity of the light emitted from the high peak value VCSEL 902.

[0021] 14, it can be seen that as the excitation rate at which the saturable absorbing layer 912 is excited by the excitation light 914 increases, the maximum intensity of the optical pulse emitted from the high peak value VCSEL 902 decreases. This decrease in the maximum intensity of the optical pulse is due to the following reason. That is, due to the absorption of the excitation light 914 in the saturable absorbing layer 912, the time it takes for the carriers in the saturable absorbing layer 912 to increase to the transparent carrier density becomes shorter than when the excitation light 914 is not absorbed. Accordingly, the time during which carriers can be stored in the active layer 913 becomes shorter, and as a result, the maximum intensity of the optical pulse emitted from the high peak value VCSEL 902 decreases.

[0022] In contrast, in the following embodiment, a light emitting device is described that includes a semiconductor light emitting element that solves the problems of the configuration shown in FIG. 13 described above and can generate light pulses with short light pulse widths and high peak values ​​in the long wavelength region.

[0023] [First embodiment] A light emitting device according to a first embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a schematic cross-sectional view showing a light emitting device according to this embodiment.

[0024] As shown in Fig. 1, the light emitting device 100 according to this embodiment is a VCSEL having a pumping VCSEL 101 with an oscillation wavelength of 940 nm at the bottom and a high peak value VCSEL 102 with an oscillation wavelength of 1550 nm at the top. The light emitting device 100 has a structure in which the high peak value VCSEL 102 is stacked on the pumping VCSEL 101. The pumping VCSEL 101 is a first semiconductor light emitting element that emits pumping light 113 for exciting the high peak value VCSEL 102. The high peak value VCSEL 102 is a second semiconductor light emitting element that is pumped by the pumping light 113 and emits a high peak value optical pulse.

[0025] The oscillation wavelength of the pump VCSEL 101 and the oscillation wavelength of the high peak VCSEL 102 are not limited to the above wavelengths. The oscillation wavelength of the pump VCSEL 101 may be a short wavelength band, for example, a wavelength band of 800 to 900 nm. The oscillation wavelength of the high peak VCSEL 102 may be a long wavelength band, for example, a wavelength band of 1000 to 2000 nm, as long as it is longer than the oscillation wavelength of the pump VCSEL 101.

[0026] First, the configuration of the excitation VCSEL 101 will be described. The excitation VCSEL 101 has a semiconductor substrate 103, a lower DBR layer 104 which is a reflector, a resonator portion 105, an upper DBR layer 110 which is a reflector, electrodes 150, 151, and a protective film 160. The lower DBR layer 104 is provided on the semiconductor substrate 103. The resonator portion 105 is provided on the lower DBR layer 104. The upper DBR layer 110 is provided on the resonator portion 105.

[0027] The resonator section 105 is composed of an n-type layer 107 provided on the lower DBR layer 104, an active layer 108 provided on the n-type layer 107, and a p-type layer 109 provided on the active layer 108. The active layer 108 has a non-doped layer and three quantum wells 111 provided in the non-doped layer. The resonator section 105 is composed of a pin junction composed of the n-type layer 107, the active layer 108 including the non-doped layer, and the p-type layer 109. Each of the three quantum wells 111 included in the active layer 108 may be composed of four InGaAs layers each having a thickness of 8 nm sandwiched between AlGaAs barrier layers each having a thickness of 10 nm. The n-type layer 107 may be composed of an n-type GaAs layer, the p-type layer 109 may be composed of a p-type GaAs layer, and the non-doped layer of the active layer 108 may be composed of a non-doped GaAs layer. An oxide constriction layer 112 is provided within the upper DBR layer 110 .

[0028] The active layer 108, p-type layer 109, and upper DBR layer 110 above the n-type layer 107 are processed into a mesa shape to form a mesa portion 114. An electrode 150 electrically connected to the upper DBR layer 110 is provided on the upper DBR layer 110. An electrode 151 electrically connected to the semiconductor substrate 103 by an ohmic contact is provided on the back surface of the semiconductor substrate 103. A driver that injects a drive current to drive the excitation VCSEL 101 into the excitation VCSEL 101 is electrically connected to the electrodes 150 and 151.

[0029] A protective film 160 is provided on the upper surface of n-type layer 107 exposed by processing active layer 108, p-type layer 109, and upper DBR layer 110 into a mesa shape, and on the upper surface of mesa portion 114 excluding the side surface of mesa portion 114 and at least a part of the surface of electrode 150. Protective film 160 is provided for the purpose of preventing deterioration of the semiconductor surface.

[0030] The semiconductor substrate 103 may be, for example, an n-type GaAs substrate. The lower DBR layer 104 may be, for example, an Al 0.1 GaAs layer and Al 0.9A laminate with a GaAs layer counts as one pair, and 35 pairs of these may be laminated to form the lower DBR layer 104. Here, λc is the center wavelength of the high reflection band of the lower DBR layer 104, which is 940 nm in this embodiment.

[0031] The upper DBR layer 110 is, for example, an Al 0.1 GaAs layer and Al 0.9 The upper DBR layer 110 may be constructed by stacking 20 pairs of a GaAs layer and a 30 nm thick Al layer. 0.98 The oxidized constriction layer 112 is formed by oxidizing a part of the GaAs layer. The oxidized constriction layer 112 is, for example, Al 0.98 It can be formed by oxidizing the GaAs layer with water vapor in the lateral direction from the side surface of the mesa portion 114. The oxidized constriction layer 112 has a non-oxidized portion in the center of the mesa portion 114 and an oxidized portion of a predetermined length in the vicinity of the side wall of the mesa portion 114. As a result, the current injected into the pumping VCSEL 101 flows only through the non-oxidized portion, and therefore only the portion of the pumping VCSEL 101 that overlaps with the center portion of the mesa portion 114 in a plan view oscillates as a laser.

[0032] Laser light generated in the pumping VCSEL 101 is emitted from the upper DBR layer 110 side and enters the high peak value VCSEL 102 stacked on the pumping VCSEL 101 as pumping light 113. A mesa portion 114 in the pumping VCSEL 101 functions as a light emitting portion that emits the pumping light 113.

[0033] Next, the configuration of the high peak value VCSEL 102 optically pumped by the pump light 113 will be described. The high peak value VCSEL 102 has a lower DBR layer 200 as a reflector, an active layer 201, a carrier block layer 202, a saturable absorbing layer 203, an upper DBR layer 204 as a reflector, a semiconductor substrate 205, and an AR coating 206. The lower DBR layer 200 is disposed on a mesa portion 114 including the active layer 108, the p-type layer 109, and the upper DBR layer 110 of the pump VCSEL 101. The active layer 201 is disposed on the lower DBR layer 200. The carrier block layer 202 is disposed on the active layer 201. The saturable absorbing layer 203 is disposed on the carrier block layer 202. The upper DBR layer 204 is disposed on the saturable absorbing layer 203. The semiconductor substrate 205 is disposed on the upper DBR layer 204. The AR coating 206 is provided on the semiconductor substrate 205. The pump light 113 is incident on the high peak VCSEL 102 from the lower DBR layer 200 side.

[0034] The lower DBR layer 200 may be, for example, a SiO2 / TiO2 layer, and may be constructed by laminating seven pairs of laminates each consisting of a SiO2 layer and a TiO2 layer with an optical film thickness of 1 / 4λd. Here, λd is the central wavelength of the high reflection band of the lower DBR layer 200, which is 1550 nm in this embodiment.

