JP2013168513A - Semiconductor laser and optical semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser that allows achieving a high output.SOLUTION: A semiconductor laser 10 includes an active layer 2 formed on a substrate 1, a formation layer 3 having a diffraction grating region 31 and non-diffraction grating regions 32 and 33, and a cladding layer 4. In the formation layer 3, the diffraction grating region 31 is formed in a region apart from an emission end face 7, the non-diffraction grating region 32 is formed on the emission end face 7 side, and the ratio of the non-diffraction grating region 32 relative to the entire region 31, 32, and 33 of the formation layer 3 is set so as to reach a predetermined value.

Description

  The present invention relates to a semiconductor laser having a diffraction grating.

  With the spread of optical communication systems, the importance of semiconductor lasers used as communication light sources is increasing. Under such circumstances, for example, in a distributed feedback (DFB) laser disclosed in Non-Patent Document 1, a diffraction grating is provided on the active region, and a plurality of longitudinal modes are selected by wavelength selection of the diffraction grating. One mode is selected from the above to obtain single mode oscillation.

L.A. Coldren et al. “Diode lasers and photonic integrated circuits” Wiley, 1995, p.102-104

  The DFB laser disclosed in Non-Patent Document 1 has a configuration in which a diffraction grating is formed over the entire active region. However, the light confined inside the resonator becomes too strong, and the power of the light output tends to be small.

  Therefore, an object of the present invention is to provide a semiconductor laser and an optical semiconductor device that can improve the power of optical output.

  A semiconductor laser for achieving the above object includes a light active layer formed on a substrate, a formation layer formed on the active layer and having a diffraction grating region and a non-diffraction lattice region. A cladding layer formed on the formation layer, wherein the diffraction grating region is formed in a region away from the light emission end face, and the non-diffraction grating region is the emission end face. The ratio of the non-diffraction grating region on the emission end face side to the entire region of the formation layer is set to be a predetermined value.

  Here, a common electrode for injecting a current into the diffraction grating region and the non-diffraction lattice region may be further included.

  The rear end surface of the light opposite to the emission end surface may be provided with a non-reflective coating.

  The rear end surface of the light opposite to the emission end surface may be provided with a highly reflective coating.

  The exit end face may be provided with a non-reflective coating.

  The diffraction grating region may have a structure that shifts the phase of light.

  The semiconductor laser may include the semiconductor laser and the modulator of the semiconductor laser on the same substrate, and the light emitting end face on the modulator side may be provided with a non-reflective coating.

  The width of the optical waveguide corresponding to the diffraction grating region may be the same, and the width of the optical waveguide corresponding to the non-diffraction grating region may be formed so as to gradually increase toward the light exit end face. .

  According to the present invention, the power of light output can be improved.

It is a figure which shows the structural example of the semiconductor laser in 1st Embodiment. It is a figure which shows the example of a cross section of the semiconductor laser along the direction of optical output. It is a figure which shows an example of the relationship between an electric current and output power. It is a figure which shows the structure of a general semiconductor laser. FIG. 5 is a diagram illustrating a relationship between current and output power in the semiconductor laser of FIG. 4. It is a figure which shows a general semiconductor light source. It is a figure which shows an example of various laser characteristics in 1st Embodiment. It is a figure which shows the structural example of the semiconductor laser in 2nd Embodiment. It is a figure which shows the structural example of the semiconductor laser in 3rd Embodiment. It is a figure which shows the structural example of the semiconductor laser in 4th Embodiment. It is a figure which shows the structural example of the optical semiconductor device containing the semiconductor laser in 5th Embodiment. It is a figure which shows the structural example of the semiconductor laser in 6th Embodiment. It is a figure which shows the structural example of the optical semiconductor device containing the semiconductor laser in 7th Embodiment. It is a figure which shows the structural example of the optical semiconductor device containing the semiconductor laser in 8th Embodiment.

  Hereinafter, a plurality of embodiments of the present invention will be described. The semiconductor laser according to each embodiment is configured to include a diffraction grating and is an apparatus for outputting light using the diffraction grating.

<First Embodiment>
A first embodiment of the semiconductor laser of the present invention will be described with reference to FIGS.

