Light source device and distance measuring device

Abstract

To provide a light source device capable of improving detection accuracy of an oscillation timing of a laser beam without reducing the light intensity of the laser beam.SOLUTION: The light source device has a light-emitting element, a light-receiving element, and a determining unit. The light-emitting element has a first reflecting mirror, a second reflecting mirror, and a resonator spacer part provided between the first reflecting mirror and the second reflecting mirror and including an active layer. The light-emitting element emits first light, which is laser light, and second light, which is spontaneous emission light. The light-receiving element detects a light quantity of the second light. The determining unit detects a timing when the first light has oscillated on the basis of the reduction in the light quantity of the second light detected by the light-receiving element.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a light source device and a distance measuring device. [Background technology]

[0002] VCSELs (Vertical Cavity Surface Emitting Lasers) have been attracting attention as light sources for ToF (Time of Flight) LiDAR (Light Detection and Ranging). VCSELs have the advantage of having little wavelength dependency on temperature.

[0003] One requirement for a light source to perform high-precision distance measurement in the above system is that it must be able to emit high-intensity short-pulse light. Patent Documents 1 and 2 disclose a VCSEL, which accumulates carriers in an active layer and emits laser light all at once, as a light source capable of emitting high-intensity short-pulse light. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2020-524910 [Patent Document 2] US Patent Application Publication No. 2014 / 0169397 Summary of the Invention [Problem to be solved by the invention]

[0005] However, with the VCSELs described in Patent Documents 1 and 2, the timing of laser oscillation fluctuates due to changes in the operating environment and physical properties, which can reduce distance measurement accuracy. While it is possible to determine the timing of laser oscillation using part of the generated laser light, there is a concern that the maximum measurable distance will be shortened because the amount of laser light irradiated on the object to be measured will be reduced.

[0006] An object of the present invention is to provide a light source device that can improve the detection accuracy of the oscillation timing of laser light without reducing the light intensity of the laser light. [Means for solving the problem]

[0007] According to one disclosure of the present specification, there is provided a laser diode having a first reflecting mirror, a second reflecting mirror, and a cavity spacer portion including an active layer provided between the first reflecting mirror and the second reflecting mirror, the laser diode having a light emitting element that emits a first light that is a laser beam and a second light that is a spontaneous emission light, a light receiving element that detects the amount of the second light, and a light receiving element that detects the amount of the second light detected by the light receiving element. rises from the start of current injection into the light emitting element until a certain time has elapsed, and then Decline To do and a determination unit that detects the timing at which the first light is oscillated. [Effects of the Invention]

[0008] According to the present invention, it is possible to realize a light source device that can improve the measurement accuracy of the oscillation timing of a laser beam without reducing the light intensity of the laser beam. Furthermore, by using such a light source device, it is possible to realize a high-performance distance measuring device with high distance measurement accuracy. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram showing an example of the configuration of a light source device according to a first embodiment of the present invention. [Figure 2] 10 is a graph showing an optical output waveform of a light emitting device according to a comparative example. [Figure 3] 4 is a graph showing an optical output waveform of the light emitting device according to the first embodiment of the present invention. [Figure 4] 4 is a graph showing temporal changes in density of carriers accumulated in the active layer of the light emitting device according to the first embodiment of the present invention and light intensity. [Figure 5] 10 is a graph showing a change in carrier density differential value over time. [Figure 6] 10 is a graph showing changes over time in light intensity and second derivatives of carrier density. [Figure 7] FIG. 5 is a schematic diagram showing an example of the configuration of a light source device according to a second embodiment of the present invention. [Figure 8] 10 is a top view showing the positional relationship between a light emitting element and a light receiving element of a light source device according to a second embodiment of the present invention. FIG. [Figure 9] 10 is a graph showing the relationship between the output and dark current of a light receiving element and the distance between a light emitting element and a light receiving element. [Figure 10] FIG. 10 is a top view (part 1) showing an example of the configuration of a light source device according to a modified example of the second embodiment of the present invention. [Figure 11] FIG. 10 is a top view (part 2) showing an example of the configuration of a light source device according to a modified example of the second embodiment of the present invention. [Figure 12] FIG. 10 is a schematic diagram showing an example of the configuration of a light source device according to a third embodiment of the present invention. [Figure 13] FIG. 10 is a top view showing an example of the configuration of a light source device according to a third embodiment of the present invention. [Figure 14] FIG. 10 is a schematic diagram showing an example of the configuration of a light source device according to a fourth embodiment of the present invention. [Figure 15] 10 is a graph showing the relationship between the output of a light receiving element and the distance between a light emitting element and a light receiving element. [Figure 16] 1 is a graph (part 1) showing the gain spectrum and the spontaneous emission spectrum of a light-emitting device. [Figure 17] 10 is a graph (part 2) showing the gain spectrum and the spontaneous emission spectrum of the light-emitting device. [Figure 18] FIG. 10 is a schematic diagram showing an example of the configuration of a light source device according to a fifth embodiment of the present invention. [Figure 19] 10 is a graph showing temporal changes in density of carriers accumulated in an active layer and light intensity of a light emitting device according to a comparative example. [Figure 20] FIG. 10 is a schematic diagram showing an example of the configuration of a light source device according to a sixth embodiment of the present invention. [Figure 21] FIG. 13 is a schematic diagram (part 1) showing an example of the configuration of a light source device according to a seventh embodiment of the present invention. [Figure 22] FIG. 20 is a schematic diagram (part 2) showing an example of the configuration of a light source device according to a seventh embodiment of the present invention. [Figure 23] FIG. 13 is a block diagram showing a schematic configuration of a distance measuring device according to an eighth embodiment of the present invention. [Figure 24] 10 is a graph showing changes in the optical waveform due to changes in the environmental temperature and changes in physical parameters over time in a semiconductor light emitting element of a comparative example. [Figure 25] 1 is a graph showing changes in optical waveform due to changes in environmental temperature and changes in physical parameters over time in a semiconductor light emitting element of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] [First embodiment] A light source device according to a first embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a schematic diagram showing an example of the configuration of a light source device according to this embodiment.

[0011] 1, the light source device 100 according to this embodiment includes a light emitting unit 110, a light emission timing monitor unit 120, and a determination unit 130. Although the light emitting unit 110, the light emission timing monitor unit 120, and the determination unit 130 are depicted in FIG. 1 as if they were separate components, any two or all of these may be configured as a single component.

[0012] The light-emitting unit 110 may be configured to include a semiconductor light-emitting element, specifically, a vertical-cavity surface-emitting laser (VCSEL) having a distributed Bragg reflector (DBR). Fig. 1 shows a schematic cross-sectional view of a light-emitting element 112 that constitutes the light-emitting unit 110.

[0013] The light-emitting element 112 includes a semiconductor substrate 10, a lower DBR layer 12, a resonator portion 14, an upper DBR layer 24, and electrodes 72 and 74. The resonator portion 14 includes a semiconductor layer 16 of a first conductivity type (e.g., n-type), an undoped spacer portion 18, and a semiconductor layer 22 of a second conductivity type (e.g., p-type). The lower DBR layer 12, the semiconductor layer 16, the undoped spacer portion 18, the semiconductor layer 22, and the upper DBR layer 24 are stacked in this order on one surface of the semiconductor substrate 10 (the upper side in FIG. 1 ). An active layer 20 is provided in the undoped spacer portion 18. An oxide constriction layer 26 is provided in the upper DBR layer 24. The layer (resonator portion 14) located between the lower DBR layer 12 and the upper DBR layer 24 is the resonator spacer portion.

[0014] The undoped spacer portion 18, the semiconductor layer 22, and the upper DBR layer 24 are processed into a mesa shape. An electrode 72 that forms an ohmic contact with the semiconductor layer 16 is provided on the semiconductor layer 16 that is exposed by processing the undoped spacer portion 18, the semiconductor layer 22, and the upper DBR layer 24 into a mesa shape. An electrode 74 that forms an ohmic contact with the upper DBR layer 24 is provided on the upper DBR layer 24. A protective film (not shown) may be provided on the sidewalls of the mesa to prevent deterioration of the semiconductor surface.

[0015] The semiconductor substrate 10 may be, for example, a GaAs substrate. The lower DBR layer 12 may be, for example, an Al 0.1 GaAs layer and Al 0.9 The lower DBR layer 12 may be configured by laminating 35 pairs of layers, each layer being a stack of a GaAs layer, where λc is the center wavelength of the high reflection band of the lower DBR layer 12, which is 940 nm in this embodiment.

[0016] The resonator section 14 is made up of a pin junction that is also present in a typical VCSEL, and has a configuration similar to a resonator section that includes an active layer within an i-layer. That is, the resonator section 14 is made up of a pin junction made up of a first conductivity type semiconductor layer 16, an undoped spacer section 18, and a second conductivity type semiconductor layer 22. The optical thickness of the resonator section 14 can be, for example, 2λc.

[0017] The active layer 20 disposed in the undoped spacer portion 18 may be composed of a multiple quantum well structure including four quantum well layers, each of which has an 8-nm-thick InGaAs well layer sandwiched between 10-nm-thick AlGaAs barrier layers. The AlGaAs barrier layers have a smaller bandgap than the barrier layers used in typical VCSEL quantum well layers, and are designed to allow carrier accumulation in the barrier layers as well. The semiconductor layer 16 may be composed of an n-type GaAs layer, the semiconductor layer 22 may be composed of a p-type GaAs layer, and the remaining portions of the undoped spacer portion 18 may be composed of undoped GaAs layers.

[0018] The active layer 20 is preferably positioned at a location offset from the antinode of the standing wave, rather than at the antinode of the standing wave as is the case with typical VCSEL designs. For example, the active layer 20 may be positioned at a location where the standing wave factor is 0.2 (ξ=0.2). This configuration makes it possible to accumulate carriers in the active layer 20 and release them all at once, thereby emitting short-pulse laser light.

[0019] The upper DBR layer 24 is, for example, a p-type Al layer having an optical film thickness of 1 / 4λc. 0.1 Ga 0.9 As layer and Al 0.9 Ga 0.1 The upper DBR layer 24 may be formed by stacking 20 pairs of layers, each of which is a stack of an Al layer with a thickness of 30 nm. 0.98 Ga 0.02 The oxidized constriction layer 26 is formed by oxidizing a part of the As layer. The oxidized constriction layer 26 is formed by, for example, oxidizing Al 0.98 Ga 0.02The oxidized constriction layer 26 can be formed by oxidizing the As layer from the side of the mesa with water vapor. The oxidized constriction layer 26 has a non-oxidized portion in the center of the mesa and an oxidized portion near the sidewall of the mesa. This allows current injected into the light-emitting element 112 to flow only through the non-oxidized portion, so that only the portion of the light-emitting element 112 that overlaps the center of the mesa in a planar view emits laser light.