[0035] The resonator section is a layer between the lower DBR 200 and the upper DBR 204. The active layer 201 constitutes the resonator section. The active layer 201 can also constitute the resonator section together with other semiconductor layers stacked above and below it. In this embodiment, the resonator section is constituted by the active layer 201, the carrier block layer 202, and the saturable absorbing layer 203. In the present invention, the active layer is a region in the resonator where population inversion occurs due to the excitation light. In this embodiment, the active layer 201 is a layer constituted by a layer having a band gap smaller than the photon energy of the excitation light 113, and is located on the incidence side of the excitation light 113 in the resonator than the saturable absorbing layer 203. The saturable absorbing layer 203 is located on the farther side from the incidence side of the excitation light 113 than the active layer 201. The active layer 201 can have, for example, a barrier layer made of InGaAsP and a plurality of quantum well layers made of InGaAs provided in the barrier layer. Specifically, the active layer 201 may be configured to have a quantum well structure in which five InGaAs quantum well layers, each having a thickness of 8 nm, are arranged in an InGaAsP barrier layer, and to have a thickness of 3.2 μm. The thickness of the active layer 201 is not limited to this, and may be determined as described below. In this case, the position of the InGaAs quantum well layer is the position of an antinode of a standing wave generated in the active layer 201. Specifically, the positions of the five InGaAs quantum well layers in the thickness direction of the active layer 201 are as follows, assuming that the end of the active layer 201 where the excitation light 113 is incident is 0 nm. That is, the first layer is near 686 nm, the second layer is near 1143 nm, the third layer is near 1600 nm, the fourth layer is near 2057 nm, and the fifth layer is near 2971 nm. The center of gravity of these five InGaAs quantum well layers is located at the center of the active layer 201 in the thickness direction. Thus, the multiple quantum well layers in the active layer 201 are located at the antinode positions of the standing wave generated in the active layer 201, and the center of gravity of the multiple quantum well layers is located at the center in the thickness direction of the active layer 201. In this embodiment, as an example of the active layer 201, a layer composed of layers having a band gap smaller than the photon energy of the excitation light 113 is used, but the present invention is not limited to this, and the active layer 201 may partially include a layer having a band gap larger than the photon energy of the excitation light 113.In that case, the thickness of the active layer 201 is the total thickness of only the layers having a band gap smaller than the photon energy of the excitation light 113 .

[0036] The thickness of 3.2 μm of the active layer 201 that can be configured as described above is thicker than the thickness of a typical VCSEL configuration. Such a relatively thick active layer 201 is a configuration for solving problems that arise when a high peak value VCSEL 102 is used as an optically pumped VCSEL. This point will be described in detail below.

[0037] A carrier block layer 202 having an optical film thickness of 1 / 2 λd and a saturable absorbing layer 203 are laminated in this order on the active layer 201. The carrier block layer 202 serves to prevent carriers generated in the active layer 201 by optical excitation with the excitation light 113 from flowing into the saturable absorbing layer 203. The saturable absorbing layer 203 is disposed on the opposite side of the active layer 201 to the excitation VCSEL 101. That is, the saturable absorbing layer 203 is provided between the active layer 201 and the upper DBR layer 204.

[0038] The carrier blocking layer 202 is provided between the active layer 201 and the saturable absorbing layer 203. The carrier blocking layer 202 may be composed of, for example, an InP layer.

[0039] The saturable absorbing layer 203 may have, for example, a barrier layer made of InGaAsP that constitutes the active layer 201, and a plurality of quantum well layers made of InGaAs provided in the barrier layer. Specifically, the saturable absorbing layer 203 may be configured to have a quantum well structure in which the barrier layer is made of InGaAsP and four InGaAs quantum well layers with a thickness of 8 nm are arranged in the barrier layer.

[0040] The upper DBR layer 204 arranged on the saturable absorbing layer 203 is, for example, an InP / InGaAsP layer, and can be constructed by stacking multiple pairs of layers, each pair being a stack of an InP layer and an InGaAsP layer with an optical film thickness of 1 / 4λd.

[0041] The semiconductor substrate 205 disposed on the upper DBR layer 204 may be, for example, an InP substrate. An AR (Anti Reflection) coat 206 is provided on the surface of the semiconductor substrate 205 and reduces light reflection at the interface between the semiconductor substrate 205 and air.

[0042] As described in the above embodiment, if even a few percent of the total energy of the pump light directly excites the saturable absorbing layer, the pulse intensity of the short pulse at the start of oscillation obtained by the high peak value VCSEL decreases. For this reason, in this embodiment, the thickness of the active layer 201 is set so that the pump light 113 is sufficiently absorbed by the active layer 201. Specifically, the thickness of the active layer 201 is set to be thick enough to absorb the pump light 113 by the active layer 201, preferably 90% or more, more preferably 95% or more.

[0043] 2 is a graph showing the calculation results of the relationship between the thickness of the active layer 201 in the high peak value VCSEL 102 and the pulse intensity (peak intensity) of a light pulse, which is a short pulse at the start of oscillation emitted from the high peak value VCSEL 102. Here, the configuration including the materials of the pumping VCSEL 101 and the high peak value VCSEL 102 is as exemplified above. In FIG. 2, the horizontal axis indicates the thickness of the active layer 201, and the vertical axis indicates the peak intensity of the light pulse. The peak intensity of the light pulse is shown as a ratio relative to the case where the thickness of the active layer 201 is sufficiently thick and there is no effect of the pumping light 113 on the saturable absorbing layer 203, that is, the excitation rate of the saturable absorbing layer 203 is 0%, which is set to 1. Note that FIG. 2 shows the case where the absorption coefficient α described below is 15000 cm -1 The solid line shows the relationship when the absorption coefficient α is 10000 cm -1 When the relationship is 20000cm -1 The broken lines show the relationship when the absorption coefficient α is 4 cm. -1 The relationship in the case of a Yb:YAG (Ytterbium doped Yttrium Aluminum Garnet) crystal is shown by a dashed dotted line.

[0044] The absorption coefficient α of the active layer 201 for the excitation light 113 in the material used in this embodiment is 15000 cm -1 2, when the thickness of active layer 201 is reduced to 2.8 μm, the peak intensity decreases by 5%, and when the thickness is reduced to 2.3 μm, the peak intensity decreases by 10%, and it can be seen that the peak intensity decreases sharply as the thickness becomes thinner. Therefore, in this case, from the viewpoint of minimizing the decrease in the peak intensity of the optical pulse, the thickness of active layer 201 is preferably 2.3 μm or more, and more preferably 2.8 μm or more.

[0045] When light passes through a material with absorption coefficient α and length L, the transmittance I of light is expressed by the following equation. I = exp(-α × L)

[0046] Therefore, even if the absorption coefficient α of the active layer changes, the amount of transmitted light will be the same if the product of the absorption coefficient α of the active layer and the length (thickness) L of the active layer is constant. Therefore, the product α×L of the absorption coefficient α of the active layer and the thickness L of the active layer can provide a guideline for the preferred value of the thickness of the active layer.

[0047] FIG. 3 shows the absorption coefficient α of 15000 cm -1 2, where the horizontal axis represents the product α×L of the absorption coefficient α of active layer 201 and the thickness L of active layer 201. If the thickness of active layer 201 is expressed as the product α×L, a thickness of 2.3 μm corresponds to the product α×L of 3.45, and a thickness of 2.8 μm corresponds to the product α×L of 4.2.

[0048] Generally, the absorption coefficient α of the active layer 201 for light having a wavelength with energy larger than the band gap is in the range of 10,000 to 20,000 cm depending on the material composition, etc. -1 In FIG. 2, the absorption coefficient α of the active layer 201 for the excitation light 113 is 10000 cm -1 When 20000 cm -1The broken lines show the calculation results for the relationship between the thickness of active layer 201 and the peak intensity of the optical pulse for each of the cases. Considering this absorption coefficient α, from the same viewpoint as above, it can be said from FIG. 2 that the thickness of active layer 201 is preferably 1.8 μm or more, more preferably 2.4 μm or more, or preferably 3.5 μm or more. Note that these 1.8 μm, 2.4 μm, and 3.5 μm are each suitable for an absorption coefficient α of 20,000 cm -1 , 15000cm -1 , 10000cm -1 are the thicknesses of the active layer when the peak intensity is reduced by 10% in the cases of

[0049] On the other hand, a disadvantage of the thick active layer and long resonator length is that the interval between adjacent longitudinal modes becomes shorter. More specifically, when the interval between adjacent longitudinal modes becomes shorter, the difference in gain wavelength in the active layer and the difference in reflectance at the reflecting mirror become smaller between the longitudinal modes, and so-called mode hopping, in which oscillation moves to another longitudinal mode, becomes more likely to occur. The occurrence of mode hopping means that the oscillation wavelength of the laser changes. In the case of VCSEL, the wavelength difference between adjacent longitudinal modes, which is the wavelength at which the oscillation wavelength changes, generally exceeds 10 nm. When a light emitting device is used for distance measurement, a bandpass filter with a transmission wavelength band of several nm is usually placed on the light receiving side, so it is preferable to avoid the mode hopping phenomenon. In general, in order to avoid the mode hopping phenomenon, it is preferable to ensure a wavelength difference between adjacent longitudinal modes of 30 nm or more, and preferably 50 nm or more. This is because the wavelength difference between such adjacent longitudinal modes can provide a sufficient difference in the gain obtained in the active layer between adjacent longitudinal modes, and as a result, mode hopping can be suppressed.

