Semiconductor laser

Abstract

This semiconductor laser (10) comprises, in the following order, a waveguide structure equipped with a first semiconductor layer (112), an active layer (113), and a second semiconductor layer (114), a p-type semiconductor layer (115_1) arranged in contact with the active layer on one side surface thereof, an n-type semiconductor layer (115_2) arranged in contact with the active layer on the other side surface thereof, a reflector (12) optically coupled with one end of the active layer in the waveguide direction, a waveguide layer (132) optically coupled with the other end of the active layer in the waveguide direction, diffraction grating (131) arranged on one of the lower surface and the upper surface of the waveguide layer, and a refractive index control unit (16) that changes the refractive index of the waveguide layer.　As a result, the semiconductor laser of the present invention makes it possible to provide suitable operation at high temperatures by means of a simple configuration.

Description

[Technical field]

[0001] The present invention relates to a semiconductor laser having a diffraction grating and capable of operating at high temperatures. [Background technology]

[0002] In recent years, in order to cope with the rapid increase in transmission capacity on the Internet, power saving in optical devices is required, and in particular, semiconductor lasers that can operate over a wide temperature range from room temperature to high temperatures are required.

[0003] Furthermore, as the density of module packaging of optoelectronic devices increases, the device temperature increases, and therefore semiconductor lasers capable of operating at high temperatures are required.

[0004] Conventionally, semiconductor lasers, such as distributed feedback laser diodes (DFB lasers), can oscillate in a single mode due to their configuration consisting of an active layer with a quantum well structure and a resonator structure such as a diffraction grating (Non-Patent Documents 1 and 2). Here, in order to obtain good laser characteristics, it is necessary that the gain wavelength and the resonant wavelength of the active layer match. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] T. Fujii et al., “Heterogeneously Integrated Membrane Lasers on Si Substrate for Low Operating Energy Optical Links,” in IEEE Journal of Selected Topics in Quantum Electronics, vol. 24, no. 1, pp. 1-8, Jan.-Feb. 2018, Art no. 1500408, doi: 10.1109 / JSTQE.2017.2778510. [Non-Patent Document 2] “Widely tunable laser with lattice filter on Si photonic platform,” Takuma Aihara, Tatsurou Hiraki, Takuro Fujii, Koji Takeda, Tai Tsuchizawa, Takaaki Kakitsuka, Hiroshi Fukuda, Shinji Matsuo, Compound Semiconductor Week 2021 (CSW 2021) TuA2-5

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[0006] In conventional DFB lasers, the temperature dependence of the gain wavelength and the temperature dependence of the refractive index are different, so that changing the operating temperature causes a mismatch between the material gain and the oscillation wavelength, resulting in degradation of the characteristics.

[0007] Therefore, in conventional DFB lasers, in order to operate with good characteristics at high temperatures, configurations have been disclosed that include a temperature controller to operate at low temperatures, or that integrate a semiconductor modulator and a semiconductor optical amplifier, or that use a material that is excellent for high-temperature operation in the active layer (Non-Patent Documents 3 to 6).

[0008] However, these structures are complicated, which causes problems such as a complicated manufacturing process and increased manufacturing costs. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, the semiconductor laser according to the present invention comprises: A semiconductor laser, The waveguide structure includes, in order, a first semiconductor layer, an active layer, and a second semiconductor layer; a p-type semiconductor layer arranged in contact with one side surface of the active layer; an n-type semiconductor layer arranged in contact with the other side surface of the active layer; a reflector optically coupled to one end of the active layer in the waveguiding direction; a waveguide layer optically coupled to the other end of the active layer in the waveguiding direction; a diffraction grating arranged on one of the lower surface and the upper surface of the waveguide layer; and a refractive index control section that changes the refractive index of the waveguide layer. The refractive index of the waveguide layer is changed by the refractive index control section, the Bragg wavelength of the waveguide layer is shifted to the long wavelength side, and the Bragg wavelength of the waveguide layer and the resonant wavelength on the long wavelength side of the reflector coincide with the gain peak of the active layer, which shifts to the long wavelength side when the temperature of the semiconductor laser increases, and oscillation occurs. do. Furthermore, a method for controlling a semiconductor laser according to the present invention is a method for controlling a semiconductor laser including an active layer, a reflector optically coupled to one end of the active layer in a waveguiding direction, a waveguide layer optically coupled to the other end of the active layer in the waveguiding direction and having a diffraction grating, and a refractive index control section for changing the refractive index of the waveguide layer, wherein the refractive index of the waveguide layer is changed by the refractive index control section to shift the Bragg wavelength of the waveguide layer to the long wavelength side, and the Bragg wavelength of the waveguide layer and the resonant wavelength on the long wavelength side of the reflector are made to coincide with a gain peak of the active layer, which shifts to the long wavelength side when the temperature of the semiconductor laser increases, thereby causing oscillation. Effect of the Invention

