Light emitting device and rangefinder

Abstract

To reduce the temperature dependence of a light output characteristics in a surface-emitting light emitting device with a saturable absorption layer.SOLUTION: A light emitting device has a resonator comprising a first reflector and a second reflector arranged on a semiconductor substrate, and a resonator spacer section positioned between the first and second reflectors and comprising an active layer and a saturable absorption layer. The first reflector, resonator spacer section, and second reflector are stacked in this order on the semiconductor substrate, the active layer comprises an asymmetric quantum well structure containing a plurality of types of quantum wells with different wavelengths corresponding to the bandgap, and the gain peak wavelength of the active layer is shorter than the laser oscillation wavelength of the resonator.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Vertical cavity surface emitting lasers (VCSELs) are being developed as light sources for LiDAR (Light Detection and Ranging) systems, 3D (Dimension) sensors, etc. Patent Document 1 describes a VCSEL configured to generate optical pulses with short optical pulse widths and high peak values ​​by providing a saturable absorption layer in the laser resonator section. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-176886 Summary of the Invention [Problem to be solved by the invention]

[0004] The VCSEL described in Patent Document 1 has the advantage of being able to output extremely short, high-peak pulsed light of about several hundred picoseconds at the start of oscillation, and when applied to a light source device in a LiDAR system, for example, it is expected to improve ranging distance and ranging accuracy. However, VCSELs with saturable absorbing layers have a greater wavelength dependency on temperature than VCSELs without a saturable absorbing layer, which could potentially eliminate the benefits of applying them to LiDAR systems. [Means for solving the problem]

[0005] An object of the present disclosure is to provide a technique for reducing the temperature dependency of the light output characteristics in a surface-emitting light-emitting device having a saturable absorbing layer.

[0006] According to one disclosure of the present specification, there is provided a light-emitting device including: a resonator arranged on a semiconductor substrate and including a first reflecting mirror and a second reflecting mirror; and a resonator spacer portion arranged between the first reflecting mirror and the second reflecting mirror and including an active layer and a saturable absorbing layer, wherein the first reflecting mirror, the resonator spacer portion, and the second reflecting mirror are stacked in this order on the semiconductor substrate; the active layer has an asymmetric quantum well structure including multiple types of quantum wells with different wavelengths corresponding to bandgaps; and the gain peak wavelength of the active layer is shorter than the laser oscillation wavelength of the resonator.

[0007] Furthermore, according to another disclosure of the present specification, there is provided a light emitting device including: a resonator arranged on a semiconductor substrate and including a first reflecting mirror and a second reflecting mirror; and a resonator spacer portion arranged between the first reflecting mirror and the second reflecting mirror and including an active layer and a saturable absorbing layer, wherein the first reflecting mirror, the resonator spacer portion, and the second reflecting mirror are stacked in this order on the semiconductor substrate; the active layer has an asymmetric quantum well structure including multiple types of quantum wells with different wavelengths corresponding to bandgaps; and the gain peak wavelength of the active layer is set so that the gain of the active layer at the laser oscillation wavelength of the resonator becomes a first value at a first temperature and becomes a second value greater than the first value at a second temperature higher than the first temperature.

[0008] Furthermore, according to yet another disclosure of the present specification, there is provided a light-emitting device including: a resonator arranged on a semiconductor substrate and including a first reflecting mirror and a second reflecting mirror; and a resonator spacer portion arranged between the first reflecting mirror and the second reflecting mirror and including an active layer and a saturable absorbing layer, wherein the first reflecting mirror, the resonator spacer portion, and the second reflecting mirror are stacked in this order on the semiconductor substrate; a gain peak wavelength of the active layer is shorter than a laser oscillation wavelength of the resonator; and the saturable absorbing layer includes a quantum well whose wavelength corresponding to a band gap is longer than the laser oscillation wavelength.

[0009] Furthermore, according to yet another disclosure of the present specification, there is provided a light-emitting device including: a resonator arranged on a semiconductor substrate and including a first reflecting mirror and a second reflecting mirror; and a resonator spacer portion arranged between the first reflecting mirror and the second reflecting mirror and including an active layer and a saturable absorbing layer, wherein the first reflecting mirror, the resonator spacer portion, and the second reflecting mirror are stacked in this order on the semiconductor substrate; a gain peak wavelength of the active layer is set so that a gain of the active layer at a laser oscillation wavelength of the resonator becomes a first value at a first temperature and becomes a second value greater than the first value at a second temperature higher than the first temperature; and the saturable absorbing layer includes a quantum well whose wavelength corresponding to a band gap is longer than the laser oscillation wavelength. [Effects of the Invention]

[0010] According to the present disclosure, in a surface-emitting light-emitting device having a saturable absorbing layer, the temperature dependency of the light output characteristics can be reduced. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic cross-sectional view showing an example of the configuration of a light emitting device according to a first embodiment. [Figure 2A] 1 is a graph showing the optical output characteristics at room temperature of a VCSEL element having a saturable absorbing layer. [Figure 2B] 1 is a graph showing the optical output characteristics at high temperatures of a VCSEL element having a saturable absorbing layer. [Figure 3A] 1 is a graph showing the relationship between the gain spectrum of an active layer at room temperature, the optical absorption spectrum of a saturable absorbing layer, and the laser oscillation wavelength in a typical light emitting device. [Figure 3B] 1 is a graph showing the relationship between the gain spectrum of an active layer at high temperatures, the optical absorption spectrum of a saturable absorbing layer, and the laser oscillation wavelength in a typical light emitting device. [Figure 4A] 4 is a graph showing the relationship between the gain spectrum of the active layer at room temperature, the optical absorption spectrum of the saturable absorbing layer, and the laser oscillation wavelength in the light emitting device according to the first embodiment. [Figure 4B] 4 is a graph showing the relationship between the gain spectrum of the active layer at high temperatures, the optical absorption spectrum of the saturable absorbing layer, and the laser oscillation wavelength in the light emitting device according to the first embodiment. [Figure 5] 4 is a graph showing the results of calculating the gain spectrum of the active layer in the light emitting device according to the first embodiment. [Figure 6] 4 is a graph showing the results of calculation of the light absorption spectrum of the saturable absorbing layer in the light emitting device according to the first embodiment. [Figure 7] 10 is a graph showing the results of calculating the gain spectrum of an active layer in a light emitting device according to a comparative example. [Figure 8] FIG. 4 is a diagram showing changes in light output characteristics with temperature in the light emitting device according to the first embodiment. [Figure 9] 10 is a graph showing the results of calculation of the light absorption spectrum of the saturable absorbing layer in the light emitting device according to the second embodiment. [Figure 10] 10 is a graph showing the results of calculation of the optical absorption spectrum and its differential spectrum of the saturable absorbing layer in the light emitting device according to the second embodiment. [Figure 11] 10 is a graph showing the results of calculating the gain spectrum of the active layer in the light emitting device according to the third embodiment. [Figure 12] FIG. 11 is a diagram showing changes in light output characteristics with temperature in the light emitting device according to the third embodiment. [Figure 13] FIG. 10 is a perspective view showing a light emitting device according to a fourth embodiment. [Figure 14] FIG. 10 is a top view of a light emitting device according to a fourth embodiment. [Figure 15] FIG. 10 is a cross-sectional view showing a schematic configuration of a light emitting device according to a fifth embodiment. [Figure 16] FIG. 10 is a block diagram showing a schematic configuration of a distance measuring device according to a sixth embodiment. [Figure 17] FIG. 13 is a block diagram showing a schematic configuration of a distance measuring device according to a seventh embodiment. [Figure 18]FIG. 13 is a schematic cross-sectional view showing an example of the configuration of a surface-emitting laser array in a distance measuring device according to a seventh embodiment. [Figure 19A] FIG. 13 is a block diagram showing an example of the configuration of a device according to an eighth embodiment. [Figure 19B] FIG. 13 is a block diagram showing an example of the configuration of a moving body according to the eighth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] [First embodiment] The light emitting device according to the first embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic cross-sectional view showing an example of the configuration of the light emitting device according to this embodiment.

[0013] The light-emitting device 100 according to this embodiment is a vertical-cavity surface-emitting laser (VCSEL) having a distributed Bragg reflector (DBR). As shown in FIG. 1 , the light-emitting device 100 may include a semiconductor substrate 10, a lower DBR layer 12, an undoped spacer portion 14, a resonator portion 18, an upper DBR layer 28, electrodes 40 and 42, and a protective film 44. The lower DBR layer 12 is disposed on the semiconductor substrate 10. The undoped spacer portion 14 is disposed on the lower DBR layer 12. The resonator portion 18 is disposed on the undoped spacer portion 14. The upper DBR layer 28 is disposed on the resonator portion 18. The layers (the undoped spacer portion 14 and the resonator portion 18) located between the lower DBR layer 12 and the upper DBR layer 28 form the resonator spacer portion.