[0020] By driving the light emitting element 112, laser light 84 is mainly emitted from a first portion 82 of the top surface of the upper DBR layer 24 where no electrode 74 is provided, and spontaneous emission light 88 is mainly emitted from a second portion 86 which is the end of the active layer 20. The laser light 84 may include a component in a direction parallel to the normal to the semiconductor substrate 10 (the Z direction in FIG. 1). The spontaneous emission light 88 may include a component in a direction parallel to the surface of the semiconductor substrate 10 (the X direction or Y direction in FIG. 1). In other words, the light emitting element 112 emits laser light 84 in a first direction and emits spontaneous emission light 88 in a second direction intersecting the first direction.

[0021] The light emission timing monitor 120 has a light receiving unit 124 that generates an electrical signal in response to incident light. The light emission timing monitor 120 is disposed adjacent to the light emitting unit 110 so that the spontaneous emission light 88 emitted from the second portion 86 of the light emitting element 112 is incident on the light receiving unit 124.

[0022] The determination unit 130 is connected to the light emission timing monitor unit 120 and has the function of detecting the timing at which laser oscillation begins in the light emitting element 112 in response to the spontaneous emission light 88 entering the light receiving unit 124 of the light emission timing monitor unit 120.

[0023] The light emitting device 112 of this embodiment is a VCSEL that has a mechanism for storing carriers in the active layer above a threshold carrier density (carrier density that generates the gain required for laser oscillation), and stores carriers in the active layer 20 and then releases them all at once. The present inventors have discovered for the first time that when attempting to detect the rise of spontaneous emission in such a VCSEL in the same way as detecting the light emission timing in a general VCSEL, the following problem arises.

[0024] 2 and 3 are graphs showing the results of calculations of the optical output waveforms of the light-emitting device. Fig. 2 shows the optical output waveform of a light-emitting device according to a comparative example, and Fig. 3 shows the optical output waveform of the light-emitting device 112 of this embodiment.

[0025] In the case of a typical VCSEL with its active layer positioned at the antinode of the standing wave, oscillation begins and the optical output rises approximately 70 ps after the start of current injection, as shown in Figure 2. The optical output then reaches the peak of the optical waveform associated with relaxation oscillation, and then converges to a steady value.

[0026] On the other hand, the light emitting element 112 of this embodiment emits light having a profile that has a maximum peak value and then converges to a stable value, which is a predetermined light intensity, after the maximum peak value. That is, in the light emitting element 112 of this embodiment, oscillation begins approximately 600 ps after the start of current injection, as shown in FIG.

[0027] 4 is a graph showing the results of calculations of the density of carriers accumulated in the active layer 20 and the change in light intensity over time. The current injected into the light emitting element 112 has the same waveform as in FIG. 3, and injection is assumed to start at 4E-10 seconds on the time axis. The threshold carrier density (the carrier density that converges after the start of oscillation) of the light emitting element 112 is 2.7E+24m -3 (represented by a dashed line in FIG. 4). Note that the light intensity in FIG. 4 is the light intensity of the laser light 84, and the carrier density in FIG. 4 correlates with the light intensity of the spontaneous emission light 88. In other words, the higher the carrier density, the higher the light intensity of the spontaneous emission light 88.

[0028] 4, the carrier density in the active layer 20 starts to increase as soon as current injection begins. The threshold carrier density in the light emitting device 112 of this embodiment is 2.7E+24m -3 However, before the laser oscillation begins, the carriers continue to accumulate beyond the threshold carrier density. After that, when the laser oscillation begins, the carriers are rapidly consumed by stimulated emission and converge to a stable value.

[0029] In this way, in the light emitting device 112 of this embodiment, more carriers than the threshold carrier density are accumulated in the active layer 20. Then, after the start of laser oscillation, the carriers accumulated in the active layer 20 are converted into photons by stimulated emission. This makes it possible to output an optical pulse with a high peak value and a narrow half-width, as shown in FIG. 3. This optical pulse is shorter than the current pulse that drives the VCSEL.

[0030] Here, when we focus on the temporal changes in the increase and decrease in the light intensity of the spontaneous emission light and the increase and decrease in the intensity of the laser light, as shown in Figure 4, we can see that the light intensity (carrier density) of the spontaneous emission light passes its peak value and rapidly drops while the light intensity (light output) of the laser light reaches its peak value. Specifically, there is a delay of about 100 ps between the peak time of the light intensity of the spontaneous emission light and the peak time of the light intensity of the laser light. For this reason, with a short-pulse VCSEL such as the light-emitting element 112 of this embodiment, it is difficult to detect the rising edge of the spontaneous emission light 88 and directly use the detected time as the oscillation timing of the laser light 84.

[0031] As described above, the timing at which the laser light 84 emitted from the light emitting element 112 and the spontaneous emission light 88 reach their intensity peaks differs, and therefore it is preferable that the light receiving unit 124 of the light emission timing monitor unit 120 is configured so as not to receive the laser light 84. To achieve this, for example, a method of arranging a light-shielding film on the side of the light emission timing monitor unit 120 from which the laser light 84 is emitted (the upper side in FIG. 1 ) can be applied. Alternatively, a method of arranging a wavelength filter that transmits the spontaneous emission light 88 but not the laser light 84, that is, a wavelength filter that functions as a bandstop filter or long-pass filter for the wavelength range of the laser light 84, can be applied between the light emitting element 112 and the light emission timing monitor unit 120.

[0032] The spontaneous emission light 88 incident on the light emission timing monitor section 120 is converted into an electrical signal by photoelectric conversion in the light receiving section 124, and is output to the determination section 130 as a light receiving section output together with time information.

[0033] The determination unit 130 detects a change in the amount of the spontaneous emission light 88 over time from the light receiving unit output and time information received from the light emission timing monitor unit 120, and determines whether or not laser light 84 has been output from the light emitting element 112. In other words, the determination unit 130 detects the timing of laser oscillation in the light emitting element 112.

[0034] The sampling interval for the intensity of the spontaneously emitted light 88 can be set appropriately depending on the characteristics required of the device in which the light source device 100 is installed. For example, if the light source device 100 of this embodiment is applied to a distance measuring device, the interval can be set appropriately depending on the distance measuring accuracy required of the distance measuring device. For example, if a distance measurement accuracy of 1 cm distance resolution is required, the time required for light to travel a distance of 1 cm is approximately 67 psec, and the sampling interval for the spontaneously emitted light 88 is preferably about 1 / 10 of that time or less. Note that the sampling of the spontaneously emitted light 88 can be performed at regular intervals depending on the desired distance measurement accuracy by using a timing generator or the like.

[0035] Next, a method for detecting the oscillation timing of the laser beam 84 will be described with reference to Figures 5 and 6. Note that, although some methods for detecting the oscillation timing of the laser beam 84 will be described here, the method for detecting the oscillation timing of the laser beam 84 is not limited to these.

[0036] A first method for detecting the oscillation timing of laser light 84 is to use the differential value of carrier density. Fig. 5 is a graph in which the carrier density values ​​shown in Fig. 4 are differentiated with respect to time and a portion of the time axis is enlarged. The values ​​on the vertical axis in Fig. 5 actually correspond to the differential value of the light output value in light emission timing monitor unit 120.

[0037] The first method is to set a predetermined threshold value for the differential value of the carrier density, and set the time when the differential value of the carrier density becomes equal to or less than the threshold value as the oscillation timing of the laser light 84. For example, in Fig. 5, if the threshold value of the differential value of the carrier density is set to -1 (shown by the dashed dotted line in Fig. 5), the oscillation timing of the laser light 84 will be 1.05E-9 seconds. Note that if the difference between the actual oscillation timing of the laser light and the timing calculated as above is too large for the distance measurement accuracy, the threshold value may be adjusted to a more appropriate value.

[0038] Instead of setting a predetermined threshold value for the carrier density derivative in the graph of FIG. 5, the time midway between the time when the carrier density derivative reaches its maximum value and the time when the carrier density derivative reaches its minimum value can also be estimated as the peak time of the laser light 84.

[0039] A second method for detecting the oscillation timing of the laser light 84 is to use the second derivative of the carrier density. Fig. 6 is a graph obtained by further time-differentiating the carrier density derivative shown in Fig. 5, i.e., by second-deriving the carrier density value shown in Fig. 4. Fig. 6 also shows the change over time in the laser light intensity shown in Fig. 4.

[0040] 6, the time when the second derivative of the carrier density reaches its peak value almost coincides with the time when the laser light intensity reaches its peak value. Therefore, by detecting the time when the second derivative of the light intensity of the spontaneous emission light 88 reaches its peak value, it is possible to detect the time when the intensity of the laser light 84 reaches its peak value.

[0041] Methods for detecting the oscillation timing of the laser beam 84 include the above-described method of detecting based on the decrease in the light intensity of the spontaneous emission light 88, as well as a method using a lookup table. In this case, the delay time between the peak time of the laser beam 84 and the peak time of the spontaneous emission light 88 is measured in advance, including environmental information such as temperature dependency, and a lookup table indicating this relationship is prepared. By referring to the lookup table based on environmental information during operation, the peak time of the laser beam 84 can be appropriately predicted according to the environmental information.

[0042] The distance to the object can be measured accurately from the difference between the time of the laser light emission timing calculated in this way and the time when the light emission timing monitor unit 120 detects the return light of the laser light irradiated on the object.

[0043] The peak time of the spontaneous emission light 88 can be determined, for example, by selecting the time when the output from the light receiving unit becomes maximum within a certain period after the driver current is applied, or by selecting the time when the differential value of the intensity of the spontaneous emission light 88 changes from positive to negative.

[0044] Although the main purpose of this embodiment is to detect the oscillation timing of the laser light, the above configuration can also be used to detect a malfunction of the light source device 100. For example, if it is detected that the amount of the spontaneous emission light 88 does not decrease (does not change), it can be determined that the laser light is not oscillating without monitoring the laser light 84, and therefore the output of the light emission timing monitor unit 120 can be used to detect a malfunction of the light source device 100.