[0010] According to the present invention, it is possible to provide a semiconductor laser that can achieve good high temperature operation with a simple configuration. [Brief description of the drawings]

[0011] [Figure 1A] FIG. 1A is a top perspective view showing the configuration of a semiconductor laser according to a first embodiment of the present invention. [Figure 1B] FIG. 1B is a cross-sectional view taken along line IB-IB' showing the configuration of a semiconductor laser according to the first embodiment of the present invention. [Figure 1C] FIG. 1C is a cross-sectional view taken along line IC-IC' showing the configuration of a semiconductor laser according to the first embodiment of the present invention. [Figure 2A] FIG. 2A is a diagram for explaining the operation of the semiconductor laser according to the first embodiment of the present invention. [Figure 2B] FIG. 2B is a diagram for explaining the operation of the semiconductor laser according to the first embodiment of the present invention. [Figure 2C]FIG. 2C is a diagram for explaining the operation of the semiconductor laser according to the first embodiment of the present invention. [Diagram 3] FIG. 3 is a diagram for explaining the operation of the semiconductor laser according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a top perspective view showing the configuration of a semiconductor laser according to the second embodiment of the present invention. [Diagram 5] FIG. 5 is a top perspective view showing an example of the configuration of a semiconductor laser according to the second embodiment of the present invention. [Figure 6] FIG. 6 is a top perspective view showing an example of the configuration of a semiconductor laser according to the second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] <First embodiment> A first embodiment of the present invention will be described with reference to FIGS. 1A to 3. FIG.

[0013] <Configuration of semiconductor laser> The semiconductor laser according to this embodiment includes a gain region 11, a ring resonator 12, and a DBR (Distributed Bragg Reflector) region 13 on an SiO 2 101, as shown in FIG. 1A.

[0014] Here, the SiO2 101 may be made of a dielectric material other than SiO2, such as SiN or SiNO. The SiO2 101 is formed on a substrate. The substrate is made of Si, and may be made of a semiconductor or dielectric material other than Si.

[0015] As shown in Fig. 1B, the gain region 11 is formed into a waveguide structure by stacking a first semiconductor layer (InP) 112, a multi quantum well (MQW) 113 as an active layer, and a second semiconductor layer (InP) 114 on SiO2 101. A p-type InP layer 115_1 is disposed in contact with one side of the width direction (X direction in the figure) of this waveguide structure, and a p-type electrode (e.g., gold) 117_1 is provided thereon via a p-type contact layer (e.g., p-type InGaAs) 116_1. An n-type InP layer 115_2 is disposed in contact with the other side, and an n-type electrode (e.g., gold) 117_2 is provided thereon via an n-type contact layer (e.g., n-type InGaAs) 116_2.

[0016] Here, for example, the MQW active layer 113 is composed of an InGaAsP well layer and an InGaAsP barrier layer in the 1.55 μm wavelength band, and has a thickness of about 105 nm for six periods. The first semiconductor layer (InP) 112 and the second semiconductor layer (InP) 114 have thicknesses of 165 nm and 80 nm, respectively. The SiO2 101 has a thickness of 2 μm, and the p-type InP layer 115_1 and the n-type InP layer 115_2 have a thickness of 350 nm.

[0017] Here, the MQW active layer 113 may be in the 1.31 μm wavelength band. The MQW may be made of InGaAs, InGaAlAs, GaInNAs, etc., other than InGaAsP. The period, thickness, and other configurations of the MQW may be other configurations.