[0014] A saturable absorbing layer 16 is provided in the undoped spacer portion 14. The resonator portion 18 is composed of an n-type layer 20 provided on the undoped spacer portion 14, an undoped spacer portion 22 provided on the n-type layer 20, and a p-type layer 26 provided on the undoped spacer portion 22. An active layer 24 is provided in the undoped spacer portion 22. A current confinement layer 38 is provided in the upper DBR layer 28.

[0015] The undoped spacer portion 22, the p-type layer 26, and the upper DBR layer 28 are processed into a mesa shape. An electrode 40 electrically connected to the n-type layer 20 is provided on the n-type layer 20 exposed by processing the undoped spacer portion 22, the p-type layer 26, and the upper DBR layer 28 into a mesa shape. An electrode 42 electrically connected to the upper DBR layer 28 is provided on the upper surface of the n-type layer 20, excluding at least a portion of the surfaces of the electrodes 40 and 42, and on the side and upper surfaces of the mesa.

[0016] 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 has a central wavelength of 940 nm, and the lower DBR layer 12 has a central wavelength of 940 nm.

[0017] The saturable absorbing layer 16 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 14 may be formed of undoped GaAs layers.

[0018] The resonator section 18 is formed by a pin junction consisting of an n-type layer 20, an undoped spacer section 22, and a p-type layer 26. The active layer 24 disposed in the undoped spacer section 22 may be formed by a multiple quantum well 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 n-type layer 20 may be formed by an n-type AlGaAs layer, the p-type layer 26 by a p-type AlGaAs layer, and the remaining portions of the undoped spacer section 22 by undoped GaAs layers.

[0019] In the light emitting device 100 of this embodiment, the active layer 24 is designed so that the gain peak wavelength at room temperature is positioned on the shorter wavelength side than the laser oscillation wavelength at room temperature. The reason for designing the active layer 24 in this way will be explained below.

[0020] VCSEL elements with saturable absorbing layers have the advantage of being able to output extremely short, high-peak pulsed light of about several hundred picoseconds at the start of oscillation, and when applied to a light source device for a LiDAR system, for example, they are expected to improve ranging distance and ranging accuracy. However, after extensive research by the present inventors into VCSEL elements with saturable absorbing layers, they found that light emission characteristics such as the timing of light pulse generation and peak light intensity are significantly affected by temperature.

[0021] 2A and 2B are graphs showing the optical output characteristics of a VCSEL device having a saturable absorbing layer. Fig. 2A shows the optical output characteristics at room temperature (20°C), and Fig. 2B shows the optical output characteristics at a high temperature (80°C). As shown in Figs. 2A and 2B, as the temperature rises from 20°C to 80°C, the timing of the optical pulse generation is delayed by approximately 0.9 nsec. Furthermore, as the temperature rises from 20°C to 80°C, the peak optical intensity decreases by approximately 30%. The present inventors speculate that the cause of this degradation in the optical output characteristics is as follows.

[0022] The gain spectrum of the active layer, the optical absorption spectrum of the saturable absorbing layer, and the laser oscillation wavelength all tend to shift toward longer wavelengths with increasing temperature. While the amount of shift toward longer wavelengths varies depending on the materials used in the light-emitting device, the gain spectrum of the active layer and the optical absorption spectrum of the saturable absorbing layer in a light-emitting device constructed using the above-mentioned materials all shift toward longer wavelengths at a rate of approximately 0.4 nm / K. The laser oscillation wavelength also shifts toward longer wavelengths with increasing temperature, but the rate is approximately 0.07 nm / K, which is smaller than the temperature dependence of the gain spectrum of the active layer and the optical absorption spectrum of the saturable absorbing layer. As a result, changes in temperature result in changes in the correlation between the gain spectrum of the active layer, the optical absorption spectrum of the saturable absorbing layer, and the laser oscillation wavelength. The temperature dependence of the gain spectrum of the active layer and the optical absorption spectrum of the saturable absorbing layer is determined by the physical properties of the semiconductor materials used in the light-emitting device, making it difficult to directly control these.

[0023] 3A and 3B are graphs showing the relationship between the gain spectrum of the active layer, the optical absorption spectrum of the saturable absorbing layer, and the laser oscillation wavelength in a typical light-emitting device. Fig. 3A shows the characteristics at room temperature, and Fig. 3B shows the characteristics at high temperature. In each figure, the dashed-dotted line shows the gain spectrum of the active layer, the dashed-two-dotted line shows the optical absorption spectrum of the saturable absorbing layer, and the dotted line shows the laser oscillation wavelength.

[0024] In a typical VCSEL device, the emission wavelength of the active layer is designed so that the gain peak wavelength is located near the laser oscillation wavelength, as shown in Figure 3A. When the temperature of this VCSEL device increases, the gain spectrum of the active layer and the optical absorption spectrum of the saturable absorbing layer shift to longer wavelengths relative to the laser oscillation wavelength, as shown in Figure 3B.

[0025] When the gain spectrum of the active layer shifts to a longer wavelength relative to the laser oscillation wavelength, causing the laser oscillation wavelength to be positioned shorter than the gain peak wavelength, the gain at the laser oscillation wavelength decreases compared to room temperature, as shown in Figure 3B. Furthermore, when the optical absorption spectrum of the saturable absorbing layer shifts to a longer wavelength relative to the laser oscillation wavelength, optical absorption at the laser oscillation wavelength increases. Both of these phenomena result in changes that make laser oscillation more difficult, and it is believed that these combined effects cause a delay in the timing of optical pulse generation and a decrease in light emission characteristics such as peak optical intensity.

[0026] From this perspective, in the light-emitting device of this embodiment, the gain peak wavelength of the active layer 24 is designed so that the direction of change in the gain of the active layer 24 with temperature and the direction of change in the optical absorption of the saturable absorbing layer 16 are opposite to each other. From one perspective, this technique can be designed so that the gain peak wavelength of the active layer 24 at room temperature is shorter than the laser oscillation wavelength at room temperature. From another perspective, the gain peak wavelength of the active layer 24 can be designed so that the gain at the laser oscillation wavelength at a first temperature is a first value and the gain at the laser oscillation wavelength at a second temperature higher than the first temperature is a second value greater than the first value. Here, the first temperature can be, for example, room temperature, and the second temperature can be, for example, the highest ambient temperature expected during operation.

[0027] 4A and 4B are graphs showing the relationship between the gain spectrum of the active layer, the optical absorption spectrum of the saturable absorbing layer, and the laser oscillation wavelength in the light-emitting device of this embodiment. Fig. 4A shows the characteristics at room temperature, and Fig. 4B shows the characteristics at high temperature.

[0028] As shown in Figures 3A and 3B, the gain of the active layer 24 decreases toward shorter wavelengths from the gain peak wavelength and toward longer wavelengths from the gain peak wavelength. Therefore, in the light-emitting device of this embodiment, the active layer 24 is designed so that the gain peak wavelength at room temperature is shorter than the laser oscillation wavelength at room temperature, as shown in Figure 4A. By configuring it in this way, even if the gain spectrum of the active layer 24 shifts toward longer wavelengths relative to the laser oscillation wavelength at high temperatures, the gain at the laser oscillation wavelength does not decrease, but can actually increase, as shown in Figure 4B.

[0029] 3A and 3B, the optical absorption in the saturable absorbing layer 16 increases toward shorter wavelengths. Therefore, when the optical absorption spectrum shifts toward longer wavelengths relative to the laser oscillation wavelength at high temperatures, the optical absorption in the saturable absorbing layer 16 also increases. However, by designing the active layer 24 so that the gain peak wavelength at room temperature is shorter than the laser oscillation wavelength at room temperature, at least a portion of the increase in optical absorption by the saturable absorbing layer 16 can be offset by an increase in gain. This reduces the deviation in the correlation between the gain spectrum and the optical absorption spectrum and the laser oscillation wavelength that occurs with temperature changes, and ultimately suppresses changes in the light-emitting characteristics of the light-emitting device that occur with temperature changes.

[0030] The gain peak wavelength of the active layer 24 at high temperatures does not necessarily have to be shorter than the laser oscillation wavelength at high temperatures. As long as the gain at high temperatures exceeds the gain at room temperature, the increased gain can offset at least a portion of the increase in light absorption by the saturable absorbing layer 16, thereby achieving the effects of this embodiment. That is, as described above, it is sufficient to adjust the gain peak wavelength of the active layer 24 so that the gain at the laser oscillation wavelength at a first temperature is a first value and the gain at the laser oscillation wavelength at a second temperature higher than the first temperature is a second value greater than the first value.

[0031] In a typical VCSEL device, if optimizing its performance at high temperatures is a priority, it is conceivable to shift the gain peak wavelength of the active layer to a wavelength shorter than the lasing wavelength. This design can reduce the threshold current and improve optical output at high temperatures. However, in the case of a VCSEL device with a saturable absorbing layer, as mentioned above, as the temperature rises, not only the gain spectrum of the active layer but also the optical absorption spectrum of the saturable absorbing layer shifts to a longer wavelength. Therefore, shifting the gain peak wavelength of the active layer to a wavelength shorter than the lasing wavelength does not necessarily improve the optical output characteristics.