[0045] As described above, according to this embodiment, since the oscillation timing of the laser light is detected using spontaneous emission light, it is possible to improve the measurement accuracy of the oscillation timing of the laser light without reducing the light intensity of the laser light. Furthermore, by incorporating the light source device of this embodiment into a LiDAR (Light Imaging Detection and Ranging) system, it is possible to realize a LiDAR system with high ranging accuracy.

[0046] [Second embodiment] A light source device according to a second embodiment of the present invention will be described with reference to Fig. 7. Components similar to those in the light source device according to the first embodiment are given the same reference numerals, and descriptions thereof will be omitted or simplified. Fig. 7 is a schematic diagram showing an example of the configuration of the light source device according to this embodiment.

[0047] The light source device according to this embodiment has the same basic configuration as the light source device according to Embodiment 1. The light source device 100 according to this embodiment differs from the light source device according to Embodiment 1 in that the light emitting element 112 and the light receiving element 122 constituting the light emission timing monitor unit 120 are formed on the same semiconductor substrate, as shown in FIG.

[0048] The light-emitting element 112 includes a semiconductor substrate 10n of a first conductivity type (e.g., n-type), a lower DBR layer 12n of a first conductivity type (e.g., n-type), a resonator portion 14, an upper DBR layer 24 of a second conductivity type (e.g., p-type), and electrodes 72 and 74. The resonator portion 14 includes a semiconductor layer 16 of a first conductivity type (e.g., n-type), an undoped spacer portion 18, and a semiconductor layer 22 of a second conductivity type (e.g., p-type). The lower DBR layer 12n, the semiconductor layer 16, the undoped spacer portion 18, the semiconductor layer 22, and the upper DBR layer 24 are stacked in this order on one surface of the semiconductor substrate 10n. An active layer 20 is provided in the undoped spacer portion 18. An oxide constriction layer 26 is provided in the upper DBR layer 24.

[0049] The light-receiving element 122 may be a semiconductor light-receiving element configured with a semiconductor laminate structure similar to that of the light-emitting element 112. That is, the light-receiving element 122 includes a semiconductor substrate 10n of a first conductivity type (e.g., n-type), a lower DBR layer 12n of a first conductivity type (e.g., n-type), a resonator portion 14, an upper DBR layer 24, and electrodes 72 and 76. The resonator portion 14 includes a semiconductor layer 16 of a first conductivity type (e.g., n-type), an undoped spacer portion 18, and a semiconductor layer 22 of a second conductivity type (e.g., p-type). The lower DBR layer 12n, the semiconductor layer 16, the undoped spacer portion 18, the semiconductor layer 22, and the upper DBR layer 24 are laminated in this order on one surface of the semiconductor substrate 10n. An active layer 20 is provided in the undoped spacer portion 18. An oxide constriction layer 26 is provided in the upper DBR layer 24. The active layer 20 of the light receiving element 122 serves as the light receiving section 124 of the light emission timing monitor section 120 .

[0050] The semiconductor layer 16, the undoped spacer portion 18, the semiconductor layer 22, and the upper DBR layer 24 are processed into a mesa shape, separating the light emitting element 112 from the light receiving element 122. Although the upper DBR layer 24 to the semiconductor layer 16 are processed into a mesa shape in the example of Fig. 7, the depth separating the light emitting element 112 from the light receiving element 122 is not necessarily limited to this example. That is, it is sufficient that the light emitting element 112 is configured to generate laser oscillation in its central portion, and that the light emitting element 112 and the light receiving element 122 are separated at least in the region extending to the semiconductor substrate 10n side of the oxidized constriction layer 26.

[0051] An electrode 72 that forms an ohmic contact with the semiconductor substrate 10n is provided on the surface of the semiconductor substrate 10n opposite to the surface on which the lower DBR layer 12n is provided. An electrode 74 that forms an ohmic contact with the upper DBR layer 24 is provided on the upper DBR layer 24 of the light-emitting element 112. An electrode 76 that forms an ohmic contact with the upper DBR layer 24 is provided on the upper DBR layer 24 of the light-receiving element 122. A protective film (not shown) may be provided on the sidewalls of the mesa to prevent deterioration of the semiconductor surface.

[0052] The electrode 72 is an electrode common to the light-emitting element 112 and the light-receiving element 122. The electrode 76 can function as a light-shielding film for preventing the laser light 84 from entering the light-receiving portion 124 (the active layer 20 of the light-receiving element 122). The laser light 84 is emitted in a direction perpendicular to the semiconductor substrate 10n (upward in FIG. 7), but reflected light, stray light, etc. may enter the light-receiving portion 124 due to the influence of an optical system, mounted components (not shown), etc. beyond that. In order to prevent the entrance of such reflected light or stray light, the electrode 76 is preferably disposed so as to cover the entire upper portion of the light-receiving portion 124.

[0053] The semiconductor substrate 10n may be, for example, an n-type GaAs substrate. The lower DBR layer 12n may be, for example, an n-type Al 0.1 GaAs layer and Al 0.9 The upper DBR layer 24 may be formed by laminating 35 pairs of layers, each layer consisting of a GaAs layer and a p-type Al layer. Here, λc is the center wavelength of the high reflection band of the lower DBR layer 12, which is 940 nm in this embodiment. The upper DBR layer 24 may be formed by laminating 35 pairs of layers of a GaAs layer and a p-type Al layer with an optical film thickness of 1 / 4 λc. 0.1 Ga 0.9 As layer and Al 0.9 Ga 0.1 The resonator portion 14 may be configured in the same manner as the light emitting device 112 of the first embodiment, with 20 pairs of laminated bodies each including an As layer counted as one pair.

[0054] The light-emitting element 112 is driven by a forward bias voltage supplied between the electrode 72 and the electrode 74. The current injected into the light-emitting element 112 flows only through the non-oxidized portion in the center of the mesa where the oxidized constriction layer 26 is not provided, and therefore only the portion of the light-emitting element 112 that overlaps with the center of the mesa in a planar view emits laser light. The light-receiving element 122 is driven by a reverse bias voltage supplied between the electrode 72 and the electrode 76, and detects the amount of spontaneously emitted light 88 incident on the active layer 20 (light-receiving unit 124). The determination unit 130 detects the oscillation timing of the laser light 84 based on the light amount information for each hour received from the light-receiving element 122 (light-emission timing monitor unit 120).

[0055] Next, the positional relationship between the light emitting element 112 and the light receiving element 122 will be described with reference to FIGS.

[0056] Fig. 8 is a top view showing the positional relationship between the light emitting element and the light receiving element in the light source device of this embodiment. The cross section of the light emitting element and the light receiving element in Fig. 7 corresponds to the cross section taken along line AA' in Fig. 8. In the coordinate systems shown in Figs. 7 and 8, the XY plane is a plane parallel to the surface of the semiconductor substrate 10n, and the Z direction is a direction parallel to the normal direction of the semiconductor substrate 10n.

[0057] A pad electrode 74P is connected to the electrode 74. The pad electrode 74P is an electrode to which wiring for supplying voltage to the electrode 74 is connected. The electrode 74 and the pad electrode 74P may be configured by a single continuous electrode pattern, for example, as shown in Fig. 8. The portion indicated by the dashed line in Fig. 8 corresponds to the outer periphery of the electrode 74 in Fig. 7.

[0058] Similarly, a pad electrode 76P is connected to the electrode 76. The pad electrode 76P is an electrode to which wiring for supplying voltage to the electrode 76 is connected. The electrode 76 and the pad electrode 76P may be configured by a single continuous electrode pattern, as shown in Fig. 8, for example. The portion indicated by the dashed line in Fig. 8 corresponds to the electrode 76 in Fig. 7.

[0059] Here, the light emitting element 112 and the light receiving element 122 are assumed to be arranged side by side in the X direction in the coordinate system shown in Fig. 8. The distance from the end face of the light emitting element 112 to the end face of the active layer 20 of the light receiving element 122 is assumed to be L1. In addition, in the coordinate system shown in Fig. 8, the length of one side of the electrode 76 along the X direction is assumed to be L2, and the length of the electrode 76 along the Y direction is assumed to be L3.

[0060] 9 is a graph showing the distance L1 dependency of the output of the light receiving element 122 and the dark current flowing between the electrodes 72 and 76. In FIG. 9, the solid line represents the output of the light receiving element 122, and the dotted line represents the dark current flowing between the electrodes 72 and 76 of the light receiving element 122. Here, it is assumed that the lengths L2 and L3 are both 100 μm.

[0061] 9, the dark current flowing between the electrodes 72 and 76 of the light receiving element 122 is constant regardless of the distance L1 from the end face of the light emitting element 112 to the end face of the active layer 20 of the light receiving element 122. In other words, once the configuration of the light receiving element 122 is determined, the dark current flowing between the electrodes 72 and 76 is constant regardless of the distance L1.

[0062] On the other hand, the output of the light receiving element 122 tends to increase as the distance L1 becomes shorter. In the example of FIG. 9, the output increases sharply when the distance L1 becomes less than approximately 30 μm. When the distance L1 becomes shorter than 11 μm, the output of the light receiving element 122 exceeds the dark current. In other words, by making the distance L1 shorter than 11 μm, the spontaneous emission light 88 emitted from the light emitting element 112 can be detected by the light receiving element 122. In order to accurately detect an increase or decrease in the amount of the spontaneous emission light 88, it is preferable to set the distance L1 to 8 μm or less. By setting the distance L1 to 8 μm or less, the S / N ratio becomes 2 or more.

[0063] The relationship between the output of the light-receiving element 122 and the distance L1, as well as the value of the dark current, varies depending on the area (lengths L2 and L3) of the light-receiving element 122. Increasing the area of ​​the light-receiving element 122 increases the dark current, but also increases the amount of detected light, i.e., the detected current value. In this case, the S / N ratio remains unchanged, but the large detected current value provides advantages such as increased resistance to noise in signal processing by the determination unit 130, easier circuit design, and reduced required precision in circuit design. From this perspective, it is preferable to increase the area of ​​the light-receiving element 122 and the detected current value.

[0064] When the light-emitting element 112 and the light-receiving element 122 are formed on the same semiconductor substrate as in this embodiment, the distance L1 between the light-emitting element 112 and the light-receiving element 122 can be accurately controlled with an accuracy according to the process manufacturing accuracy of the photolithography process.