[Configuration of semiconductor laser]
FIG. 1 is a diagram illustrating a configuration example of a semiconductor laser 10 according to the present embodiment.

  As shown in FIG. 1, the semiconductor laser 10 is formed on an n-type InP substrate 1 as a whole. On the substrate 1, a p-type including an active layer 2, a formation layer 3, and a contact layer is formed. The cladding layer 4 and the p-type electrode 5 are stacked in this order.

  A common electrode (not shown) is formed on the entire back surface of the substrate 1.

  In this semiconductor laser 10, the waveguide is shown by a ridge structure in which the cladding layer 4 is cut to the lower active layer 3, for example.

  In this embodiment, an example in which an InP substrate, for example, is applied as the substrate 1 is shown. In general, since the wavelength of light used for optical communication is in the 1.3 to 1.5 μm band, InP-based substrates having a band gap in the wavelength band are widely used.

  The active layer 2 includes, for example, an InGaAlAs strained quantum well layer. In this case, the active layer 2 has a quantum well structure that emits light having a photoluminescence spectroscopy peak (PL peak) of, for example, about 1.3 μm.

  The formation layer 3 has a diffraction grating. In this case, the period and depth of the diffraction grating are set so that the Bragg wavelength is about 1.3 μm, for example. The configuration of the formation layer 3 will be described in detail later. For example, InGaAsP is used as the material of the formation layer 3.

  The clad layer 4 is formed with the same width along the z-axis direction, which is the light output direction. In this case, for example, InP is used as the material of the cladding layer 4.

  The electrode 5 is shaped so as to cover the cladding layer 4.

  Both end faces 6 and 7 of the semiconductor laser 10, that is, the front end face 6 and the emission end face 7 are both provided with antireflection coating.

FIG. 2 is a cross-sectional view of the semiconductor laser 10 along the z-axis direction.
In the semiconductor laser 10 shown in FIG. 2, as shown in FIG. 1, the active layer 2, the formation layer 3, the cladding layer 4, and the electrode 5 are sequentially formed on the substrate 1. In FIG. 2, both end surfaces of the substrate 1, the active layer 2, the formation layer 3, and the cladding layer 4, that is, the front end surface 6 and the emission end surface 7 are shown. Further, the state in which the light output 11 is emitted from the emission end face 7 is shown.

  In this embodiment, as shown in FIG. 2, the formation layer 3 includes a region 31 in which a diffraction lattice is formed (hereinafter referred to as “diffraction lattice region”) and a diffraction lattice. Regions (hereinafter referred to as “non-diffraction lattice regions”) 32 and 33 are provided. A current is injected into these regions 31, 32 and 33 by the common electrode 5.

  The non-diffraction grating region 33 is formed on the front end face 6 side, and the non-diffraction grating area 32 is formed on the emission end face 7 side. The non-diffraction lattice region 32 functions as an active region into which current is injected. In this case, the lengths of the non-diffraction lattice regions 32 and 33 are L12 and L13, respectively.

  The diffraction grating region 31 is formed so as to be positioned between the two non-diffraction grating regions 32 and 33. In the diffraction grating region 31, a phase shift structure s is provided. In the example of FIG. 2, the phase in the diffraction grating region 31 is represented by a wavy line. The position of the phase shift structure s can be changed.

  Further, the shift amount of the phase shift structure s is set to π / 4, for example, in order to obtain a good single mode oscillation.

  In FIG. 2, the length of the diffraction grating region 31 is L11, and the entire length of the formation layer 3 is L1 (= L11 + L12 + L13). In this case, the resonator length of the semiconductor laser 10 is also L1.

[Method of manufacturing semiconductor laser]
Next, a method for manufacturing the semiconductor laser 10 in the present embodiment will be described with reference to FIGS.

  First, as shown in FIGS. 1 and 2, an active layer 2 having an InGaAlAs strained quantum well structure with a PL peak wavelength of about 1.3 μm and an InGaAsP formation layer 3 are grown on an n-InP substrate 1.

  Next, the InGaAsP formation layer 3 is wet or / and dry etched to form a diffraction grating having a Bragg wavelength of about 1.3 μm in the diffraction grating region 31 shown in FIG.