[0018] As shown in FIG. 1A, the ring resonator 12 is optically coupled to the gain region 11 in the waveguiding direction via a taper optical coupler 14 .

[0019] In the ring resonator 12, two waveguides 122_1 and 122_2 are optically coupled to a ring waveguide 121, and the two waveguides 122_1 and 122_2 are multiplexed or split by a taper optical coupler .

[0020] Here, the ring waveguide 121 and the taper optical coupler 14 are made of InP.

[0021] 1A, DBR region 13 is connected to gain region 11 on the opposite side to ring resonator 12 in the waveguiding direction (Y direction in the figure). DBR region 13 may be optically coupled to gain region 11.

[0022] As shown in FIG. 1C, the DBR region 13 includes an InP waveguide layer 132 on an SiO2 layer 101, an SiO2 clad 133 covering the InP waveguide layer 132, and a heater 16 on the upper surface of the SiO2 clad 133.

[0023] In the DBR region 13, a DBR diffraction grating 131 is provided at the boundary between the upper surface of the InP waveguide layer 132 and the SiO2 cladding 133. Alternatively, the DBR diffraction grating 131 may be provided at the boundary between the lower surface of the InP waveguide layer 132 and the SiO2 cladding 133.

[0024] Here, in the DBR diffraction grating 131, for example, the pitch (period) is about 200 nm to 300 nm, the depth is about 10 nm to 50 nm, and is set according to a desired emission (oscillation) wavelength and coupling coefficient. It is desirable to set the coupling coefficient so that the stop band width of the DBR is approximately the same as the FSR interval of the ring resonator described later.

[0025] In the DBR region 13, the heater 16 changes the temperature of the InP waveguide layer 132 to change the refractive index, which changes the coupling coefficient of the diffraction grating 131 of the InP waveguide layer 132, thereby changing the peak wavelength.

[0026] The heater 16 may be made of metal or resin. Although the heater 16 is disposed on the upper surface of the SiO2 clad 133 in the above example, the heater 16 may be embedded in the SiO2 clad 133 or the SiO2 101. Any configuration may be used as long as it can change the temperature of the InP waveguide layer 132.

[0027] Here, for example, the lengths of the gain region 11 and the DBR region 13 are 75 μm and 10 μm, respectively, and the width of the active layer 113 in the gain region 11 and the width of the InP waveguide 122 in the DBR region 13 are about 1.0 μm. Here, since the DBR region 13 is disposed on the light emission side, if it is too long, the reflectance will increase and the light will not be efficiently emitted (extracted). Therefore, it is desirable to set the reflectance of the DBR region 13 to be 5 to 50%.

[0028] The width of the ring waveguide 121 and the width of the waveguide coupled to the ring waveguide 121 are about 0.4 μm. The diameter of the ring waveguide 121 is about 5.0 to 10.0 μm.

[0029] The output waveguide 15 has a tapered shape that narrows toward the output end. The width of the tip (output end) is about 0.1 μm. This allows optical coupling to a waveguide disposed above or below the waveguide 15, for example, and emits laser light.

[0030] Moreover, the output waveguide 15 may simply be a straight waveguide, and the laser light may be emitted through this waveguide.

[0031] <Operation of semiconductor laser> The operation of the semiconductor laser 10 according to the present embodiment will be described below.

[0032] In the semiconductor laser 10, light is emitted in the gain region 11 by current injection, and the light is output to the ring resonator 12 side. The light is split by the tapered optical coupler 14, and in the ring resonator 12, the light propagates through two waveguides 122_1 and 122_2, respectively, and is coupled to the ring waveguide 121.

[0033] Of the two waveguides 122_1 and 122_2, the light propagating through one waveguide 122_1 and coupled to the ring waveguide 121 circulates clockwise around the ring waveguide 121, then couples with the other waveguide 122_2 and returns to the tapered optical coupler 14. Meanwhile, the light propagating through the other waveguide 122_2 and coupled to the ring waveguide 121 circulates counterclockwise around the ring waveguide 121, then couples with one waveguide 122_1 and returns to the optical coupler 14.

[0034] The light returning from the ring waveguide 12 is multiplexed by the tapered optical coupler 14. In the ring resonator, only the light with a wavelength that matches the resonant wavelength of the ring returns to the gain region. There is not just one resonant wavelength, but multiple resonant wavelengths according to the number of revolutions of the ring.