[0050] FIG. 4 is a graph showing the relationship between the thickness of the active layer 201 in the high peak value VCSEL 102 and the wavelength difference between adjacent longitudinal modes. Here, the configuration including the materials of the pumping VCSEL 101 and the high peak value VCSEL 102 is as exemplified above. As shown in FIG. 4, when the thickness of the active layer 201 is 5 μm, the wavelength difference between adjacent longitudinal modes is 50 nm, and when the thickness of the active layer 201 is 10 μm, the wavelength difference between adjacent longitudinal modes is 30 nm. Therefore, the upper limit of the thickness of the active layer 201 is preferably 10 μm, and more preferably 5 μm. When the thickness of the active layer 201 is expressed as the product α×L of the absorption coefficient α of the active layer 201 and the length L, a thickness of 10 μm corresponds to the product α×L of 15, and a thickness of 5 μm corresponds to the product α×L of 7.5.

[0051] In the high peak value VCSEL 102 configured in this manner, the active layer 201 is optically excited by the excitation light 113 from the excitation VCSEL 101 below, and generates a high peak value, short optical pulse as the emitted light. The optical pulse is emitted to the outside of the high peak value VCSEL 102 from the semiconductor substrate 205 side.

[0052] The high peak value VCSEL 102 can emit light having a maximum peak value and a profile that converges to a stable value, which is a predetermined light intensity, after the maximum peak value. That is, in the high peak value VCSEL 102, laser oscillation is inhibited by the saturable absorbing layer 203 for a certain time from the incidence of the excitation light 113, and carriers exceeding the threshold carrier density are accumulated in the active layer 201. Here, the threshold carrier density is the carrier density that generates the gain required for laser oscillation. After that, in the high peak value VCSEL 102, when laser oscillation starts, carriers are rapidly consumed by stimulated emission and converge to a stable value. In this way, the high peak value VCSEL 102 accumulates more carriers in the active layer 201 than the threshold carrier density. Then, the carriers accumulated in the active layer 201 after the start of laser oscillation are converted to photons by stimulated emission. As a result, the high peak value VCSEL 102 can output a high peak value, short pulse light pulse.

[0053] As described above, in the light emitting device 100 according to the present embodiment, the following three elements are added to the high peak value VCSEL 102. The first of the three elements added to the high peak value VCSEL 102 is to place the saturable absorbing layer 203 on the opposite side of the active layer 201 from the excitation VCSEL 101. That is, the saturable absorbing layer 203 is provided between the resonator section formed by the active layer 201 and the upper DBR layer 204. The second is to make the active layer 201 thick enough that the amount of the excitation light 113 absorbed by the active layer 201 is preferably 90%, more preferably 95% or more. The third is to place the carrier block layer 202 between the resonator section and the saturable absorbing layer 203, that is, between the active layer 201 and the saturable absorbing layer 203. By adding at least the first and second of these three elements, and preferably the third, the amount of the excitation light 113 absorbed by the saturable absorbing layer 203 can be reduced. In this embodiment, in the case of the above-mentioned exemplary material composition, the amount of absorption of the excitation light 113 incident on the high peak value VCSEL 102 by the saturable absorbing layer 203 is suppressed to as low as 0.4%.

[0054] Regarding the second of the three factors, the thickness of active layer 201 can be defined as follows from the viewpoint of minimizing the decrease in peak intensity of the optical pulse described above and from the viewpoint of avoiding mode hopping.

[0055] First, the thickness L of the active layer 201 can be defined by the product α×L of the absorption coefficient α of the active layer 201 and the thickness L of the active layer 201. Specifically, the product α×L preferably satisfies the following formula (1), and more preferably satisfies the following formula (2). 3.45≦α×L≦15 …(1) 4.2≦α×L≦7.5 …(2)

[0056] Furthermore, the thickness L of the active layer 201 preferably satisfies the following formula (3), and more preferably satisfies the following formula (4). 2.3 μm ≦ L ≦ 10 μm … (3) 2.8μm≦L≦5μm …(4)

[0057] Thus, according to this embodiment, it is possible to suppress the decrease in peak intensity of the high peak value, short-pulse optical pulse emitted from the high peak value VCSEL 102. Therefore, according to this embodiment, it is possible to realize a light emitting device 100 that can generate an optical pulse with a short optical pulse width and a high peak value in the long wavelength region. By configuring the high peak value VCSEL 102 itself to generate a short optical pulse in this way, it is possible to realize an optical pulse with a short pulse width suitable for a LiDAR system while avoiding high costs for the driver unit and the electrical transmission unit. Specifically, it is possible to realize an optical pulse with a short pulse width of about 50 ps to 1 ns suitable for a LiDAR system. Furthermore, since an optical pulse can be generated in the long wavelength region, it is possible to increase the upper limit of the peak value of the optical pulse from the viewpoint of eye safety.

[0058] Next, an example of a method for manufacturing the light emitting device 100 according to this embodiment will be described below. First, the semiconductor layers constituting the excitation VCSEL 101 and the semiconductor layers constituting the high peak value VCSEL 102 are grown separately on the semiconductor substrate 103 and the semiconductor substrate 205, respectively, by metal organic chemical vapor deposition or molecular beam epitaxy. In this way, growth wafers for the excitation VCSEL 101 and the high peak value VCSEL 102 are prepared. As the semiconductor layers constituting the excitation VCSEL 101, the semiconductor layers constituting the lower DBR layer 104, the resonator portion 105, and the upper DBR layer 110 are grown on the semiconductor substrate 103. As the semiconductor layers constituting the high peak value VCSEL 102, the semiconductor layers constituting the upper DBR layer 204, the saturable absorbing layer 203, the carrier block layer 202, the active layer 201, and the lower DBR layer 200 are grown on the semiconductor substrate 205.

[0059] For the growth wafer for the excitation VCSEL 101, the following steps are further carried out. First, the upper DBR layer 110, the p-type layer 109, and the active layer 108 are patterned using photolithography and etching techniques such as dry etching. This forms a columnar mesa portion 114 with a diameter of about 30 μm. Note that during patterning, the resonator portion 105 around the mesa portion 114 or even the area below it may be removed by etching.

[0060] Next, thermal oxidation is performed in a water vapor atmosphere at about 450° C. to remove Al from the upper DBR layer 110. 0.98 Ga 0.02 The As layer is oxidized from the sidewall of the mesa portion 114 to form the oxidized constriction layer 112. At this time, by controlling the oxidation time, a non-oxidized portion in the center of the mesa portion 114 and an oxidized portion (oxidized constriction layer 112) in the vicinity of the sidewall of the mesa portion 114 are formed. 0.98 Ga 0.02 The oxidation time is controlled so that the diameter of the non-oxidized portion of the As layer becomes about 10 μm.

[0061] A protective film 160, which is an insulating film, is formed by using a plasma CVD method, which is an insulating film deposition method, and a lithography method, which is a pattern formation method, so as to cover the mesa side surface and the etched portion. Next, an opening is formed in a part of the protective film 160 on the upper surface of the mesa portion 114 by using photolithography and vacuum deposition, and an electrode 150, which is a p-side electrode, is formed in that part. In addition, an electrode 151, which is an n-side electrode, is formed on the surface of the semiconductor substrate 103 opposite to the mesa portion 114. The electrode 150 has a circular ring pattern, and the central opening becomes a circular window for light extraction. In this embodiment, the electrode 150 has a circular ring pattern, but the present invention is not limited to this, and the electrode 150 may be, for example, a square, a rectangle, or another polygonal shape.

[0062] Next, in order to obtain good electrical characteristics, a heat treatment is performed in a high-temperature nitrogen atmosphere to alloy the interface between the electrode material and the semiconductor material, completing the excitation VCSEL 101. Note that by forming multiple mesas 114 in the excitation VCSEL 101 as necessary, it is possible to simultaneously form multiple light emitting portions within the surface of the high peak value VCSEL 102 corresponding to the multiple mesas 114. A configuration in which multiple light emitting portions are formed will be described in the fourth embodiment.