[0032] This disclosure is not intended to improve optical output characteristics, but rather to reduce the temperature dependence of the timing at which short optical pulses are generated at the start of oscillation. This disclosure is based on a design concept that shifts the gain peak wavelength of the active layer to a shorter wavelength than the laser oscillation wavelength to offset the increase in the absorption coefficient of the saturable absorbing layer due to temperature rise, which is not a common design concept for VCSEL elements with a saturable absorbing layer. In LiDAR systems, stabilizing the timing of the optical pulse reflected from the target is important because it directly affects ranging accuracy. While the optical intensity of the optical pulse must be above the minimum level at which the timing can be detected, the need to stabilize the optical intensity within a certain range is significantly less than in VCSELs used in optical communication systems and electrophotography systems, since all that is required is to know the timing at which the light is detected. In response to the requirements of such LiDAR systems, this disclosure is designed to shift the gain peak of the active layer to a shorter wavelength than the oscillation wavelength in order to reduce the temperature dependence of the optical pulse generation timing, rather than stabilizing the temperature dependence of the optical intensity.

[0033] 5 is a graph showing the results of calculating the gain spectrum of the active layer 24 in the light-emitting device according to this embodiment. This is a calculation example in which the gain peak wavelength of the active layer 24 at room temperature is set to 920 nm, which is 20 nm shorter than the laser oscillation wavelength of 940 nm. The vertical axis represents the carrier concentration of 3.2×10 18 cm -3 The figure shows the average gain coefficient of a three-layer quantum well at 1000 MHz. The horizontal axis represents wavelength.

[0034] FIG. 6 is a graph showing the calculated optical absorption spectrum of the saturable absorbing layer 16 in the light-emitting device according to this embodiment. This graph shows a calculation example in which the wavelength corresponding to the bandgap of the quantum well constituting the saturable absorbing layer 16 is set to 940 nm, the same as the laser oscillation wavelength. Here, the quantum well bandgap refers to the energy difference between the ground states of the conductor and valence bands within the quantum well. The quantum well bandgap Eg of the quantum well constituting the saturable absorbing layer 16 in this case is 1.319 eV. The vertical axis represents the average absorption coefficient of the three quantum wells. The horizontal axis represents the wavelength. In FIG. 6, the absorption coefficient is shown as a negative value to visually facilitate understanding of the relationship with the gain coefficient of the active layer 24. The larger the absolute value of the absorption coefficient, the greater the optical absorption.

[0035] 7 shows, as a comparative example, a calculation example in which the gain peak wavelength of the active layer 24 at room temperature is set to 940 nm, the same as the laser oscillation wavelength. In the calculation, the active layer 24 is assumed to have a multiple quantum well structure including three quantum well layers, as in this embodiment. The vertical axis represents the carrier concentration of 3.2×10 18 cm -3 The figure shows the average gain coefficient of a three-layer quantum well at 1000 MHz. The horizontal axis represents wavelength.

[0036] 5 to 7, let us consider a case where the temperature rises from 25°C to 85°C. This temperature difference causes a difference of about 20 nm ((0.4 nm / K - 0.07 nm / K) x 60°C = 19.8 nm) between the wavelength shift of the gain spectrum and the optical absorption spectrum and the wavelength shift of the laser oscillation wavelength. The changes in the gain coefficient of the active layer 24 and the absorption coefficient of the saturable absorbing layer 16 that accompany this 20 nm wavelength shift of the gain spectrum and the optical absorption spectrum are summarized in Figure 8.

[0037] 8, in the comparative example, as the temperature rises, the gain of the active layer 24 decreases and the optical absorption of the saturable absorbing layer 16 increases, and as a whole, the change in the optical output characteristics with a change in temperature is large. In contrast, in the light-emitting device (example) of this embodiment, the gain of the active layer 24 can be increased with an increase in temperature, and as a whole, the change in the optical output characteristics with a change in temperature can be reduced more than in the comparative example.

[0038] As described above, according to this embodiment, in a VCSEL element having a saturable absorbing layer, the gain peak wavelength of the active layer is set to be shorter than the laser oscillation wavelength of the resonator, thereby reducing the temperature dependence of the optical output characteristics.

[0039] As mentioned above, the gain peak wavelength of the active layer 24 at high temperatures does not necessarily have to be shorter than the laser oscillation wavelength at high temperatures. That is, as long as the gain at high temperatures exceeds the gain at room temperature, at least a portion of the increase in optical absorption by the saturable absorbing layer 16 can be offset by the increased gain, thereby achieving the effects of this embodiment. That is, the lower limit of the gain peak wavelength of the active layer 24 can be a wavelength at which the gain at that time is equal to the gain when the temperature rises from 25°C to 85°C, i.e., the wavelength shift is approximately 20 nm ((0.4 nm / K - 0.07 nm / K) x 60°C = 19.8 nm). The gain peak wavelength at the wavelength shift of 20 nm is the long-wavelength limit of the gain peak wavelength of the active layer 24. In FIG. 5, the gain is the same at wavelengths 10 nm shorter and 10 nm longer than the gain peak wavelength. Therefore, in this case, the wavelength 10 nm longer than the gain peak wavelength can be used as the laser oscillation wavelength. The lower limit of the amount of shift of the gain peak wavelength to the shorter wavelength side is preferably 10 nm, although this depends on the temperature range used.

[0040] [Second embodiment] The light emitting device according to the second embodiment will be described with reference to Figures 9 and 10. Components similar to those in the light emitting device according to the first embodiment are given the same reference numerals, and descriptions thereof will be omitted or simplified.

[0041] The light emitting device according to this embodiment is similar to the light emitting device according to the first embodiment except for the wavelength corresponding to the band gap of the quantum well constituting the saturable absorbing layer 16. That is, in the light emitting device of the first embodiment, the wavelength corresponding to the band gap of the quantum well constituting the saturable absorbing layer 16 is set to the same wavelength as the laser oscillation wavelength. In contrast, in the light emitting device of this embodiment, the wavelength corresponding to the band gap of the quantum well constituting the saturable absorbing layer 16 is set to a wavelength longer than the laser oscillation wavelength.

[0042] FIG. 9 is a graph showing the results of calculating the optical absorption spectrum of the saturable absorbing layer 16. In the calculation, a multiple quantum well structure including three quantum well layers was assumed as the saturable absorbing layer 16, as in the first embodiment. In FIG. 9 , the dashed line represents a calculation example (Example 1) in which the wavelength corresponding to the bandgap of the quantum well constituting the saturable absorbing layer 16 is set to 940 nm, the same as the laser oscillation wavelength, and corresponds to the configuration of the first embodiment. The solid line represents a calculation example (Example 2) in which the wavelength corresponding to the bandgap of the quantum well constituting the saturable absorbing layer 16 is set to 955 nm, which is longer than the laser oscillation wavelength, and corresponds to the configuration of this embodiment. The bandgap Eg of the quantum well constituting the saturable absorbing layer 16 in this case is 1.298 eV. The vertical axis represents the average absorption coefficient of the three quantum well layers. The horizontal axis represents the wavelength.

[0043] 9, by shifting the wavelength corresponding to the band gap of the quantum well constituting the saturable absorbing layer 16 to the long wavelength side, the optical absorption spectrum of the saturable absorbing layer 16 also shifts to the long wavelength side. As a result, the change in the absorption coefficient of the saturable absorbing layer 16 in the wavelength range of 920 nm to 940 nm (i.e., the range of 920 nm to 940 nm) is smaller in Example 2 than in Example 1. Specifically, the change in the absorption coefficient of the saturable absorbing layer 16 in the wavelength range of 920 nm to 940 nm is 2468 cm in Example 1. -1 ], whereas in Example 2 it was 1527 [cm -1]. This means that the temperature dependency of the optical absorption of the saturable absorbing layer 16 at the laser oscillation wavelength can be reduced by shifting the wavelength corresponding to the band gap of the quantum well structure constituting the saturable absorbing layer 16 to the longer wavelength side. Therefore, according to the configuration of this embodiment, the change in the optical output characteristics due to the change in temperature can be further reduced compared to the first embodiment.

[0044] Fig. 10 shows the optical absorption spectrum and its differential spectrum (slope) of the saturable absorbing layer of Fig. 9. In the differential spectrum, a maximum point of the slope exists near the wavelength corresponding to the band gap, and the slope becomes smaller toward the shorter wavelength side near a wavelength of 940 nm, which is the laser oscillation wavelength of Example 2.