[0035] On the other hand, the light emitted from the gain region 11 toward the DBR region 13 selectively returns to the gain region in a mode that matches the reflection spectrum of the DBR diffraction grating 131. The reflection spectrum has a shape centered on the Bragg wavelength of the diffraction grating and has a finite stop band width determined by the diffraction grating coupling coefficient and the diffraction grating length. Therefore, oscillation occurs at the wavelength selected by the DBR diffraction grating 131 among the resonant wavelengths of the ring resonator 12, and is emitted as laser light (arrow 17 in FIG. 1A).

[0036] 2A and 2B show the resonant wavelength S11 of ring resonator 12 (indicated by solid and dotted arrows in the figures), the reflection spectrum S12 of DBR diffraction grating 131, and the gain spectrum S113 of the MQW active layer in a semiconductor laser in which ring resonator 12 and DBR diffraction grating 131 are integrated in the gain region.

[0037] FIG. 2A shows wavelength vs. spectrum (1_1) at room temperature when the temperature is not controlled by a heater, and wavelength vs. spectrum (1_2) at a high temperature.

[0038] In this case, the DBR diffraction grating 131 selects one wavelength (for example, λ1_1) from among the resonant wavelengths of the ring resonator 12 and oscillates (1_1 in the drawing).

[0039] At high temperatures, the gain peak S113 of the MQW active layer shifts to the longer wavelength side (wavelength λ1_a) and the intensity decreases. Meanwhile, the oscillation wavelength by the ring resonator 12 and the DBR diffraction grating 131 also shifts to the longer wavelength side, but the shift in this wavelength (λ1_1') is smaller than the shift in the gain peak. As a result, a misalignment occurs between the gain peak (λ1_a) of the MQW active layer and the peak of the oscillation wavelength (λ1_1') (1_2 in the figure). This causes the characteristics of this laser to deteriorate at high temperatures.

[0040] FIG. 2B shows wavelengths vs. spectra (1_3) at room temperature and (1_4) at high temperature when the temperature is controlled by a heater using the semiconductor laser 10 according to the present embodiment.

[0041] In the semiconductor laser 10, at room temperature, with the heater 16 off, the oscillation wavelength of the ring resonator 12 and the DBR diffraction grating 131 and the wavelength of the gain peak of the MQW active layer 113 match at wavelength λ1_1 (1_3 in the figure).

[0042] At high temperatures, the heater 16 disposed near the InP waveguide layer 132 having the DBR diffraction grating 131 is turned on to raise the temperature (for example, to about 100° C.) to increase the temperature of the InP waveguide layer 132 of the DBR diffraction grating 131. This increases the refractive index of the InP waveguide layer 132 of the DBR diffraction grating 131, and the Bragg wavelength of the DBR diffraction grating 131 shifts to the longer wavelength side.

[0043] As a result, in the semiconductor laser 10, the Bragg wavelength of the DBR diffraction grating 131 coincides with the resonance wavelength on the long wavelength side of the ring resonator 12, and the laser oscillates at an emission wavelength (λ1_2) on the long wavelength side.

[0044] At high temperatures, the gain peak of the MQW active layer 113 also shifts to the longer wavelength side as described above (1_4 in the figure).

[0045] In this manner, in the semiconductor laser 10, at high temperatures, the resonant wavelength on the long wavelength side of the ring resonator 12, which coincides with the Bragg wavelength of the DBR diffraction grating 131, coincides with the gain peak of the MQW active layer 113, and thus the laser oscillates. This suppresses a decrease in output power at high temperatures, and provides favorable high-temperature operating characteristics.

[0046] According to the semiconductor laser of the present embodiment, the decrease in output power at high temperatures is suppressed, and good high-temperature operating characteristics are obtained.

[0047] In the semiconductor laser 10, the free-spectral range (FSR) can be increased by reducing the circumferential length, i.e., the diameter, of the ring resonator 12. Furthermore, if a semiconductor such as InP or silicon is used for the ring resonator 12 and air or a dielectric such as SiO2, SiN, or SiON is used for the cladding, the refractive index difference between the core and the cladding is large, and light can be strongly confined within the optical waveguide, making it possible to reduce the bending radius and obtain a ring resonator with a large FSR. In this way, the semiconductor laser 10 uses the ring resonator 12, and can operate over a wide bandwidth.