[0063] Next, a growth wafer for the high peak value VCSEL 102 is laminated on the excitation VCSEL 101 formed as described above, with the lower DBR layer 200 on the excitation VCSEL 101 side and the semiconductor substrate 205 on the upper side. The lamination method is not particularly limited and can be selected appropriately. For example, the growth wafer for the high peak value VCSEL 102 can be laminated by bonding it to the surface of the excitation VCSEL 101 other than the portion where the excitation light 113 is emitted using an adhesive with a low absorption rate of the excitation light 113. Also, for example, gold can be evaporated on the surface of the growth wafer for the high peak value VCSEL 102 other than the portion where the excitation light 113 is incident on the lower DBR layer 104, and the gold can be joined to the gold evaporated on the upper surface of the excitation VCSEL 101 for lamination.

[0064] Next, if necessary, a thinning process is performed on the semiconductor substrate 205 before or after stacking. Finally, an AR coating 206 is formed on the surface of the semiconductor substrate 205 in the high peak value VCSEL 102. In this manner, the light emitting device 100 according to this embodiment is manufactured.

[0065] As described above, according to this embodiment, it is possible to realize a light emitting device 100 capable of generating an optical pulse with a short optical pulse width and a high peak value in the long wavelength region.

[0066] [Second embodiment] A light emitting device according to a second embodiment of the present invention will be described with reference to Figures 5 and 6. Note that the same components as those in the light emitting device according to the first embodiment are given the same reference numerals, and descriptions thereof will be omitted or simplified.

[0067] The light emitting device according to this embodiment is similar to the light emitting device according to the first embodiment except for the configuration of the high peak value VCSEL, and has an excitation VCSEL similar to that of the light emitting device according to the first embodiment. In this embodiment, the differences from the light emitting device according to the first embodiment will be mainly described, and descriptions of the parts common to the light emitting device according to the first embodiment will be omitted as appropriate.

[0068] 5 is a schematic cross-sectional view showing a high peak value VCSEL 300 in a light emitting device according to the present embodiment. The light emitting device according to the present embodiment has a high peak value VCSEL 300 instead of the high peak value VCSEL 102 in the configuration according to the first embodiment. The configuration of the light emitting device according to the present embodiment other than the high peak value VCSEL 300 is the same as the configuration according to the first embodiment.

[0069] The high peak value VCSEL 300 differs from the high peak value VCSEL 102 in that instead of the active layer 201, the high peak value VCSEL 300 has an active layer 301 in which the position of the quantum well layer is optimized in accordance with the absorption characteristics of the excitation light 113. The active layer 301, like the active layer 201, can be configured to have a quantum well structure in which five InGaAs quantum well layers, each 8 nm thick, are arranged in an InGaAsP barrier layer, and to have a thickness of 3.2 μm. On the other hand, the active layer 301 differs from the active layer 201 in that the position of the quantum well layer is optimized in accordance with the absorption characteristics of the excitation light 113, as described below. The configuration of the high peak value VCSEL 300 other than the active layer 301 is the same as that of the high peak value VCSEL 102.

[0070] Fig. 6 is a graph showing the light absorption amount, which is the proportion of excitation light 113 absorbed in active layer 301 when excitation light 113 travels a specific distance from an end in the thickness direction of active layer 301. In Fig. 6, the horizontal axis shows the position in the thickness direction of active layer 301, with the boundary with lower DBR layer 200, which is the end of active layer 301 where excitation light 113 is incident, being set at 0 µm. The vertical axis shows the integral value of the light absorption amount from 0 µm to the position on the horizontal axis.

[0071] 6, it can be seen that the slope of the graph is steep near the 0 μm position, that is, the amount of light absorption per unit length in the thickness direction of the active layer 301 is large. This means that the amount of carriers generated in the active layer 301 is large near the 0 μm position.

[0072] Therefore, in this embodiment, taking into consideration the bias in the amount of carriers generated in the active layer 301, the multiple quantum well layers are arranged in the active layer 301 at optimal positions, specifically, more of them are arranged on the side closer to the end where the excitation light 113 is incident. In this embodiment, the multiple quantum well layers in the active layer 301 are arranged at the positions indicated by the arrows in Fig. 6, and are arranged biased in the thickness direction of the active layer 301 towards the end of the active layer 301 where the excitation light 113 is incident.

[0073] More specifically, the position of the quantum well layer in the active layer 301 according to this embodiment can be set as follows. In the case of five quantum well layers, it is preferable from the viewpoint of carrier absorption to place the quantum well layers at positions where the optical absorption is 0.1, 0.3, 0.5, 0.7, and 0.9 for the optical absorption amounts shown in Fig. 6. On the other hand, by placing the quantum well layers at the antinode positions of the standing wave generated in the active layer 301, a higher optical amplification gain can be obtained.

[0074] Considering the two viewpoints of carrier absorption and optical amplification gain, five quantum well layers can be arranged at positions that are discrete positions that are antinodes of the standing wave and are close to the positions where the optical absorption amounts are 0.1, 0.3, 0.5, 0.7, and 0.9. The specific positions of the quantum well layers in the active layer 301 set in this embodiment are indicated by arrows in FIG. 6. As shown in FIG. 6, the five quantum well layers are arranged at intervals of an integer multiple of a distance of about 229 nm in the thickness direction of the active layer 301 as antinode positions of the standing wave in the active layer 301. First, two quantum well layers are arranged at a position near 229 nm, then one quantum well layer at a position near 457 nm, then one quantum well layer at a position near 914 nm, and finally one quantum well layer at a position near 1.6 μm. On the other hand, no quantum well layers are arranged between the positions of 1.6 μm and 3.2 μm in the active layer 301. The center of gravity of the five quantum well layers thus arranged is located near 686 nm, which is located closer to the end of active layer 301 where excitation light 113 is incident than the center of active layer 301 in the thickness direction.

[0075] Thus, in this embodiment, the active layer 301 has a plurality of quantum well layers arranged biased toward the end of the active layer 301 on the side where the excitation light 113 is incident. That is, the center of gravity of the plurality of quantum well layers in the active layer 301 is located toward the end of the active layer 301 on the side where the excitation light 113 is incident, rather than the center in the thickness direction of the active layer 301. This allows carriers generated in the active layer 301 to be injected into the plurality of quantum well layers more uniformly than in the first embodiment. As a result, according to this embodiment, the peak power of the high peak optical pulse emitted from the high peak VCSEL 300 can be increased more than in the first embodiment, and a light source device with excellent power conversion efficiency can be realized.

[0076] Here, as can be seen from FIG. 6, since there is little carrier generation between the 1.6 μm position and the 3.2 μm position, in this embodiment, a quantum well layer is not disposed. If the thickness of the active layer 301 is 1.6 μm, 90% of the excitation light 113 is absorbed. On the other hand, even if the thickness of the active layer 301 is doubled to 3.2 μm, the optical energy absorbed by the increased amount is less than 10%. Therefore, from the viewpoint of the amount of excitation light 113 absorbed by the active layer 301, the effect of doubling the thickness of the active layer 301 from 1.6 μm, that is, increasing the thickness to 3.2 μm is small.

[0077] The design concept of a normal optically pumped VCSEL that is not a high peak type considers only the amount of pump light absorbed in the active layer 301. For this reason, according to this design concept, the absorption rate of the pump light by the active layer when the pump light propagates from one end of the active layer to the other is kept to 90% or less, taking into account the balance with the thickness of the active layer, that is, the thickness of the active layer is often kept to 1.6 μm or less.

[0078] On the other hand, in the high peak value VCSEL 102, 300, which is an optically pumped and high peak value VCSEL, it is important that the pump light 113 does not excite the saturable absorbing layer 203 that is located beyond the active layer 201, 301. For this reason, the high peak value VCSEL 102, 300 adopts a unique design concept of absorbing the pump light 113 and not allowing it to reach the saturable absorbing layer 203, rather than a design concept only for the active layer to convert the pump light 113 into carriers and emit light again. Therefore, in the high peak value VCSEL 102, 300, it is important that the active layer 201, 301 is thicker than that of a normal optically pumped VCSEL.