[0065] In this embodiment, the light-emitting section 110 has one light-emitting element 112, but the number of light-emitting elements 112 that the light-emitting section 110 has is not limited to one, and the light-emitting section 110 may have multiple light-emitting elements 112.

[0066] FIG. 10 shows a case where the light-emitting unit 110 has three light-emitting elements 112 arranged in a straight line in a plan view. When multiple light-emitting elements 112 are arranged in a straight line, it is preferable that the light-receiving element 122 be arranged so that its end, which is the light-receiving surface, is parallel to the direction in which the light-emitting elements 112 are arranged, as shown in FIG. 10. By arranging the light emission timing monitor unit 120 in this way for multiple light-emitting elements 112 that are driven simultaneously, the S / N ratio remains unchanged, but the detected current value can be increased. Note that the number of light-emitting elements 112 included in the light-emitting unit 110 is not limited to three.

[0067] FIG. 11 shows a case where the light-emitting unit 110 has four light-emitting elements 112 arranged to surround a light-receiving element 122 in a plan view. By arranging the light emission timing monitor unit 120 in this manner for multiple light-emitting elements 112 that are driven simultaneously, the amount of light incident on the light emission timing monitor unit 120, i.e., the amount of signal, increases, thereby improving the S / N ratio. Here, as shown in FIG. 11, it is preferable to arrange the extraction electrode (the portion connected to the electrode 74) from the mesa of the light-emitting element 112 so as to avoid the light-receiving element 122 side as much as possible. This makes it possible to reduce the proportion of spontaneously emitted light components blocked from the light-emitting elements 112, thereby increasing the amount of light detected by the light emission timing monitor unit 120. Note that the number of light-emitting elements 112 included in the light-emitting unit 110 is not limited to four.

[0068] In this embodiment, the light emitting element 112 and the light receiving element 122 are formed using the same semiconductor laminate structure, but the light emitting element 112 and the light receiving element 122 do not necessarily have to have the same semiconductor laminate structure. For example, a semiconductor laminate structure that constitutes the light receiving element 122 may be formed on top of the semiconductor laminate structure that constitutes the light emitting element 112. In this case, the semiconductor layer added for the light receiving element 122 is removed from the portion of the light emitting element 112. With this configuration, the element design of the light receiving element 122 can be carried out without being limited by the element design of the light emitting element 112.

[0069] As described above, according to this embodiment, since the oscillation timing of the laser light is detected using spontaneous emission light, it is possible to improve the measurement accuracy of the oscillation timing of the laser light without reducing the light intensity of the laser light. Furthermore, by incorporating the light source device of this embodiment into a LiDAR system, it is possible to realize a LiDAR system with high ranging accuracy.

[0070] [Third embodiment] A light source device according to a third embodiment of the present invention will be described with reference to Figs. 12 and 13. Components similar to those of the light source devices according to the first and second embodiments are given the same reference numerals, and descriptions thereof will be omitted or simplified. Fig. 12 is a schematic diagram showing an example of the configuration of the light source device according to this embodiment. Fig. 13 is a top view showing an example of the configuration of the light source device according to this embodiment.

[0071] The light source device 100 according to this embodiment has a basic configuration similar to that of the light source device 100 according to the first embodiment. The light source device 100 according to this embodiment differs from the light source device 100 according to the first embodiment in that the light emitting element 112 and the light receiving element 122 are formed on the same semiconductor substrate 10n, as shown in Fig. 12. However, the light source device 100 according to this embodiment differs from the light source device 100 according to the second embodiment in that the light receiving element 122 is formed on a semiconductor substrate different from the semiconductor substrate 10n and is bonded onto the semiconductor substrate 10n.

[0072] That is, the light receiving element 122 of this embodiment includes a semiconductor substrate 30 of a third conductivity type, a semiconductor layer 32 of the third conductivity type (e.g., n-type), a light receiving layer 34, a semiconductor layer 36 of a fourth conductivity type (e.g., p-type) different from the third conductivity type, and electrodes 76 and 78. The semiconductor layer 32, the light receiving layer 34, the semiconductor layer 36, and the electrode 78 are stacked in this order on one surface of the semiconductor substrate 30. This forms a pin structure photodiode made up of the semiconductor layer 32, the light receiving layer 34, and the semiconductor layer 36. The electrode 76 is provided on the other surface of the semiconductor substrate 30. The light receiving element 122 configured in this manner is bonded onto a semiconductor substrate 10n on which the light emitting element 112 is provided.

[0073] The light receiving element 122 of this embodiment can be manufactured, for example, as follows. First, the semiconductor layer 32, the light-receiving layer 34, and the semiconductor layer 36 are epitaxially grown on the semiconductor substrate 30. Next, the electrode 78a is formed on the semiconductor layer 36. In addition, the electrode 76 is formed on the back surface side of the semiconductor substrate 30.

[0074] Next, the timing monitor substrate thus formed is turned over and diced to have a predetermined area required for the light receiving element 122, and the individual light receiving elements 122 are picked up.

[0075] On the other hand, an electrode 78b is formed in advance on the portion of the substrate on which the light-emitting element 112 is provided, where the light-receiving element 122 will be installed. Fig. 13 is a top view of the substrate on which the light-emitting element 112 is provided, before the light-receiving element 122 is installed. The dotted line area shown within the electrode 78b is the portion where the light-receiving element 122 will be installed.

[0076] Next, the picked-up light receiving element 122 is bonded onto electrode 78b with electrode 78a facing downward. The bonding between the light receiving element 122 and the substrate on which the light emitting element 112 is formed can be performed, for example, by intermetallic bonding between the gold constituting electrode 78a and the gold constituting electrode 78b. The bonding between the light receiving element 122 and the substrate on which the light emitting element 112 is formed does not necessarily have to be performed by intermetallic bonding, and they may be fixed using an adhesive or the like.

[0077] By configuring the light source device 100 in this manner, it becomes possible to design the material, film thickness, area, etc. of the absorption layer 34 of the light receiving element 122 independently of the epitaxial structure of the light emitting element 112. Furthermore, since the height of the absorption layer 34 can be set according to the thickness of each layer and the bonding accuracy, it becomes possible to control the absorption layer 34 to an appropriate position according to the position of the active layer 20 of the light emitting element 112.

[0078] From the viewpoint of efficiently detecting the spontaneous emission light 88 emitted from the active layer 20, the light-receiving layer 34 is preferably disposed at a height that includes the height at which the active layer 20 is provided. The light-receiving layer 34 is preferably as thick as possible, and ideally, the height of the center of the thickness of the light-receiving layer 34 is located at the height of the active layer 20. However, due to limitations in etching the resonator portion 14 and the like, and limitations in placing the light-receiving element 122 on the substrate, the height of the light-receiving layer 34 does not necessarily have to be located at the height of the active layer 20. Note that the height referred to here refers to the distance from the surface of the semiconductor substrate 10n.

[0079] In this case, for example, if a light receiving element 122 having a light receiving layer 34 made of a silicon layer with a film thickness of 5 μm and an area of ​​30 μm × 30 μm is placed at a distance of 10 μm from the end of the light emitting element 112, the spontaneous emission light 88 can be detected with an S / N ratio of 100 or more.

[0080] When the height of the center of the film thickness of the light-receiving layer 34 does not match the height of the active layer 20, it is necessary to consider the components of the spontaneous emission light 88 that change with height. Specifically, the light-receiving sensitivity of the spontaneous emission light 88 is determined depending on the volume of the light-receiving layer 34, and the dark current is determined depending on the area of ​​the light-receiving layer 34. Furthermore, the proportion of the components of the spontaneous emission light 88 emitted from the light-emitting element 112 that can be received is determined by taking into account not only the distance from the light-emitting element 112 but also the influence of the FFP (Far Field Pattern) of the components of the spontaneous emission light 88, which changes depending on the height. Taking these factors into consideration comprehensively, the element configuration and the distance between elements are set so that the output of the light emission timing monitor unit 120 is equal to or greater than the dark current value.

[0081] 12, the electrode 78 of the light-receiving element 122 is formed at approximately the same height as the resonator portion 14 of the light-emitting element 112, but if good electrical contact can be obtained between the semiconductor layer 36 and the semiconductor substrate 10n, the electrode 78 does not have to be provided. In this case, the electrode 72 can be used as a common electrode for the light-emitting element 112 and the light-receiving element 122.

[0082] In this embodiment, the light emitting section 110 has one light emitting element 112, but similar to the second embodiment, the light emitting section 110 may have a plurality of light emitting elements 112.

[0083] As described above, according to this embodiment, since the oscillation timing of the laser light is detected using spontaneous emission light, it is possible to improve the measurement accuracy of the oscillation timing of the laser light without reducing the light intensity of the laser light. Furthermore, by incorporating the light source device of this embodiment into a LiDAR system, it is possible to realize a LiDAR system with high ranging accuracy.

[0084] [Fourth embodiment] A light source device according to a fourth embodiment of the present invention will be described with reference to Fig. 14. Components similar to those of the light source devices according to the first to third embodiments are given the same reference numerals, and descriptions thereof will be omitted or simplified. Fig. 14 is a schematic diagram showing an example of the configuration of the light source device according to this embodiment.

[0085] 14, in the light source device 100 according to this embodiment, the light emitting element 112 constituting the light emitting unit 110 and the light receiving element 122 constituting the light emission timing monitor unit 120 are configured as separate components. The light receiving element 122 may be configured as a photodiode with a pin structure similar to that of the third embodiment. The light emitting element 112 is mounted on a substrate 40. The light receiving element 122 is supported by a support member 42 such as a stem so that the surface of the light receiving unit 124 faces the second portion 86 of the light emitting element 112, and is mounted on the substrate 40.

[0086] Here, the relationship between the amount of spontaneously emitted light 88 emitted from the light-emitting element 112 and the distance between the second portion 86 and the light-receiving unit 124 will be described with reference to FIG. 15. FIG. 15 is a graph showing the results of measuring the relationship between the output of the light-receiving element 122 and the distance between the second portion 86 and the light-receiving unit 124. In FIG. 15, the vertical axis represents the output of the light-receiving element 122 (PD output), and the horizontal axis represents the distance between the second portion 86 and the light-receiving unit 124. The amount of current injected into the light-emitting element 112 used in the measurement was 1 mA, which is below the threshold current. Furthermore, a light-receiving element 122 with a large light-receiving area was used for the measurement, and FIG. 15 shows the current value when the light-receiving area is converted to a value of φ0.1 mm.