[0048] In addition, in the DBR region 13, it is sufficient to select one of the resonant wavelengths of the ring resonator 12. If the stop band width of the DBR resonator 131 is too wide, it may oscillate in two or more modes, and if it is too narrow, it may not oscillate in any mode. By making it approximately the same as the FSR interval of the ring resonator, it becomes easy to stably select one mode. The reflectance of the DBR mirror may be determined according to the desired characteristics. The diffraction grating coupling coefficient κ=1000 cm, which results in a stop band width of approximately 20 nm, is -1 The result of calculating the reflectance of this diffraction grating is shown in Figure 2C. The desired reflectance differs depending on the desired characteristics, but it should be approximately 5% to 60%, and in this case the DBR region length is 2.5 to 10.5 μm.

[0049] <Effects of semiconductor lasers> FIG. 3 shows the calculation results of the temperature dependence of the oscillation peak wavelength and the gain peak wavelength in a semiconductor laser.

[0050] In the calculations, experimental data obtained from a semiconductor (DFB) laser was used to set the gain temperature characteristics and the oscillation wavelength temperature dependence to 0.4 nm / K and 0.085 nm / K, respectively. The transmission refractive index was set to 2.7 for the 1.55 μm wavelength band and 2.9 for the 1.31 μm wavelength band. The calculations were also performed by changing the active layer length so that K·L=5.

[0051] As shown in FIG. 3, when an oscillation wavelength 1_5 in a semiconductor laser is made to coincide with a gain peak wavelength 1_6 at room temperature and the temperature is increased, both the oscillation wavelength 1_5 and the gain peak wavelength 1_6 shift to the longer wavelength side.

[0052] Here, the shift amount of the gain peak wavelength 1_6 is larger than the shift amount of the oscillation wavelength 1_5, and the difference is 18.9 nm (indicated by an arrow in the figure) at 80° C. At this time, since the full width at half maximum of the gain spectrum of a normal MQW active layer 113 is about 40 nm, it is estimated that the gain is reduced to about half.

[0053] In this way, assuming that a semiconductor laser operates at a temperature change between room temperature and a high temperature (e.g., about 80°C), it is desirable to have a structure that allows the oscillation wavelength to be shifted by about 20 nm. In the present invention, the FSR interval can be freely set by changing the diameter of the ring, making it possible to switch wavelengths at desired wavelength intervals.

[0054] For example, in a configuration where a DFB laser is used to oscillate, to achieve a similar wavelength switching function, two oscillation wavelengths can be obtained by using a uniform diffraction grating with a widened DFB stop band width. The difference between the wavelength oscillated at room temperature and the wavelength oscillated at high temperatures is determined by the stop band width of the DFB diffraction grating. Here, the DFB stop band width depends almost entirely on the coupling coefficient of the diffraction grating.

[0055] Therefore, in order to widen the operating wavelength range of the laser, that is, the stop band width, it is necessary to increase the coupling coefficient of the diffraction grating.

[0056] However, when the coupling coefficient of the diffraction grating is increased, the product κL with the active layer length becomes large, and it becomes difficult to oscillate in a stable single mode due to the effects of spatial hole burning, etc. This problem is prominent in lasers having a long active layer, for example, exceeding 300 μm.

[0057] On the other hand, in the semiconductor laser according to the present embodiment, the resonant wavelength interval is determined by the FSR interval of the ring resonator, so the operating wavelength range of the laser can be widened regardless of the coupling coefficient of the diffraction grating. Therefore, even in a laser with a long active layer, it is possible to easily and stably oscillate in a single mode and over a wide band.

[0058] <Second embodiment> A semiconductor laser according to a second embodiment of the present invention will be described with reference to FIG.

[0059] <Configuration of semiconductor laser> As shown in FIG. 4, the semiconductor laser 20 according to this embodiment includes a gain region 11, a ring resonator 22, a DBR (Distributed Bragg Reflector) region 13, and a loop mirror 23 on an SiO 2 101.