[0079] In this embodiment, in addition to the above-mentioned arrangement of the quantum well layers, the multiple quantum well layers may be arranged in the active layer 301 in an arrangement that can utilize carriers more effectively than in the first embodiment. That is, in this embodiment, the multiple quantum well layers may be arranged so that the center of gravity of the multiple quantum well layers is biased toward the end side where the excitation light 113 is incident. Specifically, the multiple quantum well layers may be arranged so that the center of gravity of the multiple quantum well layers is located toward the end side where the excitation light 113 of the active layer 301 is incident from the center in the thickness direction of the active layer 301. In addition, although the case where the quantum well layer is five layers has been described in this embodiment, multiple quantum well layers other than five layers can also be arranged according to the same design concept as above.

[0080] [Third embodiment] A light emitting device according to a third embodiment of the present invention will be described with reference to Fig. 7. Note that the same components as those in the light emitting devices according to the first and second embodiments are given the same reference numerals, and descriptions thereof will be omitted or simplified.

[0081] The light emitting device according to this embodiment is similar to the light emitting device according to the first embodiment except for the configuration of the high peak value VCSEL, and has an excitation VCSEL similar to that of the light emitting device according to the first embodiment. In this embodiment, the differences from the light emitting device according to the first embodiment will be mainly described, and descriptions of the parts common to the light emitting device according to the first embodiment will be omitted as appropriate.

[0082] 7 is a schematic cross-sectional view showing a high peak value VCSEL 400 in a light emitting device according to the present embodiment. The light emitting device according to the present embodiment has a high peak value VCSEL 400 instead of the high peak value VCSEL 102 in the configuration according to the first embodiment. The configuration of the light emitting device according to the present embodiment other than the high peak value VCSEL 400 is similar to the configuration according to the first embodiment.

[0083] The high peak value VCSEL 400 has a configuration similar to that of the high peak value VCSEL 300 according to the second embodiment. The high peak value VCSEL 400 differs from the high peak value VCSEL 300 in that the high peak value VCSEL 400 has a saturable absorbing layer 403 made of a different material instead of the saturable absorbing layer 203. The configuration of the high peak value VCSEL 400 other than the saturable absorbing layer 403 is similar to that of the high peak value VCSEL 300.

[0084] The saturable absorbing layer 403 may be configured to have a plurality of quantum well layers in a barrier layer, specifically, to have a quantum well structure in which four 8 nm-thick InGaAs quantum well layers are arranged in the barrier layer, as in the first and second embodiments. Meanwhile, in this embodiment, unlike the first and second embodiments, the barrier layer may be made of InP instead of InGaAsP. The purpose of making the barrier layer of InP instead of InGaAsP is to make the band gap of the barrier layer in the saturable absorbing layer 403 larger than the energy of the excitation light 113. This increases the amount of absorption of the excitation light 113 by the barrier layer in the saturable absorbing layer 403, and as a result, the absorption of the excitation light 113 by the entire saturable absorbing layer 403 can be reduced.

[0085] Specifically, in the high peak value VCSEL 400 in which the barrier layer of the saturable absorbing layer 403 is made of InP, the absorption rate of the pump light 113 by the barrier layer of the saturable absorbing layer 403 is 10 times higher than in the first and second embodiments in which the barrier layer of the saturable absorbing layer 203 is made of InGaAsP. Therefore, in this embodiment, the absorption of the pump light 113 by the saturable absorbing layer 403 can be suppressed to 1 / 10 or less of that in the first and second embodiments.

[0086] In this embodiment, the quantum well layer in the saturable absorbing layer 403 may be made of InGaAs. Therefore, during crystal growth of the saturable absorbing layer 403, it is necessary to switch between the source materials of the group III elements and the source materials of the group V elements when growing a barrier layer made of InP and a quantum well layer made of InGaAs. In particular, the difficulty of crystal growth increases with respect to the group V elements, since the group V elements are likely to escape from the epitaxial surface at high temperatures during epitaxial growth. Therefore, from the viewpoint of facilitating crystal growth, the barrier layer of the saturable absorbing layer 403 may be made of InGaAsP, which is InP with a small amount of GaAs added.

[0087] In this manner, in this embodiment, the barrier layer of the saturable absorbing layer 403 is configured so that the band gap of the barrier layer of the saturable absorbing layer 403 is larger than or equal to the energy of the excitation light 113. As long as the material satisfies this band gap, the material constituting the barrier layer is not limited to InP, and materials other than InP can be used as the material constituting the barrier layer.

[0088] In this embodiment, the high peak value VCSEL 300 according to the second embodiment is provided with the saturable absorbing layer 403 instead of the saturable absorbing layer 203, but the present invention is not limited to this. In the high peak value VCSEL 102 according to the first embodiment, the saturable absorbing layer 203 may be replaced by the saturable absorbing layer 403 similar to that of this embodiment.

[0089] [Fourth embodiment] A light emitting device according to a fourth embodiment of the present invention will be described with reference to Fig. 8. Note that the same components as those in the light emitting devices according to the first to third embodiments are given the same reference numerals, and the description will be omitted or simplified.

[0090] The light emitting devices according to the first to third embodiments can be configured as a so-called VCSEL array having a plurality of light emitting portions in the high peak value VCSEL 102 by providing a plurality of mesa portions in the excitation VCSEL 101. In this embodiment, a case where the light emitting device according to the first embodiment is configured as a VCSEL array will be described.

[0091] 8 is a schematic cross-sectional view showing a light emitting device 500 according to the present embodiment. In the light emitting device 500 according to the present embodiment, a plurality of mesa portions 114 are provided in the excitation VCSEL 101. In the excitation VCSEL 101, the plurality of mesa portions 114 may be arranged in a two-dimensional array, may be disposed in a linear or curved shape, or may be arranged along a predetermined two-dimensional shape.

[0092] The electrodes 150 provided on each of the multiple mesa portions 114 are electrically connected to a common electrode (not shown). A current for driving the excitation VCSEL 101 is injected into the excitation VCSEL 101 from an external circuit, which is a driving portion, via the common electrode connected to the multiple electrodes 150 and the electrode 151.

[0093] In the high peak-value VCSEL 102, each of the portions corresponding to the multiple mesas 114 provided in the excitation VCSEL 101 serves as a light-emitting portion 505. In this manner, each of the multiple light-emitting portions 505 present in the high peak-value VCSEL 102 corresponding to the multiple mesas 114 is excited by the excitation light 113 from the mesa portion 114 in the same manner as in the first embodiment, and can emit a high peak-value, short-pulse optical pulse.

[0094] In the above, a case has been described in which a VCSEL array is constructed using the light emitting device according to the first embodiment, but a VCSEL array can also be constructed using the light emitting devices according to the second and third embodiments in a similar manner to the above.

[0095] In this manner, according to this embodiment, it is possible to realize a VCSEL array using the light emitting devices according to the first to third embodiments. Note that, in this embodiment, an example in which the electrode 150 is electrically connected to a common electrode has been shown, but the present invention is not limited to this, and each light emitting portion 505 can be driven independently by connecting the electrode 150 to separate electrodes.

[0096] [Fifth embodiment] A distance measuring device according to a fifth embodiment of the present invention will be described with reference to Fig. 9. Fig. 9 is a block diagram showing a schematic configuration of the distance measuring device according to this embodiment.

[0097] The distance measuring device 1000 according to this embodiment is a distance measuring device (LiDAR device) in which the light emitting device 500 according to the fourth embodiment is applied to a light source unit. The distance measuring device 1000 may be configured with a control unit 1010, a surface emitting laser array driver 1020, a surface emitting laser array 1030, an emission side optical system 1040, a light receiving side optical system 1060, an image sensor 1070, and a distance data processing unit 1080.

[0098] The surface-emitting laser array 1030 is a light-emitting device 500 according to the fourth embodiment mounted in a package. The surface-emitting laser array driver 1020 is a driver that receives a drive signal from the control unit 1010, generates a drive current for oscillating the surface-emitting laser array 1030, and outputs the drive current to the surface-emitting laser array 1030. The drive current output to the surface-emitting laser array 1030 is injected into the excitation VCSEL 101 in the light-emitting device 500 via a plurality of electrodes 150 and an electrode 151. The surface-emitting laser array 1030 and the surface-emitting laser array driver 1020 may be one light-emitting device.