[0087] As shown in FIG. 15 , as the distance between the light-emitting element 112 and the light-receiving element 122 increases, the output of the light-receiving element 122 decreases significantly. If the output of the light-receiving element 122 falls below the dark current value, it becomes impossible to detect an increase or decrease in the spontaneous emission light 88. For example, if the dark current is 100 pA in the light-receiving element 122 with a light-receiving area of ​​φ0.1 mm, in the example of FIG. 15 , when the light-emitting element 112 and the light-receiving element 122 are separated by approximately 6 mm, the output of the light-receiving element 122 and the dark current become approximately equal in magnitude. In other words, the S / N ratio becomes less than 1, making it difficult to detect an increase or decrease in the spontaneous emission light 88. On the other hand, when the distance between the light-emitting element 112 and the light-receiving element 122 is reduced to approximately 2 mm, the output of the light-receiving element 122 can increase to approximately 10 times the dark current.

[0088] If the distance between the second portion 86 of the light emitting element 112 and the light receiving portion 124 of the light receiving element 122 is L [m], it is preferable that the distance L satisfies the relationship of the following formula (1). In formula (1), P [W] is the total amount of spontaneously emitted light 88 emitted from the second portion 86, S [m 2 ] is the light receiving area of ​​the light receiving section 124 of the light receiving element 122 , Q [A / W] is the light receiving sensitivity of the light receiving element 122 , and Da [A] is the dark current value of the light receiving element 122 . P×(S / 4πL 2 )×Q > Da …(1)

[0089] Up to now, it has been explained that the spontaneously emitted light 88 from the light emitting element 112 is incident on the light receiving unit 124, but in reality, there is a possibility that part of the laser light 84 may be incident on the light receiving unit 124 due to reflection from an optical system (not shown), etc. In such a case, for example, as shown in FIG. 14 , a wavelength filter 126 may be arranged on the incident surface side of the spontaneously emitted light 88 to the light receiving unit 124.

[0090] Here, the setting of the transmission wavelength band of the wavelength filter 126 when separating the spontaneous emission light 88 and the laser light 84 using the wavelength filter 126 will be described.

[0091] Fig. 16 is a graph showing the calculated gain spectrum and spontaneous emission spectrum of a quantum well having an InGaAs well layer with a ground-level transition wavelength of 940 nm. In Fig. 16, the gain spectrum is shown by a dotted line, and the spontaneous emission spectrum is shown by a solid line.

[0092] As shown in Figure 16, the peak wavelength of the gain spectrum is approximately 940 nm. Therefore, when optimizing the design in the state shown in Figure 16, the resonant wavelength λc of the surface-emitting laser is set to approximately 940 nm, where the gain is highest and laser light can be extracted efficiently. On the other hand, the spontaneous emission light has a spectrum shape that is largely spread toward wavelengths shorter than 940 nm. Therefore, as an optical filter for blocking the laser light and transmitting only the spontaneous emission light in large quantities, it is preferable to use a so-called short-pass filter that transmits light shorter than a specific wavelength λco and reflects or absorbs light longer than λco.

[0093] Since the spectral width of laser light is generally 5 nm or less, the wavelength λco only needs to satisfy the relationship of the following equation (2). λco < λc-5 [nm] …(2)

[0094] However, in reality, there may be manufacturing variations of about ±10 nm in the resonant wavelength λc of a surface-emitting laser. It is also necessary to consider manufacturing variations in the short-pass filter and the wavelength width (about 10 nm) required for the intensity of transmitted light to decrease to nearly zero near the wavelength λco. From this perspective, it is more preferable that the wavelength λco satisfy the relationship of the following equation (3). λco ≦ λc-30 [nm] …(3)

[0095] According to equation (3), when the resonant wavelength λc is 940 nm, the wavelength λco is 910 nm. In Figure 16, the spectrum of the spontaneous emission light extends to wavelengths shorter than 910 nm, so it can be seen that by using an optical filter with a wavelength λco of 910 nm, it is possible to detect only the spontaneous emission light and thereby detect the oscillation timing.

[0096] In many cases, surface-emitting lasers are designed with the gain peak wavelength at room temperature shifted toward the shorter wavelength side so that the laser oscillation wavelength and the gain peak wavelength approach each other as the temperature rises. The amount of shift of the gain peak wavelength at room temperature is generally set to about 20 nm. In such cases, the peak wavelength of the gain spectrum of the active layer 20 is designed to be about 20 nm shorter than the resonant wavelength λc of the surface-emitting laser.

[0097] FIG. 17 is a graph showing the results of calculations of the gain spectrum and the spontaneous emission spectrum when the gain peak wavelength is shifted 20 nm toward the shorter wavelength side.

[0098] In this case, since the resonant wavelength λc is near 940 nm at room temperature, as in the case described above, the wavelength λco is preferably less than λc-5 nm, and more preferably λc-30 nm or less. It can be seen that at room temperature, there are many components of specific wavelengths in the spontaneous emission light, for example, components on the shorter wavelength side than the wavelength λco of 910 nm. Therefore, at room temperature, more of the spontaneous emission light can be used to detect the oscillation timing. Furthermore, at high temperatures, the relationship between the gain spectrum and the spontaneous emission light spectrum approaches that shown in Figure 16, so that only the spontaneous emission light is transmitted even at high temperatures, making it possible to detect the oscillation timing.

[0099] In addition, when the amount of spontaneously emitted light 88 incident on the light receiving unit 124 is reduced by the wavelength filter 126, the distance L can be calculated by subtracting the amount of spontaneously emitted light reduced by the wavelength filter 126 from the total amount P of spontaneously emitted light, which is one of the parameters in equation (1), to obtain the total amount P'.

[0100] In this embodiment, the light emitting section 110 has one light emitting element 112, but similar to the second embodiment, the light emitting section 110 may have a plurality of light emitting elements 112.

[0101] As described above, according to this embodiment, since the oscillation timing of the laser light is detected using spontaneous emission light, it is possible to improve the measurement accuracy of the oscillation timing of the laser light without reducing the light intensity of the laser light. Furthermore, by incorporating the light source device of this embodiment into a LiDAR system, it is possible to realize a LiDAR system with high ranging accuracy.

[0102] [Fifth embodiment] A light source device according to a fifth embodiment of the present invention will be described with reference to Fig. 18. Components similar to those of the light source devices according to the first to fourth embodiments are given the same reference numerals, and descriptions thereof will be omitted or simplified. Fig. 18 is a schematic diagram showing an example of the configuration of a light source device according to this embodiment.

[0103] The light source device 100 according to this embodiment differs from the light source device 100 according to the second embodiment in the configuration of the light emitting element 112. That is, as shown in FIG. 18 , the light emitting element 112 according to this embodiment further includes an undoped spacer section 50 having a saturable absorbing layer 52 between the lower DBR layer 12 and the semiconductor layer 16. The undoped spacer section 18 also includes a three-layer active layer 20. The layer (the undoped spacer section 50 and the resonator section 14) located between the lower DBR layer 12 and the upper DBR layer 24 constitutes the resonator spacer section. The electrode 72 is provided on the semiconductor layer 16 and is in ohmic contact with the semiconductor layer 16. Other points are the same as those of the light source device 100 according to the second embodiment.

[0104] The resonator section 14 is formed by a pin junction including a semiconductor layer 16 of a first conductivity type (e.g., n-type), an undoped spacer section 18, and a semiconductor layer 22 of a second conductivity type (e.g., p-type). Each of the three active layers 20 arranged in the undoped spacer section 18 may be formed by a multiple quantum well including four quantum well layers, each of which has an 8-nm-thick InGaAs well layer sandwiched between 10-nm-thick AlGaAs barrier layers. In this case, the resonator section 14 includes a total of 12 quantum well layers. The semiconductor layer 16 may be formed by an n-type GaAs layer, the semiconductor layer 22 may be formed by a p-type GaAs layer, and the remaining portion of the undoped spacer section 18 may be formed by an undoped AlGaAs layer.

[0105] The resonator section 14 is made up of a pin junction, which is also found in a typical VCSEL, and has a similar configuration to a resonator section that includes an active layer within the i-layer. However, the number of quantum well layers in the resonator section 14 is greater than the number of quantum well layers (approximately three) found in a typical VCSEL. The effective resonator length in the resonator section 14 is 10 μm.

[0106] In this embodiment, these three active layers 20 are positioned between the antinode and node of the standing wave, rather than at the antinode of the standing wave, as is the case in typical VCSEL designs. This allows for optimization of the optical response characteristics when a drive current is injected. Furthermore, while the optical confinement factor for the standing wave is typically in the range of 1.5 to 2.0 in typical VCSELs, this is intentionally set low at approximately 0.35 in this embodiment. Furthermore, the AlGaAs barrier layers have a smaller bandgap than the barrier layers in the quantum wells of typical VCSELs, allowing carriers to accumulate in the barrier layers as well. As a result, although the number of InGaAs well layers where carriers accumulate is 12, carrier accumulation in the AlGaAs barrier layers also allows for carrier accumulation equivalent to approximately 20 layers in a typical quantum well. The Al composition of the AlGaAs barrier layers is preferably 0 to 30%.

[0107] The undoped spacer portion 50 is a structure not found in typical VCSELs. The saturable absorbing layer 52 may be formed of a multiple quantum well structure including three quantum well layers, each of which has an 8-nm-thick InGaAs well layer sandwiched between 10-nm-thick AlGaAs barrier layers. The remaining portions of the undoped spacer portion 50 may be formed of undoped GaAs layers.

[0108] Next, the operation of the light emitting element 112 of this embodiment will be described with reference to FIGS. 2 and 3 are graphs showing the results of calculations of the optical output waveform of a light-emitting device. Fig. 2 shows the optical output waveform of a light-emitting device according to a comparative example, and Fig. 3 shows the optical output waveform of light-emitting device 112 according to this embodiment. The light-emitting device according to the comparative example is a VCSEL with a general configuration that does not include a saturable absorption layer, has three quantum well layers, and is designed with a cavity length of 1λ.

[0109] In the case of a typical semiconductor light-emitting device, oscillation begins and optical output rises approximately 70 ps after the start of current injection, as shown in Figure 2. The optical output then reaches a peak in the optical waveform associated with relaxation oscillation, and then converges to a steady value.