  Next, the p-InP clad layer 4 including the contact layer is grown to form a stacked structure of the semiconductor laser 10.

  Next, wet etching and / or dry etching is performed on portions of the contact layer excluding the portion where the electrode 5 is formed in FIG.

  Next, the formed cladding layer 4 is wet or / and dry etched up to the formation layer 3 to form a mesa waveguide having a ridge structure as shown in FIG. 1, and then an insulating film is formed by sputtering. Apply on the surface.

  Next, the electrode 5 is formed, and the back surface of the substrate 1 is polished to form an n-type common electrode on the back surface of the substrate 1. Thereafter, the semiconductor laser 10 having a resonator length of, for example, 400 μm, that is, L = 400 μm is manufactured by cleaving the semiconductor laser 10.

  Then, non-reflective coating is applied to both end faces 6 and 7 of the semiconductor laser 10 to complete. The antireflective coating can be realized, for example, by depositing a multilayer film of TiO2 and SiO2 on the laser end face.

[Relationship between current and output power]
Next, the relationship between the current injected into the semiconductor laser 10 and the output power will be described with reference to FIG. FIG. 3 is a diagram illustrating an example of the relationship between current and output power.

  In FIG. 3, for example, L1 = 400 μm (resonator length), L11 = 235 μm, L12 = 160 μm, and L13 = 5 μm. Further, the coupling coefficient κ of the diffraction grating is, for example, 35 cm −1, but is usually about κL11 = 0.7 to 2.5.

  In this case, since the ratio Ra (= L12 / L1) of L12 to L1 is 400 μm / 160 μm, Ra = 0.4 as shown in FIG.

  In the example of FIG. 3, the room temperature is set to 25 ° C. or 85 ° C., thereby obtaining a result corresponding to the given temperature.

  For example, when the room temperature is 25 ° C., the output power takes a value as shown by a broken line in FIG. 3 according to the value of the injected current. That is, the maximum output power is 36 mW when the current is 150 mA.

  On the other hand, when the room temperature is 85 ° C., the output power takes a value as shown by the solid line in FIG. 3 according to the value of the injected current. That is, the maximum output power is 21 mW when the current is 150 mA.

  It is known that a general semiconductor laser has a configuration as shown in FIG. FIG. 4 is a diagram showing a configuration of a general semiconductor laser 200.

  The semiconductor laser 200 is different from the first embodiment in that a diffraction grating is formed in the entire region of the formation layer 203. The formation layer 203 has a configuration having a phase shift structure s.

  In FIG. 4, the semiconductor laser 200 is also a p-InP including an n-InP substrate 201, an active layer 202 having an InGaAlAs strained quantum well structure, an InGaAsP formation layer 203, and a contact layer, similarly to the semiconductor laser 10 of FIG. A clad layer 204 and a p-type electrode 205 are provided. Further, non-reflective coating is applied to both end faces 206 and 207 of the semiconductor laser 200.

  In the case of such a semiconductor laser 200, the output power takes a value as shown in FIG. 5 according to the value of the injected current. FIG. 5 is a diagram showing the relationship between current and output power in a general semiconductor laser 200.

  In FIG. 5, conditions are given such that L1 = L11 = 400 μm (resonator length), room temperature = 25 ° C. or 85 ° C.

  For example, when the room temperature is 25 ° C., the output power is maximized at 150 mA, which is the same as in the case of FIG. 3 described above, but is 21 mW. Since it was 36 mW in FIG. 3, in the case of FIG. 3, 1.7 times as much output power as the case of FIG. 5 is obtained.

  When the room temperature is 85 ° C., the output power is maximized at 150 mA, which is the same as in FIG. 3 described above, but is 13.5 mW. Since it was 24 mW in FIG. 3, the output power in the case of FIG. 3 is about twice that in the case of FIG. Thus, the semiconductor laser 10 is suitable for application as an uncooled semiconductor laser that does not require temperature adjustment.

  From the above, it can be seen that the semiconductor laser 10 of this embodiment can obtain a larger output power than the general semiconductor laser 200.