[0099] The light-emitting optical system 1040 is an optical system that emits laser light generated by the surface-emitting laser array 1030 toward a distance measurement target range. The light-receiving optical system 1060 is an optical system that guides laser light reflected by the measurement target 1200 to an image sensor 1070. Note that, although the light-emitting optical system 1040 and the light-receiving optical system 1060 are represented by a single convex lens-shaped member in Fig. 9, they are not composed of only a single convex lens-shaped member, but are composed of a lens group combining a plurality of lenses.

[0100] The image sensor 1070 is a photoelectric conversion device in which a plurality of pixels including a photoelectric conversion unit are arranged in a two-dimensional array, and is a light receiving device that outputs an electrical signal according to incident light. The image sensor 1070 may be, for example, an image sensor in which optical sensors are arranged in a two-dimensional array. The optical sensor may be, for example, a SPAD (Single Photon Avalanche Diode) using SiGe or InGaAs in the light receiving unit capable of detecting the SWIR band. A CMOS circuit is electrically connected to this image sensor unit, for example, as a reading unit. The distance data processing unit 1080 has a function as a distance information acquisition unit that generates and outputs information regarding the distance to the measurement target object 1200 present in the distance measurement target range based on a signal from the image sensor 1070. Note that the distance data processing unit 1080 may be electrically connected to the image sensor 1070, and may be disposed in the same package as the image sensor 1070, or may be disposed in a package separate from the image sensor 1070.

[0101] The control unit 1010 is configured with an information processing device including a microcomputer and a logic circuit, and functions as a central processing device that governs the operation of the distance measuring device 1000, such as controlling the operation of each unit and performing various calculation processes.

[0102] As described above, a light emitting device suitable for a LiDAR system is preferably a light emitting device capable of generating an optical pulse with a short optical pulse width and a high peak value. Specifically, the optical pulse width of a light source suitable for a LiDAR system is, for example, in the range of about 50 ps to 1 ns. On the other hand, from the electrical viewpoint of driving a VCSEL and a VCSEL, it is not easy to emit light with such a short pulse width. Since a VCSEL emits light according to the amount of current injected, in order to make the optical pulse about 50 ps to 1 ns, it is necessary to make the current pulse driving the VCSEL about the same. In other words, from the driver unit to the VCSEL, it is necessary to have excellent electrical characteristics in the high frequency band such as 1 GHz or 10 GHz as a frequency component and to handle a current exceeding 1 A. Doing so has the problem of being expensive compared to the case where an electrical transmission unit to the driver and VCSEL is configured only with an electrical circuit that handles only the frequency band below that.

[0103] Therefore, in this embodiment, the light emitting device according to the fourth embodiment, which is a VCSEL array formed by using the light emitting devices according to the first to third embodiments, is used as a light source unit, so that the VCSEL itself generates a short pulse. This avoids high costs for the driver unit and the electrical transmission unit, and realizes an optical pulse of about 50 ps to 1 ns, which is preferable for a LiDAR system.

[0104] Next, the operation of the distance measuring device 1000 according to this embodiment will be described with reference to FIG. First, the control unit 1010 outputs a drive signal to the surface-emitting laser array driver 1020. The surface-emitting laser array driver 1020 receives the drive signal from the control unit 1010 and injects a current of a predetermined current value into the surface-emitting laser array 1030. This causes the surface-emitting laser array 1030 to oscillate, and laser light is output from the surface-emitting laser array 1030. At this time, the pulse width of the light emitted from the surface-emitting laser array 1030 is narrower than the pulse width of the injected current, as described above.

[0105] The laser light generated by the surface-emitting laser array 1030 is emitted toward the distance measurement range by the light-emitting side optical system 1040. Of the laser light irradiated to the measurement object 1200 in the distance measurement range, the laser light reflected by the measurement object 1200 and incident on the light-receiving side optical system 1060 is guided to the image sensor 1070 by the light-receiving side optical system 1060.

[0106] Each pixel of the image sensor 1070 generates an electrical signal pulse in accordance with the timing at which the laser light is incident. The electrical signal pulse generated by the image sensor 1070 is input to the distance data processing unit 1080.

[0107] The distance data processing unit 1080 generates information about the distance to the measurement object 1200 along the light propagation direction based on the reception timing of the electrical signal pulse output from the image sensor 1070. By calculating the distance information based on the electrical signal pulse output from each pixel of the image sensor 1070, three-dimensional information of the measurement object 1200 can be acquired.

[0108] The distance measuring device 1000 according to the present embodiment can be applied to, for example, a control device in the field of automobiles for controlling a vehicle to avoid collision with another vehicle, or a control device for controlling automatic driving by following another vehicle. The distance measuring device 1000 according to the present embodiment can also be applied to other moving bodies (moving devices) such as ships, aircraft, and industrial robots, and moving body detection systems. The distance measuring device 1000 according to the present embodiment can be widely applied to equipment that uses information of objects recognized three-dimensionally, including distance information. These moving bodies can be configured to include the distance measuring device according to the present embodiment and a control means for controlling the moving body based on information on the distance acquired by the distance measuring device.

[0109] In addition, the three-dimensional information including the depth that can be acquired by the distance measuring device 1000 according to this embodiment can be used in an image capturing device, an image processing device, a display device, etc. For example, it is possible to use the three-dimensional information acquired by the distance measuring device 1000 according to this embodiment to display a virtual object on an image of the real world without creating a sense of incongruity. In addition, by storing the three-dimensional information together with the image information, it is also possible to correct the blur of the captured image after shooting.

[0110] As described above, according to this embodiment, it is possible to realize a high-performance distance measuring device equipped with a light emitting device capable of generating an optical pulse with a short optical pulse width and a high peak value.

[0111] [Sixth embodiment] A distance measuring device according to a sixth embodiment of the present invention will be described with reference to Figs. 10 and 11. Fig. 10 is a block diagram showing a schematic configuration of the distance measuring device according to this embodiment. Fig. 11 is a schematic cross-sectional view showing a configuration example of a surface emitting laser array in the distance measuring device according to this embodiment. Components similar to those in the light emitting devices according to the first to fourth embodiments and the distance measuring device according to the fifth embodiment are given the same reference numerals, and descriptions thereof will be omitted or simplified.

[0112] 10, the distance measuring device 1001 according to this embodiment differs from the distance measuring device 1000 according to the fifth embodiment in that the surface emitting laser array 1030 further includes an emission timing monitor unit 1031. Other points of the distance measuring device 1001 according to this embodiment are similar to those of the distance measuring device 1000 according to the fifth embodiment.

[0113] The surface emitting laser array 1030 includes a light emitting device 500, an emission timing monitor unit 1031, a base 1032, and a window material 1033, as shown in FIG. 11. The base 1032 is a part of a package that mounts the light emitting device 500 and the emission timing monitor unit 1031, and has a recess that accommodates the light emitting device 500 and the emission timing monitor unit 1031. The base 1032 may be made of, for example, ceramic. The window material 1033 is fixed to the base 1032 so as to cover the recess of the base 1032 on which the light emitting device 500 and the emission timing monitor unit 1031 are mounted. The light emitting device 500 is the light emitting device 500 according to the fourth embodiment. The light emitting timing monitor unit 1031 is made of a semiconductor substrate having, for example, a square shape of 0.3 mm square, and has a photodiode with a diameter of a light receiving area of, for example, 100 μm as a light receiving element.

[0114] A common electrode and an electrode 151 to which the electrode 150 of the light emitting device 500 is connected, and an anode and a cathode of a photodiode constituting the light emission timing monitor unit 1031 are electrically connected to electrodes (not shown) provided on the outer periphery of a base 1032. A pulse current supplied from the surface emitting laser array driver 1020 is supplied to the light emitting device 500 via the electrodes provided on the base 1032. In addition, an electric signal generated by the light emission timing monitor unit 1031 is supplied to the distance data processing unit 1080 via the electrodes provided on the base 1032.

[0115] Next, the operation of the distance measuring device 1001 according to this embodiment will be described with reference to FIGS. First, the control unit 1010 outputs a drive signal to the surface-emitting laser array driver 1020. The surface-emitting laser array driver 1020 receives the drive signal from the control unit 1010 and injects a current of a predetermined current value into the light-emitting device 500 of the surface-emitting laser array 1030. This causes the light-emitting device 500 to oscillate, and laser light is output from the light-emitting device 500. At this time, the pulse width of the light emitted from the light-emitting device 500 is narrower than the pulse width of the injected current, as described above.