[0110] On the other hand, the light-emitting device 112 according to this embodiment emits 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 light-emitting device 112 according to this embodiment, oscillation begins approximately 600 ps after the start of current injection, as shown in FIG. 3 . This delay in the start of oscillation is due to the large effective volume of the active layer 20 and the fact that oscillation is inhibited for a certain period of time after the start of current injection due to light absorption in the saturable absorbing layer 52. When light is absorbed in the saturable absorbing layer 52, the absorbed light is accumulated as carriers in the saturable absorbing layer 52. As the light is absorbed, the number of carriers increases. When the carrier density in the saturable absorbing layer 52 reaches the transparent carrier density, the saturable absorbing layer 52 no longer absorbs light. As a result, the effect of inhibiting laser oscillation disappears, and the semiconductor light-emitting device begins laser oscillation.

[0111] The purpose of inhibiting laser oscillation for a certain period of time by the saturable absorbing layer 52 is to accumulate carriers exceeding a threshold carrier density in the active layer 20. Here, the threshold carrier density is the carrier density that generates the gain required for laser oscillation.

[0112] 4 is a graph showing the change over time in the density of carriers accumulated in the active layer 20 and the light intensity. The current injected into the light emitting element 112 has the same waveform as in FIG. 3, and injection starts at 4E-10 seconds on the time axis.

[0113] 4, the carrier density in the active layer 20 starts to increase with the start of current injection. The threshold carrier density (the carrier density that converges after the start of oscillation) in the light emitting device 112 of this embodiment is 2.7E+18 cm -3 However, before the laser oscillation begins, the carriers continue to accumulate beyond the threshold carrier density. After that, when the laser oscillation begins, the carriers are rapidly consumed by stimulated emission and converge to a stable value.

[0114] In this way, in the light emitting device 112 of this embodiment, a larger number of carriers than the threshold carrier density are accumulated in the active layer 20. Then, after the start of laser oscillation, the carriers accumulated in the active layer 20 are converted into photons by stimulated emission. This makes it possible to output an optical pulse with a high peak value and a short half-width, as shown in FIG.

[0115] Carriers exceeding the threshold carrier density can be accumulated in the active layer 20 because laser oscillation is suppressed for a certain period of time using the saturable absorbing layer 52. By achieving such a high carrier density, an optical pulse with a high peak value and a short pulse width can be generated inside the light-emitting element after oscillation. This optical pulse is shorter than the current pulse that drives the light-emitting element 112. In this example, the peak intensity of the laser light is more than three times the intensity of the steady-state laser light.

[0116] For comparison, the operating principle of a general VCSEL will be explained with reference to FIG. In the case of a typical VCSEL, as in the case of the light-emitting device 112 of this embodiment, the carrier density in the active layer rises to the threshold carrier density (shown by the dashed-dotted line in FIG. 19) as soon as current injection begins. Before laser oscillation begins, the carrier density temporarily exceeds the threshold carrier density and continues to accumulate. Then, once oscillation begins, the carriers are rapidly consumed by stimulated emission and converge to a stable value.

[0117] Comparing the characteristics of a typical VCSEL shown in Fig. 19 with the characteristics of the light-emitting device 112 of this embodiment shown in Fig. 4, in the typical VCSEL, the period during which carriers accumulate beyond the threshold carrier density and the period during which carriers are rapidly consumed by stimulated emission are very short. Also, the intensity peak of the spontaneous emission light and the timing of laser light oscillation are almost the same. Also, the peak light intensity of the laser light is about twice the light intensity of the steady-state laser light.

[0118] 4 and 19 are merely examples, and the lengths of these times and periods will vary depending on the configuration of the light-emitting device. For example, as the number and volume of well layers increase, the carrier accumulation time will become longer under the same current injection conditions.

[0119] Next, an example of a method for manufacturing the light emitting device 112 according to this embodiment will be described below. First, the semiconductor layers constituting the lower DBR layer 12, the undoped spacer section 50, the resonator section 14, and the upper DBR layer 24 are grown on the semiconductor substrate 10 by metal organic chemical vapor deposition or molecular beam epitaxy.

[0120] Next, photolithography and etching techniques are used to pattern the upper DBR layer 24, the semiconductor layer 22, and the non-doped spacer portion 18. As a result, a columnar mesa having a diameter of, for example, about 30 μm is formed.

[0121] Next, thermal oxidation is performed in a water vapor atmosphere at about 450° C. to remove Al from the upper DBR layer 24. 0.98 Ga 0.02The As layer is oxidized from the sidewall of the mesa to form the oxidized constriction layer 26. At this time, by controlling the oxidation time, the Al 0.98 Ga 0.02 In the As layer, a non-oxidized portion is formed in the center of the mesa, and an oxidized portion (oxidized constriction layer 26) is formed near the sidewall of the mesa. 0.98 Ga 0.02 The diameter of the non-oxidized portion of the As layer is controlled to be about 10 μm.

[0122] Next, using photolithography and vacuum deposition, an electrode 74 that will serve as a p-side electrode is formed on the upper surface of the mesa, and then an electrode 72 that will serve as an n-side electrode is formed on the upper surface of the semiconductor layer 16 that is exposed by etching. The electrode 74 has a circular ring-shaped pattern, and the central opening serves as a circular window for light extraction.

[0123] Next, a protective film (not shown) is formed using photolithography and plasma CVD so as to cover the top and side surfaces of the mesa on which the electrodes 72 and 74 are provided, and the top surface of the semiconductor layer 16.

[0124] Next, in order to obtain good electrical properties, heat treatment is carried out in a nitrogen atmosphere to alloy the interface between the electrode material and the semiconductor material, thereby completing the light emitting device 112 of this embodiment.

[0125] The light-emitting element 112 and the light-receiving element 122 are separated by dry etching, wet etching, or the like, as in the second embodiment. A portion of the layers above the semiconductor layer 16 is removed during processing, and the remaining portion is formed into a mesa shape. In the example of FIG. 18 , the area from the upper DBR layer 24 to the non-doped spacer portion 18 is processed into a mesa shape, but the depth separating the light-emitting element 112 and the light-receiving element 122 is not necessarily limited to this example. That is, the light-emitting element 112 only needs to be configured to generate laser oscillation at its center, and the light-emitting element 112 and the light-receiving element 122 only need to be separated by at least the region extending to the semiconductor substrate 10n side of the oxidized constriction layer 26.

[0126] The electrode 72 is an electrode common to the light-emitting element 112 and the light-receiving element 122. The light-emitting element 112 is driven by a forward bias voltage supplied between the electrode 72 and the electrode 74. The current injected into the light-emitting element 112 flows only through the non-oxidized portion in the center of the mesa where the oxidized constriction layer 26 is not provided, and therefore only the portion of the light-emitting element 112 that overlaps with the center of the mesa in a planar view oscillates as a laser. The light-receiving element 122 is driven by a reverse bias voltage supplied between the electrode 72 and the electrode 76, and detects the amount of spontaneously emitted light 88 incident on the active layer 20 (light-receiving unit 124). The determination unit 130 detects the oscillation timing of the laser light 84 based on the light amount information per unit time received from the light-receiving element 122 (light-emission timing monitor unit 120).

[0127] In this embodiment, the light emitting section 110 has one light emitting element 112, but similar to the second embodiment, the light emitting section 110 may have a plurality of light emitting elements 112.

[0128] Furthermore, in this embodiment, an example has been shown in which the light emission timing monitor unit 120 is configured using the light receiving element 122 of the second embodiment, but the light receiving element 122 that configures the light emission timing monitor unit 120 is not limited to this. The light receiving element 122 that configures the light emission timing monitor unit 120 may be the light receiving element 122 described in other embodiments.

[0129] As described above, according to this embodiment, since the oscillation timing of the laser light is detected using spontaneous emission light, it is possible to improve the measurement accuracy of the oscillation timing of the laser light without reducing the light intensity of the laser light. Furthermore, by incorporating the light source device of this embodiment into a LiDAR system, it is possible to realize a LiDAR system with high ranging accuracy.

[0130] [Sixth embodiment] A light source device according to a sixth embodiment of the present invention will be described with reference to Fig. 20. Components similar to those of the light source devices according to the first to fifth embodiments are given the same reference numerals, and descriptions thereof will be omitted or simplified. Fig. 20 is a schematic diagram showing an example of the configuration of a light source device according to this embodiment.

[0131] The light source device 100 according to this embodiment differs from the light source devices 100 of the previous embodiments in the configuration of the light emitting element 112. That is, as shown in Fig. 20, the light emitting element 112 of this embodiment has a semiconductor substrate 10n of a first conductivity type (e.g., n-type), a lower DBR layer 12n of the first conductivity type, an active region 60, an undoped spacer portion 18, a semiconductor layer 22, and an upper DBR layer 24. The light emitting element 112 of this embodiment also has electrodes 72, 74, and 80. The lower DBR layer 12n, the active region 60, the undoped spacer portion 18, the semiconductor layer 22, and the upper DBR layer 24 are stacked in this order on one surface of the semiconductor substrate 10n.

[0132] The active region 60 has, in order from the lower DBR layer 12n side, a saturable absorbing layer 62, a junction layer 64 of a second conductivity type (for example, p-type), a tunnel junction 66, and a junction layer 68 of a first conductivity type. The tunnel junction 66 is formed by a highly doped semiconductor layer of the second conductivity type (for example, p-type) in contact with the junction layer 64. ++ a highly doped semiconductor layer of the first conductivity type (for example, n ++ The junction between these highly doped semiconductor layers forms a tunnel junction.

[0133] In the tunnel junction 66, charge carriers are effectively recycled by moving from the valence band to the conduction band, so that electrons from one side and holes from the other side pump the active layer structure of the undoped spacer section 18 as well as the saturable absorbing layer 62. In this embodiment, an electrode 80 is further provided between the saturable absorbing layer 62 and the tunnel junction 66 so that the currents flowing through the saturable absorbing layer 62 and the active layer structure of the undoped spacer section 18 can be controlled separately.

[0134] That is, the light emitting element 112 of this embodiment is a VCSEL with a three-electrode configuration having electrodes 72, 74, and 80. Such a three-electrode configuration makes it easier to control the oscillation timing of the laser light. However, since environmental changes such as temperature still cause a mismatch between the driver drive timing and the oscillation timing of the laser light, the configuration of this embodiment, which has a mechanism for measuring the oscillation timing of the laser light, is effective.

[0135] In this embodiment, the light emitting section 110 has one light emitting element 112, but similar to the second embodiment, the light emitting section 110 may have a plurality of light emitting elements 112.