  In the case of FIG. 3, when the room temperature is 25 ° C., the injection current required to obtain an output power of 21 mW is about 94 mA, but in the case of FIG. 5, it is 150 mA. That is, the semiconductor laser 10 according to the present embodiment can reduce power consumption to about 60% as compared with the general semiconductor laser 200.

  In general, it is known that a semiconductor light source including a semiconductor optical amplifier (SOA) is configured as shown in FIG. FIG. 6 is a diagram showing a general semiconductor light source 300.

  As shown in FIG. 6, a semiconductor light source 300 includes a semiconductor optical amplifier 300B including a semiconductor laser 300A including a formation layer 303 including a diffraction grating region and a formation layer 303 including a non-diffraction lattice region on the same substrate 301. However, in this semiconductor light source 300, it is necessary to generate the passive waveguide 304. This is because the passive waveguide 304 is regrown after crystal growth of the active layer 302 when the semiconductor light source 300 is manufactured, which increases the manufacturing process and makes it complicated.

  In FIG. 6, the semiconductor laser 300 </ b> A also includes an active layer 302, a cladding layer 305, and an electrode 306. The semiconductor amplifier 300B also includes an active layer 302, a cladding layer 305, and an electrode 307.

  In FIG. 6, both end surfaces 308 and 309 of the semiconductor light source 300 are shown. An optical output 310 is also shown.

  In FIG. 6, the semiconductor laser 300A and the semiconductor optical amplifier 300B are shown as the same active layer 302. However, in order to optimize the semiconductor optical amplifier 300B, when the active layer 302 is generated separately from the active layer of the semiconductor optical amplifier 300B, a manufacturing process such as crystal regrowth or etching accompanying the generation is required. The manufacturing process becomes more complicated.

  On the other hand, in the semiconductor laser 10 of the present embodiment, the formation layer 303 composed of the diffraction grating region 31 and the non-diffraction grating regions 32 and 33 is formed, but it is not necessary to produce a core like the passive waveguide 304. .

  Further, in the semiconductor laser 10, it is only necessary to form one electrode 5 on the formation layer 304, so that the production is easier and the production cost is lower than in the case of the semiconductor light source 300 in which the two electrodes 306 and 307 are formed. To reduce.

  FIG. 7 is a diagram illustrating an example of various laser characteristics. The horizontal axis represents the ratio Ra (= L12 / L1) of L12 to L1, and the vertical axis represents ηf and SMGR.

  ηf represents a ratio {Pt / (Pf + Pt)} of the optical output power Pt from the emission end face 7 to the sum (Pf + Pt) of the optical output power from the front end 6 and the emission end face 7. SMGR shows a value of (g1−g0) / g0, where g0 is the threshold gain in the main mode and g1 is the threshold gain in the side mode.

  Ra is a value of the ratio (L12 / L1). That is, Ra is a ratio of the non-diffraction lattice region 32 on the emission end face 7 side to the entire regions 31, 32, 33 of the formation layer 3.

  For example, in the case of SMGR, when Ra is 0 to 0.8, the value shown by the broken line in FIG. That is, the value of SMGR is maximized when Ra is 0.2. And when Ra becomes larger than 0.2, the value of SMGR becomes smaller. In general, in the case of a semiconductor laser for a CW light source, the value of SMGR is set to be 0.1 or more. When the value of SMGR is 0.1, Ra is about 0.55.

  In the case of ηf, when Ra is 0 to 0.8, the value shown by the solid line in FIG. 7 is taken. That is, the value of ηf increases from about 0.5 to about 0.85 as the value of Ra increases.

  In FIG. 7, the points are measured values of ηf when Ra = 0, 0.2, and 0.4. These measured values are approximate to the theoretical value of ηf shown by the solid line in FIG.

  According to FIG. 7, it can be seen from the above-described values of ηf and SMGR that the light output can be increased while maintaining stable laser oscillation within the range of Ra = 0.2 to 0.55 (20% to 55%). . In particular, in the vicinity of Ra = 0.2, the value of ηf becomes the maximum as shown by the broken line in FIG. 7, so that the laser beam is more stable and has a larger output power.