[0116] The laser light generated by the light emitting device 500 is emitted from the surface emitting laser array 1030 through the window material 1033, and is emitted toward the distance measurement target range by the light emitting side optical system 1040. At this time, although the window material 1033 is subjected to an AR coating, a part of the light is reflected by the window material 1033 and enters the light emission timing monitor unit 1031.

[0117] The light emission timing monitor unit 1031 receives the incident light with a photodiode, converts it into an electrical signal, and outputs it to the distance data processor 1080. The distance data processor 1080 generates information about the distance to the measurement object 1200 along the light propagation direction based on the time difference between the reception timing of the electrical signal pulse from the image sensor 1070 and the reception timing of the electrical signal from the light emission timing monitor unit 1031. Then, the distance data processor 1080 calculates distance information based on the electrical signal pulse output from each pixel of the image sensor 1070, thereby acquiring three-dimensional information of the measurement object 1200.

[0118] In this manner, in the distance measuring device 1001 of this embodiment, the light emission timing of the surface-emitting laser array 1030 is detected by the light emission timing monitor unit 1031. Then, distance information is calculated using the light emission timing detected by the light emission timing monitor unit 1031. Therefore, even if the light emission timing of the surface-emitting laser array 1030 is shifted due to factors such as the environmental temperature, the distance measuring accuracy of the distance measuring device 1001 is not affected, and high distance measuring accuracy can be maintained.

[0119] As described above, according to this embodiment, in the distance measuring device 1001 using an optical pulse with a high peak value and a short pulse, it is possible to reduce the effect of changes in the environmental temperature on distance measurement accuracy.

[0120] [Seventh embodiment] A moving body according to the seventh embodiment of the present invention will be described with reference to Fig. 12. Fig. 12 is a diagram showing an example of the configuration of a moving body according to this embodiment.

[0121] 12(a) shows an example of the configuration of a device 2000 mounted on a vehicle. The device 2000 has a distance measurement unit 2001 and a collision determination unit 2002. The distance measurement unit 2001 is configured by the distance measurement device 1000 according to the fifth embodiment or the distance measurement device 1001 according to the sixth embodiment, and measures the distance to an object and acquires information on the distance to the object. The collision determination unit 2002 determines whether or not there is a possibility of a collision based on the distance measured by the distance measurement unit 2001.

[0122] The device 2000 is connected to a vehicle information acquisition device 2010 and can acquire vehicle information such as vehicle speed, yaw rate, and steering angle. In addition, the device 2000 is connected to a control ECU 2020, which is a control device that outputs a control signal to generate a braking force for the vehicle based on the judgment result of the collision judgment unit 2002. In addition, the device 2000 is also connected to an alarm device 2030 that issues an alarm to the driver based on the judgment result of the collision judgment unit 2002. For example, when the judgment result of the collision judgment unit 2002 indicates that there is a high possibility of a collision, the control ECU 2020 instructs the vehicle to apply the brakes, stop the accelerator, suppress the engine output, etc., to avoid the collision and reduce damage. The alarm device 2030 warns the user through alarm output such as sound, display of alarm information on the screen of a car navigation system, etc., and vibration of the seat belt and steering wheel. These devices of the device 2000 function as a mobile object control unit that controls the operation of controlling the vehicle as described above.

[0123] In this embodiment, the device 2000 measures distances around the vehicle, for example, in front or behind. Fig. 12(b) shows the device 2000 when measuring distances in front of the vehicle (distance measurement range 2040). A vehicle information acquisition device 2010, which serves as a distance measurement control means, sends an instruction to the device 2000 or the distance measurement unit 2001 to perform a distance measurement operation. With this configuration, the accuracy of distance measurement can be further improved.

[0124] Although the above describes the control of avoiding collision with other vehicles, the present embodiment can also be applied to control of automatic driving by following other vehicles, control of automatic driving so as not to deviate from lanes, etc. Furthermore, the device is not limited to vehicles such as automobiles, but can be applied to moving bodies (moving devices) such as ships, aircraft, artificial satellites, industrial robots, and consumer robots. In addition, the present embodiment can be applied to devices that use object recognition or biometric recognition, such as intelligent transport systems (ITS) and surveillance systems, in addition to moving bodies.

[0125] [Modified embodiment] The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, an example in which part of the configuration of any one of the embodiments is added to another embodiment, or an example in which part of the configuration of another embodiment is substituted therefor, is also an embodiment of the present invention.

[0126] In the above embodiment, a mesa-type VCSEL with an oscillation wavelength of 940 nm is used as the excitation VCSEL 101, and a VCSEL with an oscillation wavelength of 1550 nm is used as the high peak VCSEL 102, but the present invention is not limited to this. The present invention can be applied to other configuration examples based on the same concept.

[0127] For example, a VCSEL is preferable as an excitation light source that emits excitation light toward the high peak value VCSEL 102, but it is sufficient if the excitation light can be emitted toward the high peak value VCSEL 102. Specifically, instead of the excitation VCSEL 101, other types of excitation light sources such as a photonic crystal laser and an edge-emitting laser can be used. The semiconductor light-emitting element as the excitation light source may have an active layer that generates light by injecting a current and a resonator section that oscillates the light generated in the active layer. For example, in a photonic crystal laser, the photonic crystal itself functions as a reflecting mirror, and in an edge-emitting laser, the cleavage surface functions as a reflecting mirror. In addition, the semiconductor light-emitting element such as the excitation VCSEL 101 used as the excitation light source does not necessarily have to have a mesa structure, and may have a region into which a current is injected defined by patterning a transparent electrode such as the electrode 150, for example. The wavelength of the excitation light emitted by the excitation light source such as the excitation VCSEL 101 is not limited to the above-mentioned wavelengths, but may be shorter than the oscillation wavelength of the high peak value VCSEL 102. The oscillation wavelength of the high peak value VCSEL 102 is not limited to the above-mentioned wavelengths, but may be longer than the wavelength of the excitation light.

[0128] In the above embodiment, the material system of the pumping VCSEL 101 is GaAs-based, and the material system of the high peak value VCSEL 102 is InP-based, but the present invention is not limited to these. For the material system of the pumping VCSEL 101 and the material system of the high peak value VCSEL 102, other material systems such as GaN-based materials may be used as appropriate.

[0129] Furthermore, the DBR layers in the pump VCSEL 101 and the high peak VCSEL 102 according to the above embodiment do not necessarily need to be made of the above-mentioned materials, and may be made of materials other than these. In this case, too, by configuring the DBR layers to have the same functions as the above embodiment, the same effects as the present embodiment can be achieved.

[0130] It should be noted that the above-mentioned embodiments are merely examples of the implementation of the present invention, and the technical scope of the present invention should not be interpreted as being limited by these embodiments. In other words, the present invention can be implemented in various forms without departing from its technical concept or main features.