[0045] The change in the absorption coefficient with temperature of the saturable absorbing layer 16, which is the subject of the present disclosure, becomes small near the wavelength of 922 nm where the slope is at its minimum. However, because an actual device is not used only near a specific temperature point, it is required that the characteristics be stable over a certain temperature range. Therefore, one suitable range for the laser oscillation wavelength is a range in which the slope of the absorption coefficient is small, that is, a value equal to or less than the midpoint between the peak near the wavelength corresponding to the band gap and the minimum value near 922 nm. Because the temperature range in which lasers are applied in the majority of cases includes room temperature, it is preferable that the laser oscillation wavelength at room temperature be within the range in which the slope of the absorption coefficient is small.

[0046] 10, the preferred range of the laser oscillation wavelength at room temperature is 907 nm to 941 nm, and more preferably 922 nm to 941 nm, which has a margin on the short wavelength side in consideration of temperature shift at high temperatures, etc. In Example 2, the wavelength corresponding to the band gap of the saturable absorbing layer 16 is 955 nm, so the preferred range of the laser oscillation wavelength at room temperature is 14 nm to 48 nm shorter than the wavelength corresponding to the band gap of the saturable absorbing layer 16. More preferably, the preferred range of the laser oscillation wavelength at room temperature is 14 nm to 33 nm shorter than the wavelength corresponding to the band gap of the saturable absorbing layer 16. In addition, the preferred wavelength range can also be expressed in terms of the difference in photon energy corresponding to each wavelength.

[0047] Furthermore, when comparing the absorption coefficients of the saturable absorbing layer 16 at the same wavelength, the absorption coefficient in Example 1 is smaller than that in Example 2. This means that even if the absorption coefficient of the saturable absorbing layer 16 in the configuration of this embodiment is reduced to the same level as in Example 1, optical output characteristics equivalent to those in Example 1 can be obtained. In other words, according to the configuration of this embodiment, it is possible to reduce the number of quantum well layers constituting the saturable absorbing layer 16 while achieving effects equivalent to those of the first embodiment. This makes it possible to simplify the manufacturing process of the light-emitting device.

[0048] The specific number of quantum wells in this case will be explained below. In the saturable absorbing layer of Example 1, which has the same configuration as the saturable absorbing layer of the comparative example, the absorption coefficient at the laser oscillation wavelength of 940 nm at room temperature is −2141 cm as shown in FIG. -1 In other words, it is possible to generate a short optical pulse with a high peak value at this absorption coefficient. On the other hand, the absorption coefficient in the preferred wavelength range described above in Example 2, specifically in the wavelength range from 14 nm to 48 nm shorter than the wavelength corresponding to the band gap of the saturable absorbing layer, is -4012 cm -1 From -6684cm -1In both Example 1 and Example 2, the number of quantum wells in the saturable absorbing layer 16 is three, but in Example 2, the absorption coefficient is large, so by reducing the number of quantum wells, it is possible to reduce the absorption coefficient when light passes through the saturable absorbing layer 16 to the same level as in Example 1. Specifically, based on the ratio of the absorption coefficient in Example 1 to the absorption coefficient in Example 2, it is possible to reduce the number of quantum wells in the saturable absorbing layer 16 in the range of 0.32 to 0.53 times. In Example 2, the number of quantum wells is three, so the number of quantum wells can be reduced to 1 by multiplying it by 0.32.

[0049] Incidentally, the number of quantum wells in the active layer 24 in Example 2 is also 3. That is, in terms of the absorption coefficient in Example 2, a preferable ratio of the number of quantum wells between the saturable absorbing layer 16 and the active layer 24 also includes 1:3.

[0050] In addition, from the viewpoint of the temperature dependence of the absorption coefficient, the change in the absorption coefficient of the saturable absorbing layer due to temperature was 1527 cm in Example 2. -1 ], and the increase in gain of the active layer was 562 [cm -1 Therefore, from the viewpoint of reducing the amount of change in the absorption coefficient to the same extent as the amount of increase in gain, the ratio of the number of quantum wells in the saturable absorbing layer 16 to the active layer 24 of 1:3 is within a more preferable range.

[0051] From the above, an example of a more preferable range for the ratio of the number of quantum wells in the saturable absorbing layer 16 to the active layer 24 is 1:1 to 1:3. However, even if the ratio is outside this range, as described in this embodiment, the effect of this embodiment can be achieved by setting the wavelength corresponding to the band gap of the quantum wells constituting the saturable absorbing layer 16 to be longer than the laser oscillation wavelength.

[0052] In this embodiment, the active layer 24 has one pin junction, but a multi-junction configuration in which active layers 24 with pin junctions are stacked with tunnel junctions sandwiched between them can also be used for the active layer portion. In this case, the number of quantum wells in the active layer 24 is the sum of the numbers of quantum wells present in all the pin junctions in the active layer. This is because the number of quantum well layers between the upper and lower reflectors is the number of quantum wells that provide gain to light. Therefore, it is more preferable that the relationship between this sum and the number of quantum wells in the saturable absorbing layer be within the above-mentioned range.

[0053] As described above, according to this embodiment, in a VCSEL device having a saturable absorbing layer, the gain peak wavelength of the active layer is set to be shorter than the lasing wavelength of the resonator, thereby reducing the temperature dependence of the optical output characteristics. Furthermore, the wavelength corresponding to the bandgap of the quantum well constituting the saturable absorbing layer is set to be longer than the lasing wavelength, thereby further reducing the temperature dependence of the optical output characteristics.

[0054] In this embodiment, the absorption coefficient of the saturable absorbing layer 16 is increased, increasing the proportion of light absorbed within the cavity. Therefore, this design is undesirable from the perspective of light extraction efficiency at both room temperature and high temperatures, potentially leading to a decrease in optical output. On the other hand, as mentioned above, in LiDAR applications, the stability of the timing of short pulse generation is directly linked to ranging accuracy and is therefore even more important. In this embodiment, in a VCSEL device having a saturable absorbing layer 16, the gain peak wavelength of the active layer 24 is set to be shorter than the laser oscillation wavelength of the cavity. The wavelength corresponding to the bandgap of the quantum well constituting the saturable absorbing layer 16 is set to be longer than the laser oscillation wavelength, thereby canceling out the respective gains and absorptions. This configuration can be said to solve the issues described in Patent Document 1 and achieve the effect of stabilizing the timing of short pulse generation.

[0055] [Third embodiment] The light emitting device according to the third embodiment will be described with reference to Fig. 11. Components similar to those of the light emitting device according to the first or second embodiment will be given the same reference numerals, and descriptions thereof will be omitted or simplified.

[0056] The light-emitting device according to this embodiment differs from the light-emitting device according to the first embodiment in that the quantum wells constituting the active layer 24 are so-called asymmetric quantum wells, which include multiple types of quantum wells with different wavelengths corresponding to the band gaps of the quantum wells. By applying an asymmetric quantum well structure to the active layer 24, the number of control parameters increases, making it possible to design a more desirable gain shape. In addition, asymmetric quantum wells have the advantage of being able to emit light at a high energy level even when the carrier density is low.

[0057] Asymmetric quantum well structures are generally used to achieve broadband emission and gain. Therefore, they are used in light sources that emit light over a wide wavelength band, with a wavelength difference of 50 nm, such as superluminescent diodes and tunable lasers equipped with mechanisms for actively adjusting the resonant wavelength of VCSELs using MEMS or other techniques. On the other hand, asymmetric quantum wells are rarely used in conventional VCSELs, which are composed of semiconductor crystals from the lower to upper reflectors and have a solid-state resonator. This is because even if gain is generated in wavelength bands outside the oscillation wavelength range, the gain and the energy used to generate it are not effectively utilized, adversely affecting the optical output and threshold. In other words, this can lead to a decrease in optical output.

[0058] On the other hand, in this disclosure, an asymmetric quantum well structure is introduced to achieve both the temperature dependence of the absorption coefficient of the saturable absorbing layer, which is not normally present in VCSELs, and the improvement of characteristics at room temperature, thereby realizing a more preferable gain spectrum. Therefore, the gain spectrum generated by the asymmetric quantum well structure of this embodiment is not a gain spectrum that is preferable for the above-mentioned broadband light source, specifically, a flat gain spectrum over a wide wavelength band, but rather a mountain-shaped gain spectrum with a peak at a certain wavelength.

[0059] 11 is a graph showing the results of calculating the gain spectrum of the active layer in the light-emitting device according to this embodiment. In the calculation, a multi-quantum well structure was assumed for the active layer 24, including three quantum well layers with a wavelength of 920 nm corresponding to the band gap and one quantum well layer with a wavelength of 940 nm corresponding to the band gap, for a total of four quantum well layers. The laser oscillation wavelength was set to 940 nm. The vertical axis represents the carrier concentration of 3.2×10 18 cm -3 The horizontal axis represents the wavelength.

[0060] In the light emitting device of this embodiment, the gain coefficient at room temperature, i.e., the average gain coefficient of the quantum well at the laser oscillation wavelength of 940 nm at room temperature, is 510 cm as shown in FIG. -1 This value is about 369 cm in the case of the light emitting device of the first embodiment. -1 This means that the light emitting device of this embodiment is more likely to oscillate at room temperature than the light emitting device of the first embodiment, and the threshold current can be reduced.