  For example, when Ra = 0.02 to 0.1 (2% to 10%), the value of ηf is about 0.5 to 0.53, and the value of SMGR is about 0.72 to 0.75. . Therefore, the ratio of the light output power Pt from the emission end face 7 to the sum (Pf + Pt) of the light output power from the front end 6 and the emission end face 7 is set to 50% or more while the SMGR value is set to 0.1 or more. Can be made. Also in this case, the light output can be increased.

  As described above, according to the semiconductor laser 10 of the present embodiment, the diffraction grating region 31 is formed in the region away from the light emission end face 7 in the formation layer 3, and the non-diffractive lattice regions 32 and 33 are formed. The region 32 is formed on the emission end face 7 side. The ratio Ra of the non-diffraction lattice region 32 to the entire regions 31, 32, 33 of the formation layer 3 is set to be a predetermined value (for example, 2% to 55%). Thereby, the semiconductor laser 10 can obtain a larger output power. Furthermore, the semiconductor laser 10 can obtain a stable laser.

Second Embodiment
FIG. 8 is a diagram illustrating a configuration example of the semiconductor laser 10a of the second embodiment.

  The semiconductor laser 10A of FIG. 8 is different from the first embodiment in that embedded portions 21 and 22 are provided on both end faces of the active layer 2, the formation layer 3, and the cladding layer 4, respectively.

  For example, semi-insulating InP is used as the material of the embedded portions 21 and 22.

  Even if comprised in this way, the effect similar to 1st Embodiment is acquired.

<Third Embodiment>
Next, a semiconductor laser in which a diffraction grating is not provided with a phase shift structure will be described as an embodiment of the semiconductor laser.

  FIG. 9 is a diagram illustrating a configuration example of the semiconductor laser 10B of the third embodiment. The semiconductor laser 10B shown in FIG. 9 differs from the first embodiment in that the formation layer 3A includes a diffraction grating region 31A having no phase shift structure. In this case, in the diffraction grating region 31A, the period of the diffraction grating is uniform.

  Even if comprised in this way, the effect similar to 1st Embodiment is acquired.

<Fourth embodiment>
Next, as an embodiment of the semiconductor laser, a semiconductor laser in which a highly reflective coating is applied to the front end of the semiconductor laser will be described.

  FIG. 10 is a diagram illustrating a configuration example of a semiconductor laser 10C according to the fourth embodiment. FIG. 10 is different from FIG. 2 only in that the semiconductor laser has a front end 6A. In this case, a highly reflective coating is applied to the front end 6A. The highly reflective coating can be realized, for example, by depositing a multilayer film of Si and SiO2 on the laser end face.

  With this configuration, it is possible to reduce the light output 11 emitted from the front end face 6A of the semiconductor laser 10C and obtain a larger power of the light output 11.

<Fifth Embodiment>
FIG. 11 is a diagram illustrating a configuration example of a semiconductor laser 10D according to the fifth embodiment. FIG. 11 is different from FIG. 10 in that the formation layer 3A is provided with a diffraction grating region 31A having no phase shift structure. In this case, in the diffraction grating region 31A, the period of the diffraction grating is uniform.

  Even if comprised in this way, the effect similar to 4th Embodiment is acquired.

<Sixth Embodiment>
Next, a semiconductor laser (optical semiconductor device) in which an electroabsorption modulator is also integrated on the same substrate will be described as an embodiment of the semiconductor laser.

  FIG. 12 is a cross-sectional view showing a configuration example of the semiconductor laser 10E of the sixth embodiment. 11 differs from FIG. 2 in that the modulator is also integrated on the substrate 11, and therefore the modulator will be mainly described.

  In FIG. 12, a semiconductor laser 10E includes an electroabsorption layer 17, an etching stop layer 18, an InGaAsP formation layer 14, and a p-type electrode 19 on an n-InP substrate 11 as a modulator.

  The electroabsorption layer 17 has a quantum well structure that emits light having a PL peak in the vicinity of, for example, 1.24 μm.

  Further, the semiconductor laser 10E includes an InGaAsP core layer 17 and an etching strap layer 18.

  As a laser device, the semiconductor laser 10E has an active layer 12 having an InGaAlAs strained quantum well structure, an InGaAsP formation layer 13, a p-InP clad layer 14 including a contact layer, and a p-type on an n-InP substrate 11. The electrode 15 is provided. The configuration of these laser devices is the same as that of the semiconductor laser 10 of the first embodiment.