[0060] In the ring resonator 22, two waveguides 222_1 and 222_2 are optically coupled to a ring waveguide 221, and one of the two waveguides 222_1 and 222_2, the waveguide 222_1, is optically coupled to the gain region 11 via a taper 14. The other waveguide 222_2 has a loop mirror 23 at one end. Here, the ring waveguide 221, the taper 14, and the loop mirror 23 are made of InP. The other configuration is similar to that of the first embodiment.

[0061] In the semiconductor laser 20, light is emitted in the gain region 11 by current injection, and is output to the ring resonator 22 side via the taper 14. In the ring resonator 22, the light propagates through one waveguide 222_1 and is coupled to the ring waveguide 221.

[0062] The light coupled to the ring waveguide 221 circulates clockwise through the ring waveguide 221. A part of the circulating light is coupled to the other waveguide 222_2, propagates through the other waveguide 222_2, and is reflected by the loop mirror 23. The reflected light is again coupled to the ring waveguide 221, and circulates counterclockwise through the ring waveguide 221. A part of the circulating light is coupled to one waveguide 222_1, propagates through the other waveguide 222_1, and returns to the gain region 11 via the taper 14.

[0063] On the other hand, similarly to the first embodiment, the light emitted from the gain region toward the DBR region 13 selectively returns to the gain region in a mode that matches the reflection spectrum of the DBR diffraction grating 131. Therefore, oscillation occurs at the wavelength selected by the DBR diffraction grating 131 among the resonant wavelengths of the ring resonator 22, and is emitted as a laser beam.

[0064] In this embodiment, an example in which the loop mirror 23 is used has been described, but the present invention is not limited to this. Instead of the loop mirror 23, a DBR diffraction grating 33 may be formed at the end of the other waveguide 222_2 as shown in FIG. 5, and any configuration (light reflecting portion) that reflects the oscillation light emitted from the ring resonator 22 may be used.

[0065] In the embodiment of the present invention, an example using a ring resonator 22 has been shown, but the present invention is not limited thereto. As shown in Fig. 6, a sampled grating 42 may be formed in a waveguide 41 optically coupled to the gain region 11. Like the ring resonator, the sampled grating can also generate oscillation light by reflecting light emitted from the gain region 11 in multiple modes, and thus has the same effect as the embodiment of the present invention. In this way, it is sufficient if the sampled grating is optically coupled to the gain region 11, reflects light emitted from the gain region 11 in multiple modes, and generates oscillation light, thereby functioning as a reflector.

[0066] In the embodiment of the present invention, an example in which the wavelength of the DBR region is shifted by a heater has been shown, but this is not limiting. An electrode connected to a power source may be disposed in the waveguide layer of the DBR region, a reverse bias may be applied to extract carriers, and the refractive index may be changed to shift the wavelength of the DBR region. In this way, it is sufficient to have a configuration for changing the refractive index of the DBR region (hereinafter referred to as a "refractive index control section").

[0067] Here, if the refractive index control section is a heater, the heater can be turned on to increase the temperature of the DBR region and increase the refractive index. Also, the refractive index control section can be turned on to apply a reverse bias to the DBR region and extract carriers to increase the refractive index. In this way, with the refractive index control section on, the refractive index of the DBR region can be increased and the wavelength of the DBR region can be shifted to the longer wavelength side.

[0068] In the embodiment of the present invention, the state in which the emission wavelength of the ring resonator and the Bragg wavelength of the DBR diffraction grating match refers to a state in which an emission peak in the emission spectrum of the ring resonator overlaps with a broad peak in the reflection spectrum of the DBR diffraction grating, as shown in Fig. 2A. In this case, only one emission (for example, on the short wavelength side) of the ring resonator receives feedback from the DBR diffraction grating, so that the emission on the short wavelength side can be extracted in the ring resonator.

[0069] In the embodiment of the present invention, an example has been shown in which the ring resonator and the DBR region are optically coupled to the gain region. In this case, however, it is sufficient that the waveguide in the ring resonator and the DBR region is optically coupled to the active layer of the gain region.