[0061] 5, 6, and 11, let us consider a case where the temperature rises from 25°C to 85°C. This temperature difference causes a difference of about 20 nm between the wavelength shift of the gain spectrum and the optical absorption spectrum and the wavelength shift of the laser oscillation wavelength, as mentioned above. The changes in the gain coefficient of the active layer 24 and the absorption coefficient of the saturable absorbing layer 16 that accompany this 20 nm wavelength shift of the gain spectrum and the optical absorption spectrum are summarized in Figure 12.

[0062] As shown in FIG. 12, the change in light output characteristics with temperature change in the light emitting device of this embodiment (Example 3) is slightly increased compared to the first embodiment, but can be reduced more than in the comparative example described above.

[0063] As described above, according to this embodiment, in a VCSEL device having a saturable absorbing layer, the gain peak wavelength of the active layer is set to be shorter than the lasing wavelength of the resonator, thereby reducing the temperature dependence of the optical output characteristics. Furthermore, by applying an asymmetric quantum well structure to the active layer, the degree of freedom in designing the optical output characteristics can be improved.

[0064] As described above, the present disclosure is based on the idea of ​​offsetting the increase in the absorption coefficient of the saturable absorbing layer 16 due to temperature rise by designing the gain of the active layer 24 to increase with temperature rise. In other words, a configuration is required in which the gain increases as the wavelength becomes shorter from the wavelength range in which the laser oscillates, typically the laser oscillation wavelength at room temperature. Such a gain spectrum can be achieved by making the number of long-wavelength quantum wells and the number of short-wavelength quantum wells that make up the asymmetric quantum well structure equal, or by making the number of short-wavelength quantum wells greater than the number of long-wavelength quantum wells. Example 3 also has such a configuration.

[0065] Furthermore, the upper limit of the preferable range of the wavelength difference corresponding to the band gap between the quantum wells with long wavelengths and those with short wavelengths is 40 nm. That is, as is clear from Figure 5 and other figures, the half-width at half maximum (the wavelength width over which the gain is half its peak value) of the gain spectrum generated by one quantum well is 20 nm. Therefore, to achieve a configuration in which two or more quantum wells are stacked together and the gain increases as the wavelength becomes shorter from the laser oscillation wavelength at room temperature, as described above, the gain must be stacked with a width shorter than the half-width at half maximum.

[0066] When actually manufacturing a quantum well structure, the wavelength corresponding to the band gap often varies by about 3 nm to 5 nm. In other words, a wavelength difference of less than this amount essentially results in the configurations of Examples 1 and 2. Therefore, in order to stably provide a wavelength difference corresponding to the band gaps of the long-wavelength quantum well and the short-wavelength quantum well and to achieve the effects of this embodiment, it is practical to set the wavelength difference to 5 nm or more. Therefore, the preferred range of the wavelength difference corresponding to the band gaps of the long-wavelength quantum well and the short-wavelength quantum well that constitute the asymmetric quantum well of this embodiment is 5 nm to 40 nm.

[0067] The asymmetric quantum well structure of this embodiment and the configuration of Example 2 in which the wavelength corresponding to the band gap of the quantum well constituting the saturable absorbing layer 16 is set to be longer than the laser oscillation wavelength can be combined, and the preferred ranges of each can also be used.

[0068] The band gap of a quantum well is related to the PL (photoluminescence) emission wavelength, which is a common inspection item during manufacturing, and can be determined from the PL emission wavelength. The quantum well gain peak and PL emission wavelength also have a theoretically known relationship, and the quantum well gain peak wavelength under specific conditions can be determined from the PL emission wavelength.

[0069] In the light-emitting devices of the first to third embodiments, the number of electrodes is two, and these electrodes have the function of injecting current into the active layer, but no electrode is provided for electrically controlling the saturable absorbing layer. For example, in the first embodiment, current is injected into the active layer 24 by electrodes 40 and 42. In a configuration in which the optical absorption characteristics of the saturable absorbing layer 16 are not controlled by electrical means such as current injection or application of a reverse bias voltage, as described above, the oscillation timing changes when the gain of the active layer 24 and the absorption coefficient of the saturable absorbing layer 16 change with temperature. Therefore, in order to suppress the temperature change in the oscillation timing, it is important to have a configuration that offsets the gain change and absorption change due to temperature change.

[0070] On the other hand, unlike the configuration of the present disclosure, a VCSEL using a saturable absorbing layer is also known, which has a pin configuration in which both the active layer and the saturable absorbing layer are sandwiched between p-type and n-type semiconductor layers. This VCSEL has electrodes that electrically contact the p-type and n-type layers that sandwich the active layer, as well as electrodes that electrically contact the p-type and n-type layers that sandwich the saturable absorbing layer. In this configuration, one electrode can serve as any two of the four electrodes. Therefore, the number of electrodes is typically three or four.

[0071] In this configuration, carriers for light emission are injected into the active layer by applying a voltage in the forward direction of the pin. Furthermore, a voltage is applied to the saturable absorbing layer in the forward or reverse direction of the pin, and the oscillation timing is controlled by the conditions and time changes of the voltage applied to the saturable absorbing layer. In this configuration, the oscillation timing is controlled by changing the characteristics of the saturable absorbing layer, such as the absorption coefficient, by applying a voltage or current to the saturable absorbing layer. It is preferable to design the absorption coefficient of the saturable absorbing layer to be sufficiently large so as not to oscillate when laser oscillation is not occurring, while designing the absorption coefficient of the saturable absorbing layer to be sufficiently small when laser oscillation is occurring. As in the present disclosure, it is not preferable to set the gain and absorption coefficient of the saturable absorbing layer to the limits of the oscillation conditions, such that the transition from the non-oscillation state to the oscillation state occurs after a certain period of time. Instead, an absorption coefficient large enough to ensure the non-oscillation state and an absorption coefficient small enough to ensure the oscillation state are achieved by electrical control. Therefore, it is possible to further change the absorption coefficient of the saturable absorbing layer due to temperature changes through electrical control, and there is little need to offset the gain of the active layer and the absorption coefficient of the saturable absorbing layer, as in the present disclosure.

[0072] The VCSEL of Patent Document 1 has a two-electrode configuration, which offers advantages such as a simplified fabrication process and a reduced number of drive power sources. However, because the saturable absorbing layer cannot be electrically controlled, the timing of short pulse generation is primarily determined by the relationship between the gain of the active layer and the absorption coefficient of the saturable absorbing layer. This creates a problem in that the timing of short pulse generation, which is important in LiDAR systems, changes with temperature. Therefore, the configuration of the present disclosure, which offsets the gain of the active layer and the absorption coefficient of the saturable absorbing layer, does not electrically change the optical absorption characteristics of the saturable absorbing layer and is particularly effective in VCSEL configurations with only two electrodes for injecting current into the active layer.

[0073] [Fourth embodiment] A light emitting device according to a fourth embodiment will be described with reference to Figures 13 and 14. Figure 13 is a perspective view showing the light emitting device according to this embodiment. Figure 14 is a top view of the light emitting device according to this embodiment.

[0074] The light emitting device 100 according to this embodiment is a so-called VCSEL array, which is configured by arranging a plurality of the light emitting devices 100 according to the first to third embodiments in a two-dimensional array. The cross section taken along line AA' in FIG. 14 roughly corresponds to the cross section of FIG. 1. Each of the light emitting portions 50 in FIG. 13 corresponds to the mesa portion in FIG. 1. The semiconductor substrate 10 in FIG. 13 corresponds to the semiconductor substrate 10 to the n-type layer 20 in FIG. 1.

[0075] 13 and 14 show only 12 light-emitting units 50 arranged in a 4 × 3 array for simplicity of the drawings, but in a typical VCSEL array, for example, 3,600 VCSELs arranged in a 60 × 60 array are provided on the same semiconductor substrate 10. The diameter of the light-emitting units 50 is, for example, 10 μm. The light-emitting units 50 are arranged so that the centers of the light-emitting units 50 are spaced apart vertically and horizontally at intervals of, for example, 50 μm in a plan view. The chip size of the light-emitting device 100 is, for example, 3.3 mm × 3.3 mm.

[0076] The electrodes 40 corresponding to each of the light-emitting sections 50 are electrically connected to an anode common electrode 40C via wiring (not shown). The electrodes 42 corresponding to each of the light-emitting sections 50 are electrically connected to a cathode common electrode 42C. The anode common electrode 40C and the cathode common electrode 42C are electrodes common to the multiple light-emitting sections 50 that make up the VCSEL array. Au wires (not shown) are electrically and physically connected to the anode common electrode 40C and the cathode common electrode 42C. A current for driving the light-emitting device 100 is injected from an external circuit via the anode common electrode 40C and the cathode common electrode 42C. The anode common electrode 40C and the cathode common electrode 42C have a rectangular shape with a width of, for example, 100 μm and a length of, for example, 1.5 mm.