[0136] Furthermore, in this embodiment, an example has been shown in which the light emission timing monitor unit 120 is configured using the light receiving element 122 of the fourth embodiment, but the light receiving element 122 that configures the light emission timing monitor unit 120 is not limited to this. The light receiving element 122 that configures the light emission timing monitor unit 120 may be the light receiving element 122 described in the other embodiments.

[0137] As described above, according to this embodiment, since the oscillation timing of the laser light is detected using spontaneous emission light, it is possible to improve the measurement accuracy of the oscillation timing of the laser light without reducing the light intensity of the laser light. Furthermore, by incorporating the light source device of this embodiment into a LiDAR system, it is possible to realize a LiDAR system with high ranging accuracy.

[0138] [Seventh embodiment] A light source device according to the seventh embodiment of the present invention will be described with reference to Fig. 21 and Fig. 22. Components similar to those of the light source devices according to the first to sixth embodiments are given the same reference numerals, and descriptions thereof will be omitted or simplified. Fig. 21 and Fig. 22 are schematic diagrams showing an example of the configuration of the light source device according to this embodiment.

[0139] In the first to sixth embodiments, the spontaneously emitted light 88 emitted from the second portion 86 of the light-emitting element 112 is detected by the light-receiving element 122, but it is also possible to detect the spontaneously emitted light 88 emitted from the first portion 82 of the light-emitting element 112 by the light-receiving element 122. In this embodiment, an example of the configuration of the light source device 100 in the case where the spontaneously emitted light 88 emitted from the first portion 82 of the light-emitting element 112 is detected by the light-receiving element 122 will be described.

[0140] Although the light emitting element 112 and the light receiving element 122 applicable to this embodiment are not particularly limited, here, as an example, a light source device 100 having a configuration in which the light emitting element 112 of the second embodiment and the light receiving element 122 of the fourth embodiment are combined is assumed. Note that the determination unit 130 is omitted from Figs. 21 and 22.

[0141] Laser light 84 is mainly emitted from first portion 82 of light emitting element 112, but this also contains a component of spontaneous emission 88. Therefore, it is possible to detect the spontaneous emission 88 contained in laser light 84 and detect the timing of laser oscillation based on the detected spontaneous emission 88.

[0142] 21 is an example of a light source device in which light emitted from a first portion 82 of a light-emitting element 112 is separated into laser light 84 and spontaneous emission light 88 using a wavelength filter 92, and the separated spontaneous emission light 88 is collected by a lens 94 and made incident on a light-receiving element 122. The wavelength filter 92 has optical properties of transmitting the laser light 84 and reflecting the spontaneous emission light 88, and it is preferable to use a so-called long-pass filter that reflects light with wavelengths shorter than a specific wavelength λco and transmits light with wavelengths longer than λco.

[0143] In this configuration example, since the lens 94 is used to collect light, it is possible to reduce the light receiving area of ​​the light receiving element 122 to obtain the same signal strength. Since the value of dark current is approximately proportional to the light receiving area, the S / N ratio can be increased by reducing the light receiving area. In addition, since a faster response is generally possible by reducing the light receiving area, it is also preferable from the perspective of responsiveness to reduce the light receiving area.

[0144] 22 is obtained by adding an optical fiber 96 between the lens 94 and the light receiving element 122 to the configuration example of Fig. 21. By configuring the light that has passed through the lens 94 to be guided to the light receiving element 122 using the optical fiber 96, the degree of freedom in arranging the light emitting element 112 and the light receiving element 122 can be greatly improved.

[0145] Although the present embodiment illustrates the case where the light-emitting unit 110 has one light-emitting element 112, similar to the second embodiment, the light-emitting unit 110 may have a plurality of light-emitting elements 112. In this case, the wavelength filter 92 and the lens 94 may be provided for each of the plurality of light-emitting elements 112, or may be provided for the plurality of light-emitting elements 112.

[0146] As described above, according to this embodiment, since the oscillation timing of the laser light is detected using spontaneous emission light, it is possible to improve the measurement accuracy of the oscillation timing of the laser light without reducing the light intensity of the laser light. Furthermore, by incorporating the light source device of this embodiment into a LiDAR system, it is possible to realize a LiDAR system with high ranging accuracy.

[0147] [Eighth embodiment] A distance measuring device according to an eighth embodiment of the present invention will be described with reference to Fig. 23. Components similar to those of the light source devices according to the first to seventh embodiments are given the same reference numerals, and descriptions thereof will be omitted or simplified. Fig. 23 is a block diagram showing a schematic configuration of the distance measuring device according to this embodiment.

[0148] A distance measuring device 200 according to this embodiment is a distance measuring device (LiDAR device) in which the light source device 100 according to any one of the first to seventh embodiments is applied to a light source section.

[0149] The distance measuring device 200 according to this embodiment can be configured with a control unit 210, a surface-emitting laser array driver 212, a surface-emitting laser array 214, an emission-side optical system 218, a reception-side optical system 220, an image sensor 222, and a distance data processing unit 224. The surface-emitting laser array 214 has an emission timing monitor unit 216.

[0150] The surface-emitting laser array 214 is configured by mounting the light-emitting unit 110 according to any one of the first to seventh embodiments in a package, and has a plurality of light-emitting elements 112 arranged in a two-dimensional array. The surface-emitting laser array 214 further includes an emission timing monitor unit 216. The emission timing monitor unit 216 corresponds to the emission timing monitor unit 120 according to the first to seventh embodiments. An electrical signal generated by the emission timing monitor unit 216 is supplied to a distance data processing unit 224. The surface-emitting laser array driver 212 is a driving unit that receives a drive signal from the control unit 210, generates a drive current for oscillating the surface-emitting laser array 214, and outputs the drive current to the surface-emitting laser array 214. The surface-emitting laser array 214 and the surface-emitting laser array driver 212 may be a single device.

[0151] The light-emitting side optical system 218 is an optical system that emits laser light generated by the surface-emitting laser array 214 toward the range to be measured. The light-receiving side optical system 220 is an optical system that guides laser light reflected by the measurement object 1000 to the image sensor 222. Although the light-emitting side optical system 218 and the light-receiving side optical system 220 are represented by a single convex lens-shaped member in Fig. 23, they may be composed of a single convex lens-shaped member or a lens group combining multiple lenses.

[0152] The image sensor 222 is a photoelectric conversion device in which a plurality of pixels, each including a photoelectric conversion unit, are arranged in a two-dimensional array, and is a light-receiving device that outputs an electrical signal in response to incident light. The image sensor 222 may be an imaging device such as a CMOS image sensor or an image sensor in which SPAD (Single Photon Avalanche Diode) photosensors are arranged in a two-dimensional array. Note that when configured to separate the spontaneous emission light 88 from the light emitted from the first portion 82 of the light-emitting element 112 as in the seventh embodiment, the image sensor 222 may also have the function of the light emission timing monitor unit 216.

[0153] Distance data processing unit 224 functions as a distance information acquisition unit that generates and outputs information relating to the distance to measurement object 1000 present in the distance measurement range based on electrical signals received from light emission timing monitor unit 216 and image sensor 222. Distance data processing unit 224 may have the function of determination unit 130 in the first to seventh embodiments. Note that distance data processing unit 224 only needs to be electrically connected to image sensor 222, and may be arranged in the same package as image sensor 222 or in a package separate from image sensor 222.

[0154] The control unit 210 is configured by an information processing device including a microcomputer and logic circuits, and functions as a central processing device that controls the operation of each unit and performs various calculation processes in the distance measuring device 200.

[0155] Next, the operation of the distance measuring device according to this embodiment will be described with reference to FIG. First, the control unit 210 outputs a drive signal to the surface-emitting laser array driver 212. The surface-emitting laser array driver 212 receives the drive signal from the control unit 210 and injects a current of a predetermined current value into the surface-emitting laser array 214. This causes the surface-emitting laser array 214 to oscillate, and laser light is output from the surface-emitting laser array 214. At this time, the pulse width of the light output from the surface-emitting laser array 214 is narrower than the pulse width of the injected current, as described above.

[0156] The laser light generated by the surface-emitting laser array 214 is emitted toward the distance measurement target range by the light-emitting side optical system 218. At this time, the spontaneous emission light 88 emitted from the surface-emitting laser array 214 is incident on the light-emission timing monitor unit 216. The light-emission timing monitor unit 216 generates an electrical signal in response to the incidence of the spontaneous emission light 88, and outputs it to the distance data processing unit 224. The distance data processing unit 224 detects the timing of laser oscillation in the surface-emitting laser array 214 based on the electrical signal received from the light-emission timing monitor unit 216.

[0157] Of the laser light irradiated onto the measurement object 1000 within the distance measurement range, the laser light reflected by the measurement object 1000 and incident on the light-receiving side optical system 220 is guided by the light-receiving side optical system 220 to the image sensor 222. Each pixel of the image sensor 222 generates an electrical signal pulse according to the timing at which the laser light is incident. The electrical signal pulse generated by the image sensor 222 is input to the distance data processing unit 224.

[0158] The distance data processing unit 224 generates information about the distance to the measurement object 1000 along the light propagation direction, based on the detected laser oscillation timing and the reception timing of the electrical signal pulse output from the image sensor 222. By calculating the distance information based on the electrical signal pulse output from each pixel of the image sensor 222, three-dimensional information about the measurement object 1000 can be acquired.

[0159] By configuring the distance measuring device 200 in this way, even if the light emission timing of the surface emitting laser array 214 is shifted due to factors such as the ambient temperature, the distance measuring accuracy is not affected and high distance measuring accuracy can be maintained.

[0160] Next, the reason why the distance measuring device in this embodiment is configured as described above will be explained with reference to FIGS.

[0161] In a LiDAR system, the distance to an object is calculated based on the time difference between when a laser beam is emitted and when it is reflected by the object and returns. Therefore, to improve distance measurement accuracy, it is necessary to know with higher accuracy the timing at which the light-emitting pulse is generated in the light-emitting element 112. For example, if the time detection accuracy on the light-receiving side is about 50 ps, ​​it is preferable that the accuracy of the information on the pulse generation timing on the light-emitting side be less than 50 ps.

[0162] In typical VCSELs and LiDAR systems using them, a VCSEL driver generates a pulsed current to drive the VCSEL. Because the VCSEL emits light in response to the pulsed current waveform, the difference between the VCSEL's light emission timing and the rising edge of the pulsed current generated by the VCSEL driver is small, and this time difference does not change significantly due to fluctuations in environmental temperature, etc. This is because the VCSEL is designed to emit light in response to the injected current value. Therefore, it is possible to accurately estimate the time from the generation timing of the current pulse in the driver to the VCSEL's light emission timing.