[0131] The disclosure of this embodiment includes the following configuration. (Configuration 1) a first semiconductor light emitting element having a first active layer and a first resonator portion on a semiconductor substrate and emitting a first light; a second semiconductor light emitting element that emits a second light and that has a first reflecting mirror, a second resonator unit including a second active layer excited by the first light, and a second reflecting mirror stacked in this order on the first semiconductor light emitting element; a driving unit that injects a current into the first semiconductor light emitting element, an oscillation wavelength of the second semiconductor light emitting element is longer than an oscillation wavelength of the first semiconductor light emitting element; the second semiconductor light emitting element includes a saturable absorbing layer between the second resonator portion and the second reflector, A light emitting device, characterized in that the thickness L of the second active layer and the absorption coefficient α of the second active layer satisfy the following formula (1). 3.45≦α×L≦15 …(1) (Configuration 2) The first semiconductor light emitting element has a third reflector, the first resonator portion including the first active layer, and a fourth reflector laminated in this order on the semiconductor substrate. 2. The light emitting device according to configuration 1. (Configuration 3) A carrier block layer is provided between the second resonator portion and the saturable absorbing layer. 3. The light emitting device according to configuration 1 or 2. (Configuration 4) The second active layer has a thickness such that the absorption amount of the first light is 90% or more. 4. The light emitting device according to any one of configurations 1 to 3. (Configuration 5) The thickness L and the absorption coefficient α satisfy the following formula (2): 5. The light emitting device according to any one of configurations 1 to 4. 4.2≦α×L≦7.5 …(2) (Configuration 6) The thickness L satisfies the following formula (3). 5. The light emitting device according to any one of configurations 1 to 4. 2.3 μm ≦ L ≦ 10 μm … (3) (Configuration 7) The thickness L satisfies the following formula (4). 5. The light emitting device according to any one of configurations 1 to 4. 2.8μm≦L≦5μm …(4) (Configuration 8) The second semiconductor light emitting element is configured to emit the second light having a profile that has a maximum peak value and converges to a stable value that is a predetermined light intensity after the maximum peak value. 7. The light emitting device according to any one of configurations 1 to 6, (Configuration 9) The second active layer includes a plurality of quantum well layers. 9. The light emitting device according to any one of configurations 1 to 8. (Configuration 10) The plurality of quantum well layers are located at antinodes of a standing wave generated in the second active layer. 10. The light emitting device according to configuration 9. (Configuration 11) The center of gravity of the plurality of quantum well layers is located at the center in the thickness direction of the second active layer. 11. The light emitting device according to configuration 9 or 10. (Configuration 12) The center of gravity of the plurality of quantum well layers is located closer to the end of the second active layer on which the first light is incident than the center in the thickness direction of the second active layer. 11. The light emitting device according to configuration 9 or 10. (Configuration 13) the saturable absorbing layer includes a barrier layer and a quantum well layer provided in the barrier layer; The band gap of the barrier layer is equal to or greater than the energy of the first light. 13. The light emitting device according to any one of configurations 1 to 12. (Configuration 14) The barrier layer is made of InP or InGaAsP. 14. The light emitting device according to claim 13. (Configuration 15) the second active layer has a barrier layer and a quantum well layer provided in the barrier layer; the barrier layer is made of InGaAsP; The quantum well layer is made of InGaAs. 15. The light emitting device according to any one of configurations 1 to 14. (Configuration 16) The first semiconductor light emitting element has a plurality of first light emitting portions that emit the first light. 16. The light emitting device according to any one of configurations 1 to 15. (Configuration 17) The first light emitting section includes the first active layer having a mesa shape. 17. The light emitting device according to claim 16, (Configuration 18) The plurality of first light emitting units are arranged in a two-dimensional array. 18. The light emitting device according to claim 16 or 17. (Configuration 19) The second semiconductor light emitting element has a plurality of second light emitting portions that emit the second light in correspondence with the plurality of first light emitting portions. 19. The light emitting device according to any one of configurations 16 to 18. (Configuration 20) The second light emitting element further includes a light receiving element for receiving the second light emitted from the second semiconductor light emitting element. 20. The light emitting device according to any one of configurations 1 to 19. (Configuration 21) A light emitting device according to any one of configurations 1 to 20, a light receiving device that receives light emitted from the light emitting device and reflected by a measurement object; a distance information acquiring unit that acquires information about a distance to the object to be measured based on a time difference between a timing at which light is emitted from the light emitting device and a timing at which the light receiving device receives the light; A distance measuring device comprising: (Configuration 22) A mobile object, A distance measuring device according to aspect 21, a control means for controlling the moving object based on information regarding the distance acquired by the distance measuring device; A moving object comprising: [Explanation of symbols]

[0132] 100...Light emitting device 101...Excitation VCSEL 102…High peak value type VCSEL 103...Semiconductor substrate 104…Lower DBR layer 105...Resonator section 107...n-type layer 108...Active layer 109...p-type layer 110...Top DBR layer 111...Quantum well 112…Oxidized constriction layer 113…Excitation light 114…Mesa section 150...electrode 151...Electrode 160...Protective film 200…Lower DBR layer 201…Active layer 202…Carrier block layer 203...Saturable absorbing layer 204...Top DBR layer 205...Semiconductor substrate 206…AR Coat 300…High peak value type VCSEL 301…Active layer 400…High peak value type VCSEL 403...Saturable absorbing layer 500…Light emitting device 501…Light emitting part 1000, 1001...Distance measuring device

Claims

1. a first semiconductor light emitting element having a first active layer and a first resonator portion on a semiconductor substrate and emitting a first light; a second semiconductor light emitting element having a first reflecting mirror, a second resonator portion including a second active layer excited by the first light, and a second reflecting mirror stacked in this order on the first semiconductor light emitting element, and emitting a second light; a driving unit that injects a current into the first semiconductor light emitting element, an oscillation wavelength of the second semiconductor light emitting element is longer than an oscillation wavelength of the first semiconductor light emitting element; the second semiconductor light emitting element includes a saturable absorbing layer between the second resonator portion and the second reflecting mirror, A light emitting device, characterized in that a thickness L of the second active layer and an absorption coefficient α of the second active layer satisfy the following formula (1): 3.45≦α×L≦15 ... (1)

2. The first semiconductor light emitting element has a third reflector, the first resonator portion including the first active layer, and a fourth reflector laminated in this order on the semiconductor substrate.

2. The light emitting device according to claim 1 .

3. A carrier block layer is provided between the second resonator portion and the saturable absorbing layer.

3. The light emitting device according to claim 1 or 2.

4. The second active layer has a thickness such that the absorption amount of the first light is 90% or more.

3. The light emitting device according to claim 1 or 2.

5. The thickness L and the absorption coefficient α satisfy the following formula (2):

3. The light emitting device according to claim 1 or 2. 4.2≦α×L≦7.5 … (2)

6. The thickness L satisfies the following formula (3).

3. The light emitting device according to claim 1 or 2. 2.3 μm≦L≦10 μm ... (3)

7. The thickness L satisfies the following formula (4).

3. The light emitting device according to claim 1 or 2. 2.8 μm≦L≦5 μm ... (4)

8. The second semiconductor light emitting element is configured to emit the second light having a profile that has a maximum peak value and converges to a stable value that is a predetermined light intensity after the maximum peak value.

3. The light emitting device according to claim 1 or 2.

9. The second active layer includes a plurality of quantum well layers.

3. The light emitting device according to claim 1 or 2.

10. The plurality of quantum well layers are located at antinodes of a standing wave generated in the second active layer.

10. The light emitting device according to claim 9.

11. The center of gravity of the plurality of quantum well layers is located at the center in the thickness direction of the second active layer.

10. The light emitting device according to claim 9.

12. The center of gravity of the plurality of quantum well layers is located closer to the end of the second active layer on which the first light is incident than the center in the thickness direction of the second active layer.

10. The light emitting device according to claim 9.

13. the saturable absorbing layer includes a barrier layer and a quantum well layer provided in the barrier layer; The band gap of the barrier layer is equal to or greater than the energy of the first light.

3. The light emitting device according to claim 1 or 2.

14. The barrier layer is made of InP or InGaAsP.

14. The light emitting device according to claim 13.

15. the second active layer has a barrier layer and a quantum well layer provided in the barrier layer; the barrier layer is made of InGaAsP; The quantum well layer is made of InGaAs.

3. The light emitting device according to claim 1 or 2.

16. The first semiconductor light emitting element has a plurality of first light emitting portions that emit the first light.

3. The light emitting device according to claim 1 or 2.

17. The first light emitting section includes the first active layer having a mesa shape.

17. The light emitting device according to claim 16.

18. The plurality of first light emitting units are arranged in a two-dimensional array.

17. The light emitting device according to claim 16.

19. The second semiconductor light emitting element has a plurality of second light emitting portions that emit the second light in correspondence with the plurality of first light emitting portions.

17. The light emitting device according to claim 16.

20. The second light emitting element further includes a light receiving element for receiving the second light emitted from the second semiconductor light emitting element.

3. The light emitting device according to claim 1 or 2.

21. A light emitting device according to claim 1 or 2; a light receiving device that receives light emitted from the light emitting device and reflected by a measurement object; a distance information acquiring unit that acquires information about a distance to the object to be measured based on a time difference between a timing at which light is emitted from the light emitting device and a timing at which the light receiving device receives the light; A distance measuring device comprising:

22. A mobile object, A distance measuring device according to claim 21; a control means for controlling the moving object based on information regarding the distance acquired by the distance measuring device; A moving object comprising:

Images