[0077] In this way, according to this embodiment, a VCSEL array can be realized using the light emitting device 100 according to the first to third embodiments.

[0078] [Fifth embodiment] The light emitting device according to the fifth embodiment will be described with reference to Fig. 15. Components similar to those of the light emitting devices according to the first to fourth embodiments are given the same reference numerals, and descriptions thereof will be omitted or simplified. Fig. 15 is a cross-sectional view showing the general configuration of the light emitting device according to this embodiment.

[0079] In this embodiment, an example will be described in which the light emitting device according to the fourth embodiment is applied to a light emitting device that emits light in the SWIR (Short Wavelength Infrared Region) band.

[0080] The light emitting device 100 according to this embodiment further includes a VCSEL chip 160 in addition to the components of the light emitting device 100 according to the fourth embodiment. The VCSEL chip 160 is bonded onto the light emitting surfaces of the plurality of light emitting units 50 that constitute the VCSEL array. The VCSEL chip 160 is a light emitting element that oscillates using light emitted from the light emitting units 50 as excitation light and emits light in the SWIR band.

[0081] The VCSEL chip 160 may be configured to include an InP substrate 162, an upper reflecting mirror 164, a resonator spacer portion 166, a lower reflecting mirror 172, and an AR (Anti-Reflection) coating 174. The upper reflecting mirror 164, the resonator spacer portion 166, and the lower reflecting mirror 172 are stacked in this order on one surface of the InP substrate 162. The AR coating 174 is provided on the other surface of the InP substrate 162. The VCSEL chip 160 is bonded onto the light emitting portion 50 so that the lower reflecting mirror 172 side faces the light emitting portion 50.

[0082] The upper reflecting mirror 164 may be formed by stacking seven pairs of stacked layers, each of which is made of an SiO layer and a TiO layer, each having an optical film thickness of ¼λc. Here, λc is the center wavelength of the high reflection band of the upper reflecting mirror 164, which is 1550 nm in this embodiment. The cavity spacer 166 may be formed by a pin junction made of an n-type layer, an undoped spacer, and a p-type layer. The undoped spacer may have, for example, five quantum well layers (only one layer is shown), each of which has an InGaAs well layer 168, e.g., 8 nm thick, sandwiched between InGaAsP light absorption layers 170. The lower reflecting mirror 172 may be formed by stacking multiple pairs of stacked layers, each of which is made of an InP layer and an InGaAsP layer, each having an optical film thickness of ¼λc. By configuring the reflectivity of upper reflecting mirror 164 to be lower than that of lower reflecting mirror 172, light oscillated between upper reflecting mirror 164 and lower reflecting mirror 172 is extracted to the InP substrate 162 side and emitted to the outside via AR coating 174. AR coating 174 serves to prevent reflection at the interface with InP substrate 162.

[0083] The light-emitting section 50 emits light with a wavelength of, for example, 940 nm. The light emitted from the light-emitting section 50 enters the cavity spacer section 166 through the lower reflecting mirror 172 and is absorbed by the InGaAsP light absorption layer 170. Electrons and holes are generated by the light absorbed by the InGaAsP light absorption layer 170, and these electrons and holes enter the InGaAs well layer 168, where their density exceeds the transparent carrier density, resulting in gain. Laser oscillation occurs in the VCSEL chip 160 in this manner, enabling the light-emitting device 100 to emit laser light with a wavelength in the 1550 nm band.

[0084] In this embodiment, the VCSEL chip 160 excited by the 940 nm wavelength light is a 1550 nm wavelength band VCSEL, but this is not limited to this. For example, the VCSEL chip 160 may be a VCSEL that emits light in a wavelength band other than the 1550 nm wavelength band, such as the 1900 nm wavelength band. Furthermore, the VCSEL chip 160 may be a VCSEL array in which multiple VCSEL elements are arranged, or an LED chip may be provided instead of the VCSEL chip 160.

[0085] [Sixth embodiment] A distance measuring device according to the sixth embodiment will be described with reference to Fig. 16. Fig. 16 is a block diagram showing a schematic configuration of the distance measuring device according to this embodiment.

[0086] The distance measuring device 200 according to this embodiment is a distance measuring device (LiDAR device) in which the light emitting device 100 according to the fourth or fifth embodiment is applied to a light source section.

[0087] The distance measuring device 200 according to this embodiment can be composed of a control unit 210, a surface-emitting laser array driver 212, a surface-emitting laser array 214, an emitting-side optical system 218, a receiving-side optical system 220, an image sensor 222, and a distance data processing unit 224.

[0088] The surface-emitting laser array 214 is a light-emitting device 100 according to the fourth or fifth embodiment mounted in a package. The surface-emitting laser array driver 212 is a driver 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. As described above, the surface-emitting laser array driver 212 injects current into the active layer, but does not perform electrical control to change the characteristics of the saturable absorption layer. Therefore, the surface-emitting laser array driver 212 is electrically connected to the p-type layer and n-type layer arranged above and below the active layer. The surface-emitting laser array 214 and the surface-emitting laser array driver 212 may be a single light-emitting device.

[0089] 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. Note that 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. 16, they are not composed of only a single convex lens-shaped member, but are composed of a lens group combining multiple lenses.

[0090] 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. Image sensor 222 may be an imaging device such as a CMOS image sensor. Distance data processing unit 224 functions as a distance information acquisition unit that generates and outputs information regarding the distance to measurement object 1000 present in the distance measurement range based on a signal from image sensor 222. Note that distance data processing unit 224 only needs to be electrically connected to image sensor 222, and may be disposed in the same package as image sensor 222 or in a package separate from image sensor 222.

[0091] 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.

[0092] As described above, a light-emitting device suitable for a LiDAR system is one capable of generating optical pulses with short optical pulse widths and high peak values. Specifically, the optical pulse width of a light source suitable for a LiDAR system is, for example, in the range of approximately 50 ps to 1 ns. However, from the perspective of VCSELs and the electrical aspects of driving VCSELs, it is not easy to generate light with such short pulse widths. Because VCSELs emit light according to the amount of current injected, in order to achieve optical pulses of approximately 50 ps to 1 ns, the current pulse driving the VCSEL must be of the same order. In other words, the frequency components from the driver to the VCSEL must have excellent electrical characteristics in high-frequency bands such as 1 GHz or 10 GHz and handle currents exceeding 1 A. This approach entails higher costs than constructing an electrical transmission section from the driver to the VCSEL using only electrical circuits that handle lower frequency bands.

[0093] Therefore, in this embodiment, the light emitting device 100 described in the fourth or fifth embodiment is used as the surface emitting laser array 214, so that the VCSEL itself generates short pulses. This avoids the high cost of the driver section and electrical transmission section, while realizing optical pulses of about 50 ps to 1 ns, which are preferable for LiDAR systems.

[0094] 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.

[0095] The laser light generated by the surface-emitting laser array 214 is emitted toward the distance measurement range by the light-emitting side optical system 218. Of the laser light irradiated onto the measurement object 1000 in 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 to the image sensor 222 by the light-receiving side optical system 220.

[0096] Each pixel of the image sensor 222 generates an electric signal pulse according to the timing of incidence of the laser light. The electric signal pulse generated by the image sensor 222 is input to the distance data processing unit 224.

[0097] The distance data processing unit 224 generates information about the distance to the measurement object 1000 along the light propagation direction based on 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.

[0098] As described above, according to this embodiment, it is possible to realize a high-performance distance measuring device equipped with a light emitting device capable of generating an optical pulse with a short optical pulse width and a high peak value.

[0099] 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.

[0100] 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.

[0101] [Seventh embodiment] A distance measuring device according to the seventh embodiment will be described with reference to Figs. 17 and 18. Fig. 17 is a block diagram showing a schematic configuration of the distance measuring device according to this embodiment. Fig. 18 is a schematic cross-sectional view showing an example configuration of a surface-emitting laser array in the distance measuring device according to this embodiment. Components similar to those in the distance measuring device according to the sixth embodiment are given the same reference numerals, and their explanation will be omitted or simplified.

[0102] 17, the distance measuring device 200 according to this embodiment differs from the distance measuring device according to the sixth embodiment in that the surface emitting laser array 214 further includes a light emission timing monitor unit 216. Other points of the distance measuring device 200 according to this embodiment are the same as those of the distance measuring device according to the sixth embodiment.

[0103] As shown in FIG. 18 , the surface-emitting laser array 214 includes a light-emitting device 100, an emission timing monitor unit 216, a base 110, and a window material 120. The base 110 is part of a package that mounts the light-emitting device 100 and the emission timing monitor unit 216, and has a recess that houses the light-emitting device 100 and the emission timing monitor unit 216. The base 110 may be made of, for example, ceramic. The window material 120 is fixed to the base 110 so as to cover the recess in the base 110 on which the light-emitting device 100 and the emission timing monitor unit 216 are mounted. The light-emitting device 100 is the light-emitting device 100 according to the fourth embodiment. The emission timing monitor unit 216 is made of, for example, a semiconductor substrate having a square shape with sides of 0.3 mm, and includes, as a light-receiving element, a photodiode with a light-receiving area having a diameter of 100 μm.