[0163] On the other hand, the inventors have discovered for the first time that when the time difference between the generation timing of the current pulse and the generation timing of the light pulse is estimated using the above-mentioned method, the ranging accuracy may decrease in a LiDAR system using the light-emitting element 112 of the first to seventh embodiments.

[0164] In the light emitting device 112 of the first to seventh embodiments, carriers are accumulated in the active layer 20, and after the start of laser oscillation, the accumulated carriers are converted into light to generate an optical pulse. That is, for a predetermined time until carriers are accumulated in the active layer 20, the current injected into the light emitting device 112 is used to accumulate carriers in the active layer 20. Then, laser oscillation of the light emitting device 112 is delayed for a predetermined time until carriers are accumulated in the active layer 20.

[0165] The timing of laser oscillation in the semiconductor light-emitting device according to the first to seventh embodiments is determined by the structure of the semiconductor light-emitting device and the physical parameters of the materials constituting each part. Therefore, even if the current waveform generated by the surface-emitting laser array driver 212 is the same, the time difference between the start of driving and the start of laser oscillation changes due to changes in the environmental temperature and changes in the physical parameters over time. This time difference may exceed approximately 50 ps, ​​which is a typical time detection accuracy on the light-receiving side.

[0166] 24 and 25 are graphs showing the results of calculations of changes in optical waveform due to changes in environmental temperature and changes in physical parameters over time. Fig. 24 shows the calculation results for a general VCSEL, and Fig. 25 shows the calculation results for the light-emitting elements of the first to seventh embodiments.

[0167] 24 and 25 show enlarged optical waveforms immediately after the start of oscillation, assuming a transparent carrier density at room temperature and a transparent carrier density at a temperature 50° C. higher than room temperature. In both figures, the characteristic in which oscillation starts first is the case in which the transparent carrier density is assumed at room temperature, and the characteristic in which oscillation starts later is the case in which the transparent carrier density is assumed at a temperature 50° C. higher than room temperature.

[0168] In a typical VCSEL, as shown in Figure 24, the time difference between the peak time of the optical pulse when the transparent carrier density is assumed to be at room temperature and the peak time of the optical pulse when the transparent carrier density is assumed to be 50°C higher than room temperature is 13 ps.

[0169] On the other hand, in the light-emitting element 112 of the above embodiment, the time difference between the peak time of the light pulse when the transparent carrier density is assumed to be at room temperature and the peak time of the light pulse when the transparent carrier density is assumed to be 50° C. higher than room temperature is 70 ps, ​​as shown in Fig. 25. The time difference from the timing at which current injection into the light-emitting element 112 starts to the timing at which the light output reaches its maximum peak value can vary, for example, within a range of 50 ps or more and 1 ns or less, due to changes in the environmental temperature, etc.

[0170] As described above, in the light-emitting element 112 of the above embodiment, changes in the physical properties have a large effect on changes in the oscillation timing, and the amount of change in the oscillation timing may exceed approximately 50 ps, ​​which is a typical time detection accuracy on the light-receiving side.

[0171] From this perspective, in the distance measuring device 200 of this embodiment, the light emission timing of the surface-emitting laser array 214 is detected by the light emission timing monitor unit 216. Then, distance information is calculated using the light emission timing detected by the light emission timing monitor unit 216. Therefore, even if the light emission timing of the surface-emitting laser array 214 is shifted due to factors such as the ambient temperature, this does not affect the distance measurement accuracy of the distance measuring device 200, and high distance measurement accuracy can be maintained.

[0172] The distance measuring device 200 of this embodiment can be applied to, for example, a control device in the automotive field that controls a vehicle to avoid collision with another vehicle, or a control device that controls automatic driving by following another vehicle. The distance measuring device 200 of this embodiment can also be applied to other moving objects (moving devices) such as ships, aircraft, and industrial robots, as well as moving object detection systems. The distance measuring device 200 of this embodiment can be widely applied to devices that use information about objects recognized three-dimensionally, including distance information. These moving objects can be configured to include the distance measuring device of this embodiment and control means that controls the moving object based on the distance information acquired by the distance measuring device.

[0173] Furthermore, the three-dimensional information including depth that can be acquired by the distance measuring device 200 of this embodiment can also be used in an image capturing device, an image processing device, a display device, etc. For example, by using the three-dimensional information acquired by the distance measuring device 200 of this embodiment, it is possible to display a virtual object on an image of the real world without creating a sense of incongruity. Furthermore, by storing the three-dimensional information together with the image information, it is also possible to correct the blurring of the captured image after shooting.

[0174] As described above, according to this embodiment, a high-performance distance measuring device equipped with the light source device of the first to seventh embodiments can be realized.

[0175] [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.

[0176] In the first to seventh embodiments, GaAs, AlGaAs, and InGaAs are exemplified as semiconductor materials on which crystal growth is possible when a GaAs substrate is used as the semiconductor substrate 10, but the semiconductor substrate 10 is not limited to a GaAs substrate. For example, an InP substrate can also be used as the semiconductor substrate 10. Examples of semiconductor materials on which crystal growth is possible when a GaAs substrate is used as the semiconductor substrate 10 include InP, InGaAs, InGaP, and InGaAsP.

[0177] Furthermore, the DBR layer in the semiconductor light-emitting devices according to the first to seventh embodiments does not necessarily have to be made of a semiconductor material, and may be made of a material other than a semiconductor material. In this case, too, by configuring it to have the same functions as those of the first and second embodiments, the same effects as those of the present embodiment can be achieved.

[0178] It should be noted that the above-described embodiments are merely examples of specific embodiments for carrying out the present invention, and the technical scope of the present invention should not be construed as being limited by these embodiments. In other words, the present invention can be carried out in various forms without departing from its technical concept or main features. [Explanation of symbols]

[0179] 100...Light source device 110...Light emitting part 112...light-emitting element 120...Light emission timing monitor 122...Photodetector 124...Light receiving section 130...judgment section 200…Distance measuring device

Claims

1. a light emitting device having a first reflecting mirror, a second reflecting mirror, and a cavity spacer portion including an active layer provided between the first reflecting mirror and the second reflecting mirror, and emitting a first light which is a laser beam and a second light which is a spontaneous emission light; a light receiving element for detecting the amount of the second light; a determination unit that detects the timing at which the first light is oscillated based on the fact that the amount of the second light detected by the light receiving element increases for a certain period of time from the start of current injection into the light emitting element and then decreases; A light source device comprising:

2. the first light is emitted from a first portion of the light-emitting element; The second light is emitted from a second portion of the light-emitting element that is different from the first portion.

2. The light source device according to claim 1.

3. The light-emitting element emits the first light in a first direction and the second light in a second direction intersecting the first direction.

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

4. The optical fiber further includes a wavelength filter that separates the third light emitted from the light emitting element into the first light and the second light.

2. The light source device according to claim 1.

5. The wavelength filter is a long-pass filter that transmits light on the wavelength side longer than a wavelength λco and reflects light on the wavelength side shorter than the wavelength λco, and the wavelength λco has the following relationship, where λc is a resonance wavelength of the first light: λco < λc-5 [nm] 5. The light source device according to claim 4.

6. The wavelength filter is a long-pass filter that transmits light on the wavelength side longer than the wavelength λco and reflects light on the wavelength side shorter than the wavelength λco, and the wavelength λco has the following relationship, where λc is a resonance wavelength of the first light: λco ≦ λc-30 [nm] 5. The light source device according to claim 4.

7. the light-emitting element is configured to emit the first 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; The maximum peak value is three times or more the stable value.

7. The light source device according to claim 1, wherein the light source device is a light source unit.

8. The determination unit determines that the first light has oscillated when a differential value of the amount of the second light with respect to time becomes equal to or less than a predetermined threshold.

8. The light source device according to claim 1, wherein the light source device is a light source unit.

9. The determination unit determines that the first light has oscillated at a timing when a second-order differential value with respect to time of the amount of light of the second light reaches a peak.

8. The light source device according to claim 1, wherein the light source device is a light source unit.

10. The determination unit predicts the timing at which the first light will oscillate based on a lookup table that represents a relationship between a delay time of a peak time of the first light relative to a peak time of the second light and environmental information.

8. The light source device according to claim 1, wherein the light source device is a light source unit.

11. The light-emitting element further includes a light-shielding film between the light-emitting element and the light-receiving element, the light-shielding film preventing the first light from entering the light-receiving element.

11. The light source device according to claim 1.

12. The light-emitting element further includes a light-shielding film between the light-emitting element and the light-receiving element, the light-shielding film preventing the first light from entering the light-receiving element.

11. The light source device according to claim 1.

13. The optical fiber further includes a wavelength filter between the light emitting element and the light receiving element that does not transmit the wavelength range of the first light.

11. The light source device according to claim 1.

14. the light-emitting device further includes a saturable absorbing layer between the first reflecting mirror and the second reflecting mirror; the active layer is configured by sandwiching an InGaAs well layer between AlGaAs barrier layers, The Al composition of the AlGaAs barrier layer is 0 to 30%.

14. The light source device according to claim 1, wherein the light source device is a light source unit.

15. The light emitting element is a vertical cavity surface emitting laser element.

15. The light source device according to claim 1, wherein the light source device is a light source unit.

16. The light receiving element has a light receiving portion having the same configuration as the active layer.

16. The light source device according to claim 1, wherein the light source device is a light source unit.

17. The following relationship holds: L is the distance between the light-emitting portion of the light-emitting element and the light-receiving portion of the light-receiving element, P is the total amount of the second light emitted from the light-emitting element, S is the area of ​​the light-receiving portion, Q is the sensitivity of the light-receiving portion, and Da is the dark current of the light-emitting element. P×(S / 4πL2)×Q > Da 17. The light source device according to claim 1.

18. A light source device according to any one of claims 1 to 17; a light receiving device that receives light emitted from the light source device and reflected by a measurement object; a distance information acquiring unit that acquires information about the distance to the object to be measured based on a time difference between a timing at which the first light is emitted from the light source device and a timing at which the light is received by the light receiving device; A distance measuring device comprising:

19. A mobile object, a distance measuring device according to claim 18; a control means for controlling the moving object based on information about the distance acquired by the distance measuring device; A moving object characterized by having:

Images