[0070] In the embodiment of the present invention, an example of the configuration of a semiconductor laser having a wavelength band of 1.55 μm and 1.31 μm has been shown, but other wavelength bands may be used. Also, an example of the configuration using InP-based compound semiconductors as the layer configuration of the semiconductor laser such as the active layer, the waveguide layer, the p-type and n-type semiconductor layers has been shown, but other InP-based compound semiconductors may be used, or other semiconductors such as GaAs-based and Si-based may be used, and it is sufficient to use materials that can form a semiconductor laser.

[0071] In the embodiment of the present invention, the structure, dimensions, materials, etc. of each component in the configuration and manufacturing method of the semiconductor laser are shown as examples, but the present invention is not limited to these. Anything that can exert the function and effect of the semiconductor laser can be used. [Industrial Applicability]

[0072] The present invention can be applied to light-emitting devices in Internet communication systems, computer systems, and the like. [Explanation of symbols]

[0073] 10 Semiconductor laser 112 First semiconductor layer 113 Active layer 114 Second semiconductor layer 115_1 p-type semiconductor layer 115_2 n-type semiconductor layer 12 Reflector (ring resonator) 131 Diffraction Grating 132 Waveguide Layer 16 Refractive index control section

Claims

1. A semiconductor laser, a waveguide structure comprising, in order, a first semiconductor layer, an active layer, and a second semiconductor layer; a p-type semiconductor layer disposed in contact with one side surface of the active layer; an n-type semiconductor layer disposed in contact with the other side surface of the active layer; a reflector optically coupled to one end of the active layer in a waveguiding direction; a waveguide layer optically coupled to the other end of the active layer in the waveguiding direction; a diffraction grating disposed on one of a lower surface and an upper surface of the waveguide layer; a refractive index control section that changes the refractive index of the waveguide layer; Equipped with The refractive index of the waveguide layer is changed by the refractive index control section, the Bragg wavelength of the waveguide layer is shifted to the long wavelength side, and the Bragg wavelength of the waveguide layer and the resonant wavelength on the long wavelength side of the reflector coincide with the gain peak of the active layer, which shifts to the long wavelength side when the temperature of the semiconductor laser increases, and oscillation occurs. A semiconductor laser characterized by:

2. The reflector generates oscillating light of a plurality of modes, When the refractive index control section is in an off state, the oscillating light having a predetermined wavelength is selected by the diffraction grating from among the oscillating light of the plurality of modes, and is oscillated; When the refractive index control section is in an on state, the oscillating light having a wavelength longer than a predetermined wavelength among the oscillating light of the plurality of modes is selected by the diffraction grating and oscillated.

2. The semiconductor laser according to claim 1 .

3. The reflector is a ring resonator.

3. The semiconductor laser according to claim 1, wherein the first and second electrodes are arranged in a first direction.

4. A loop mirror is optically coupled to the ring resonator.

4. The semiconductor laser according to claim 3.

5. a waveguide optically coupled to the ring resonator and having a diffraction grating at one end; 4. The semiconductor laser according to claim 3.

6. The reflector is a waveguide having a sampled grating.

3. The semiconductor laser according to claim 1, wherein the first and second electrodes are arranged in a first direction.

7. The refractive index control section is a heater.

7. The semiconductor laser according to claim 1, wherein the first and second electrodes are arranged in a first direction.

8. The refractive index control section is an electrode connected to a power source and disposed on the waveguide layer, and a bias is applied to the electrode to change the carrier density of the waveguide layer.

7. The semiconductor laser according to claim 1, wherein the first and second electrodes are arranged in a first direction.

9. A method for controlling a semiconductor laser comprising: an active layer; a reflector optically coupled to one end of the active layer in a waveguiding direction; a waveguide layer optically coupled to the other end of the active layer in the waveguiding direction and having a diffraction grating; and a refractive index control section for changing a refractive index of the waveguide layer, comprising: The refractive index of the waveguide layer is changed by the refractive index control section, the Bragg wavelength of the waveguide layer is shifted to the long wavelength side, and the Bragg wavelength of the waveguide layer and the resonant wavelength on the long wavelength side of the reflector are made to coincide with the gain peak of the active layer, which shifts to the long wavelength side when the temperature of the semiconductor laser increases, to cause oscillation.

23. A method for controlling a semiconductor laser comprising the steps of:

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