[0104] The anode common electrode 40C, the cathode common electrode 42C of the light emitting device 100, and the anode and cathode of the photodiode that constitutes the light emission timing monitor unit 216 are electrically connected to electrodes (not shown) provided on the outer periphery of the base 110. A pulse current supplied from the surface emitting laser array driver 212 is supplied to the light emitting device 100 via the electrodes provided on the base 110. In addition, an electrical signal generated by the light emission timing monitor unit 216 is supplied to the distance data processing unit 224 via the electrodes provided on the base 110.

[0105] Next, the operation of the distance measuring device according to this embodiment will be described with reference to FIGS. 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 light-emitting devices 100 of the surface-emitting laser array 214. This causes the light-emitting devices 100 to oscillate and output laser light. At this time, the pulse width of the light emitted from the light-emitting device 100 is narrower than the pulse width of the injected current, as described above.

[0106] The laser light generated by the light-emitting device 100 is emitted from the surface-emitting laser array 214 through the window material 120, and is then emitted toward the distance measurement target range by the light-emitting side optical system 218. At this time, although the window material 120 is AR coated, a portion of the light is reflected by the window material 120 and enters the light emission timing monitor unit 216.

[0107] The light emission timing monitor 216 converts the incident light into an electrical signal and outputs it to the distance data processor 224. The distance data processor 224 generates information about the distance to the measurement object 1000 along the light propagation direction based on the time difference between the timing of receiving the electrical signal pulse from the image sensor 222 and the timing of receiving the electrical signal from the light emission timing monitor 216. Then, by calculating 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 is obtained.

[0108] 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 device 100. 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.

[0109] In this regard, 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.

[0110] As described above, according to this embodiment, in a distance measuring device using an optical pulse with a high peak value and a short pulse, it is possible to further reduce the influence of changes in the environmental temperature on distance measurement accuracy.

[0111] [Eighth embodiment] The device and moving object according to the eighth embodiment will be described with reference to Fig. 19A and Fig. 19B. Fig. 19A is a block diagram showing an example of the configuration of the device according to this embodiment. Fig. 19B is a block diagram showing an example of the configuration of the moving object according to this embodiment.

[0112] 19A shows an example of the configuration of a device mounted on a vehicle as an in-vehicle camera. The device 300 has a distance measurement unit 303 that measures the distance to an object to be measured, and a collision determination unit 304 that determines whether or not there is a possibility of a collision based on the distance measured by the distance measurement unit 303. The distance measurement unit 303 may be configured, for example, by the distance measuring device 200 described in the sixth or seventh embodiment. Here, the distance measurement unit 303 is an example of a distance information acquisition means that acquires distance information to the object to be measured. In other words, the distance information is information related to the distance to the object to be measured, etc.

[0113] The device 300 is connected to a vehicle information acquisition device 310 and can acquire vehicle information such as vehicle speed, yaw rate, and steering angle. The device 300 is also connected to a control ECU 320, which is a control device that outputs a control signal to generate a braking force for the vehicle based on the determination result of the collision determination unit 304. The device 300 is also connected to an alarm device 330 that issues an alarm to the driver based on the determination result of the collision determination unit 304. For example, if the collision determination unit 304 determines that a collision is highly likely, the control ECU 320 performs vehicle control to avoid the collision and mitigate damage by applying the brakes, releasing the accelerator, suppressing engine output, etc. The alarm device 330 warns the user by sounding an alarm, displaying alarm information on the screen of a car navigation system, etc., or vibrating the seat belt or steering wheel. These devices of the device 300 function as a mobile object control unit that controls the operation of controlling the vehicle as described above.

[0114] In this embodiment, the device 300 measures the distance around the vehicle, for example, the front or rear. Fig. 19B shows the device when measuring the distance in front of the vehicle (distance measurement range 350). The vehicle information acquisition device 310, which serves as a distance measurement control means, sends an instruction to the device 300 or the distance measurement unit 303 to perform a distance measurement operation. This configuration can further improve the accuracy of distance measurement.

[0115] In this embodiment, an example of control to prevent collision with other vehicles has been described, but the present invention can also be applied to control of automatic driving by following other vehicles, control of automatic driving to prevent deviation from a lane, etc. Furthermore, the device is not limited to vehicles such as automobiles, but can be applied to moving bodies (moving devices) such as ships, aircraft, artificial satellites, industrial robots, and consumer robots. In addition, the present invention can be applied to a wide range of devices that use object recognition or biometric recognition, such as intelligent transport systems (ITS) and surveillance systems, without being limited to moving bodies.

[0116] [Modified embodiment] The present disclosure 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 embodiment 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 disclosure.

[0117] Furthermore, in the first to third 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 an InP substrate is used as the semiconductor substrate 10 include InP, InGaAs, InGaP, and InGaAsP.

[0118] Furthermore, the DBR layer in the light-emitting devices according to the first to third 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 to third embodiments, the same effects as those of the present embodiment can be achieved.

[0119] It should be noted that the above-described embodiments are merely examples of specific embodiments for carrying out the present disclosure, and the technical scope of the present disclosure should not be construed as being limited by these embodiments. In other words, the present disclosure can be carried out in various forms without departing from its technical concept or main features.

[0120] The disclosure of the above embodiment includes the following configurations. (Configuration 1) a resonator disposed on a semiconductor substrate and including a first reflector and a second reflector; a cavity spacer portion disposed between the first reflecting mirror and the second reflecting mirror and including an active layer and a saturable absorbing layer; the first reflecting mirror, the resonator spacer portion, and the second reflecting mirror are stacked in this order on the semiconductor substrate, the active layer has an asymmetric quantum well structure including a plurality of types of quantum wells having different wavelengths corresponding to bandgaps, The gain peak wavelength of the active layer is shorter than the laser oscillation wavelength of the resonator. A light emitting device characterized by: (Configuration 2) a resonator disposed on a semiconductor substrate and including a first reflector and a second reflector; a cavity spacer portion disposed between the first reflecting mirror and the second reflecting mirror and including an active layer and a saturable absorbing layer; the first reflecting mirror, the resonator spacer portion, and the second reflecting mirror are stacked in this order on the semiconductor substrate, the active layer has an asymmetric quantum well structure including a plurality of types of quantum wells having different wavelengths corresponding to bandgaps, The gain peak wavelength of the active layer is set so that the gain of the active layer at the laser oscillation wavelength of the resonator becomes a first value at a first temperature and becomes a second value greater than the first value at a second temperature higher than the first temperature. A light emitting device characterized by: (Configuration 3) The first temperature is room temperature, and the second temperature is an ambient temperature during operation. 3. The light-emitting device according to configuration 2. (Configuration 4) The gain peak wavelength is shorter than the laser oscillation wavelength. 4. The light-emitting device according to configuration 2 or 3. (Configuration 5) The active layer includes a quantum well whose band gap wavelength is shorter than the laser oscillation wavelength. 5. The light emitting device according to any one of configurations 1 to 4. (Configuration 6) The saturable absorbing layer includes a quantum well whose band gap wavelength is the same as the laser oscillation wavelength. 6. The light emitting device according to any one of configurations 1 to 5. (Configuration 7) The saturable absorbing layer includes a quantum well whose band gap wavelength is longer than the laser oscillation wavelength. 6. The light emitting device according to any one of configurations 1 to 5. (Configuration 8) The ratio of the number of quantum wells included in the saturable absorbing layer to the number of quantum wells included in the active layer is in the range of 1:1 to 1:3. 8. The light emitting device according to claim 6 or 7. (Configuration 9) The asymmetric quantum well structure includes a first quantum well having a first wavelength corresponding to the band gap and a second quantum well having a second wavelength corresponding to the band gap, and the difference between the first wavelength and the second wavelength is 5 nm or more. 9. The light emitting device according to any one of configurations 1 to 8. (Configuration 10) a resonator disposed on a semiconductor substrate and including a first reflector and a second reflector; a cavity spacer portion disposed between the first reflecting mirror and the second reflecting mirror and including an active layer and a saturable absorbing layer; the first reflecting mirror, the resonator spacer portion, and the second reflecting mirror are stacked in this order on the semiconductor substrate, a gain peak wavelength of the active layer is shorter than a laser oscillation wavelength of the resonator; The saturable absorbing layer includes a quantum well whose band gap wavelength is longer than the laser oscillation wavelength. A light emitting device characterized by: (Configuration 11) a resonator disposed on a semiconductor substrate and including a first reflector and a second reflector; a cavity spacer portion disposed between the first reflecting mirror and the second reflecting mirror and including an active layer and a saturable absorbing layer; the first reflecting mirror, the resonator spacer portion, and the second reflecting mirror are stacked in this order on the semiconductor substrate, a gain peak wavelength of the active layer is set so that a gain of the active layer at a laser oscillation wavelength of the resonator has a first value at a first temperature and a second value greater than the first value at a second temperature higher than the first temperature; The saturable absorbing layer includes a quantum well whose band gap wavelength is longer than the laser oscillation wavelength. A light emitting device characterized by: (Configuration 12) The first temperature is room temperature, and the second temperature is an ambient temperature during operation. 12. The light-emitting device according to claim 11. (Configuration 13) The gain peak wavelength is shorter than the laser oscillation wavelength. 13. The light-emitting device according to configuration 11 or 12. (Configuration 14) The active layer includes a quantum well whose band gap wavelength is shorter than the laser oscillation wavelength. 14. The light emitting device according to any one of configurations 10 to 13. (Configuration 15) The active layer has an asymmetric quantum well structure including multiple types of quantum wells with different wavelengths corresponding to the band gap. 15. The light emitting device according to any one of configurations 10 to 14. (Configuration 16) The asymmetric quantum well structure includes a first quantum well having a first wavelength corresponding to the band gap and a second quantum well having a second wavelength corresponding to the band gap, and the difference between the first wavelength and the second wavelength is 5 nm or more. 16. The light-emitting device according to configuration 15. (Configuration 17) The ratio of the number of quantum wells included in the saturable absorbing layer to the number of quantum wells included in the active layer is in the range of 1:1 to 1:3. 17. The light emitting device according to any one of configurations 10 to 16. (Configuration 18) a plurality of light-emitting sections each including the resonator, the resonator spacer section, and the saturable absorbing layer; 18. The light emitting device according to any one of configurations 1 to 17. (Configuration 19) a second cavity including a third reflecting mirror and a fourth reflecting mirror, and a second cavity spacer portion including a second active layer disposed between the third reflecting mirror and the fourth reflecting mirror, The second resonator oscillates light having a wavelength different from the laser oscillation wavelength excited in the second active layer by light having the laser oscillation wavelength. 19. The light emitting device according to any one of configurations 1 to 18. (Configuration 20) The first reflecting mirror and the second reflecting mirror are distributed Bragg reflectors. 20. The light emitting device according to any one of configurations 1 to 19. (Configuration 21) a light-emitting device according to any one of configurations 1 to 20; a light receiving device that receives light emitted from the light emitting device and reflected by the object to be measured; a distance information acquisition unit that acquires information about the distance to the object to be measured based on the time difference between the timing at which light is emitted from the light emitting device and the timing at which light is received by the light receiving device; A distance measuring device comprising: (Configuration 22) a light receiving element mounted in the same package as the light emitting device and receiving light emitted from the light emitting device; The light receiving element detects the timing at which light is emitted from the light emitting device. 22. The distance measuring device according to configuration 21. (Configuration 23) A mobile object, A distance measuring device according to configuration 21 or 22; 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: [Explanation of symbols]

[0121] 10...Semiconductor substrate 12…Lower DBR layer 16...Saturable absorbing layer 24…Active layer 28...Top DBR layer

Claims

1. a resonator disposed on a semiconductor substrate and including a first reflector and a second reflector; a cavity spacer portion disposed between the first reflecting mirror and the second reflecting mirror and including an active layer and a saturable absorbing layer; the first reflecting mirror, the resonator spacer portion, and the second reflecting mirror are stacked in this order on the semiconductor substrate, the active layer has an asymmetric quantum well structure including a plurality of types of quantum wells having different wavelengths corresponding to bandgaps, The gain peak wavelength of the active layer is shorter than the laser oscillation wavelength of the resonator. A light emitting device characterized by:

2. a resonator disposed on a semiconductor substrate and including a first reflector and a second reflector; a cavity spacer portion disposed between the first reflecting mirror and the second reflecting mirror and including an active layer and a saturable absorbing layer; the first reflecting mirror, the resonator spacer portion, and the second reflecting mirror are stacked in this order on the semiconductor substrate, the active layer has an asymmetric quantum well structure including a plurality of types of quantum wells having different wavelengths corresponding to bandgaps, The gain peak wavelength of the active layer is set so that the gain of the active layer at the laser oscillation wavelength of the resonator becomes a first value at a first temperature and becomes a second value greater than the first value at a second temperature higher than the first temperature. A light emitting device characterized by:

3. The first temperature is room temperature, and the second temperature is an ambient temperature during operation.

3. The light emitting device according to claim 2.

4. The gain peak wavelength is shorter than the laser oscillation wavelength.

3. The light emitting device according to claim 2.

5. The active layer includes a quantum well whose band gap wavelength is shorter than the laser oscillation wavelength.

5. The light emitting device according to claim 1, wherein the light emitting device is a light emitting device.

6. The saturable absorbing layer includes a quantum well whose band gap wavelength is the same as the laser oscillation wavelength.

5. The light emitting device according to claim 1, wherein the light emitting device is a light emitting device.

7. The saturable absorbing layer includes a quantum well whose band gap wavelength is longer than the laser oscillation wavelength.

5. The light emitting device according to claim 1, wherein the light emitting device is a light emitting device.

8. The ratio of the number of quantum wells included in the saturable absorbing layer to the number of quantum wells included in the active layer is in the range of 1:1 to 1:

3.

7. The light emitting device according to claim 6.

9. The asymmetric quantum well structure includes a first quantum well having a first wavelength corresponding to the band gap and a second quantum well having a second wavelength corresponding to the band gap, and the difference between the first wavelength and the second wavelength is 5 nm or more.

5. The light emitting device according to claim 1, wherein the light emitting device is a light emitting device.

10. a resonator disposed on a semiconductor substrate and including a first reflector and a second reflector; a cavity spacer portion disposed between the first reflecting mirror and the second reflecting mirror and including an active layer and a saturable absorbing layer; the first reflecting mirror, the resonator spacer portion, and the second reflecting mirror are stacked in this order on the semiconductor substrate, a gain peak wavelength of the active layer is shorter than a laser oscillation wavelength of the resonator; The saturable absorbing layer includes a quantum well whose band gap wavelength is longer than the laser oscillation wavelength. A light emitting device characterized by:

11. a resonator disposed on a semiconductor substrate and including a first reflector and a second reflector; a cavity spacer portion disposed between the first reflecting mirror and the second reflecting mirror and including an active layer and a saturable absorbing layer; the first reflecting mirror, the resonator spacer portion, and the second reflecting mirror are stacked in this order on the semiconductor substrate, a gain peak wavelength of the active layer is set so that a gain of the active layer at a laser oscillation wavelength of the resonator has a first value at a first temperature and a second value greater than the first value at a second temperature higher than the first temperature; The saturable absorbing layer includes a quantum well whose band gap wavelength is longer than the laser oscillation wavelength. A light emitting device characterized by:

12. The first temperature is room temperature, and the second temperature is an ambient temperature during operation.

12. The light emitting device according to claim 11.

13. The gain peak wavelength is shorter than the laser oscillation wavelength.

12. The light emitting device according to claim 11.

14. The active layer includes a quantum well whose band gap wavelength is shorter than the laser oscillation wavelength.

14. The light emitting device according to claim 10, wherein the light emitting device is a light emitting device.

15. The active layer has an asymmetric quantum well structure including multiple types of quantum wells with different wavelengths corresponding to the band gap.

14. The light emitting device according to claim 10, wherein the light emitting device is a light emitting device.

16. The asymmetric quantum well structure includes a first quantum well having a first wavelength corresponding to the band gap and a second quantum well having a second wavelength corresponding to the band gap, and the difference between the first wavelength and the second wavelength is 5 nm or more.

16. The light emitting device according to claim 15.

17. The ratio of the number of quantum wells included in the saturable absorbing layer to the number of quantum wells included in the active layer is in the range of 1:1 to 1:

3.

14. The light emitting device according to claim 10, wherein the light emitting device is a light emitting device.

18. a plurality of light-emitting sections each including the resonator, the resonator spacer section, and the saturable absorbing layer; 14. The light emitting device according to claim 1, wherein the light emitting device is a light emitting device.

19. a second cavity including a third reflecting mirror and a fourth reflecting mirror, and a second cavity spacer portion including a second active layer disposed between the third reflecting mirror and the fourth reflecting mirror, The second resonator oscillates light having a wavelength different from the laser oscillation wavelength excited in the second active layer by light having the laser oscillation wavelength.

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

20. The first reflecting mirror and the second reflecting mirror are distributed Bragg reflectors.

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

21. A light emitting device according to any one of claims 1 to 4 and 10 to 13; a light receiving device that receives light emitted from the light emitting device and reflected by the object to be measured; a distance information acquisition unit that acquires information about the distance to the object to be measured based on the time difference between the timing at which light is emitted from the light emitting device and the timing at which light is received by the light receiving device; A distance measuring device comprising:

22. a light receiving element mounted in the same package as the light emitting device and receiving light emitted from the light emitting device; The light receiving element detects the timing at which light is emitted from the light emitting device.

22. The distance measuring device according to claim 21.

23. A mobile object, a distance measuring device according to claim 21; 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:

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