  Further, both end faces 16 and 20 of the semiconductor laser 10E are provided with non-reflective coating.

  The semiconductor laser 10E of this embodiment is suitable as a light source with high output and low power consumption.

<Seventh embodiment>
Next, a semiconductor laser (optical semiconductor device) in which a Mach-Zehnder type modulator is also integrated will be described as an embodiment of the semiconductor laser.

FIG. 13 is a plan view showing a configuration example of the semiconductor laser 10F of the seventh embodiment.
In FIG. 13, a semiconductor laser 10F has a laser device 31 and a modulator 32 integrated on the same substrate. In this case, the modulator 32 has a Mach-Zehnder type waveguide 33 having two arms. The modulator 32 changes the intensity of light according to the voltage applied to each arm.

  The laser device 31 is configured similarly to the laser device of the sixth embodiment. In FIG. 13, the diffraction grating 312 has a phase shift structure s.

  Even if comprised in this way, it is suitable as a light source of high output and low power consumption.

<Eighth Embodiment>
Next, a semiconductor laser (optical semiconductor device) 10G in which the width of the optical waveguide is changed will be described as an embodiment of the semiconductor laser.

  FIG. 14 is a diagram illustrating a configuration example of the semiconductor laser 10G according to the eighth embodiment, in which (a) a plane of the semiconductor laser 10G and (b) a cross section of the semiconductor laser 10G are illustrated. 14 differs from FIGS. 1 and 2 only in the shape of the optical waveguide as viewed from above.

  14A and 14B, the width of the optical waveguide corresponding to the diffraction grating region 31 is the same, and the width of the optical waveguide corresponding to the non-diffraction grating region 31 is directed toward the light exit end face 7. It is formed so as to increase gradually.

  In this case, in addition to the effects of the first embodiment, the mesa width of the laser semiconductor 10G gradually increases toward the emission end face 7, whereby the region into which current is injected increases and the optical output 11 becomes larger. Further, the reflected light from the front end face 6 is reduced, and the resistance to the return light can be increased. The shape of the width of the optical waveguide according to the eighth embodiment may be applied to the first to seventh embodiments.

<Modification>
In the above, the semiconductor laser capable of realizing a high output has been described with reference to the first to eighth embodiments. However, other shapes of configurations can be applied.

  In the semiconductor laser of each embodiment, the material of the active layer is InGaAlAs, but other materials such as InGaAsP and GaInNAs may be applied.

  Or although the case where the InP substrate 31 is used has been described, for example, a GaAs, sapphire substrate, silicon substrate, or other semiconductor substrate can be applied.

  The length of the laser is 400 μm, but can be changed. Although an n-type substrate is shown as an example, a p-type or insulating substrate may be applied. For the wavelength range of light, only an example in the vicinity of 1.3 μm is shown, but the same effect can be obtained for light in other wavelength bands, for example, near 1.55 μm.

  The diffraction grating layer of each embodiment or the like is formed at a position that is substantially at the center in the formation layer. For example, it may be formed at a position that is shifted from the center in the formation layer to the front end face side. Alternatively, it may be formed at a position shifted from the center in the formation layer to the emission end face side.

  Although the waveguide structure has been described as a ridge waveguide structure, it may be a high mesa structure or a buried structure.

DESCRIPTION OF SYMBOLS 10 Semiconductor laser 1 Substrate 2 Active layer 3 Formation layer 4 Cladding layer 5 Electrode 31 and 33 Non-diffraction lattice region 32 Diffraction lattice region

Claims (8)

An active layer of light formed on the substrate;
A formation layer formed on the active layer and having a diffraction lattice region and a non-diffraction lattice region;
A clad layer formed on the formation layer,
In the formation layer, the diffraction grating region is formed in a region away from the light emission end face, and the non-diffraction grating region is formed on the emission end face side,
The ratio of the non-diffraction grating region on the emission end face side to the entire region of the formation layer is set to be a predetermined value.
Semiconductor laser.   The semiconductor laser according to claim 1, further comprising a common electrode for injecting a current into the diffraction grating region and the non-diffraction lattice region.   The semiconductor laser according to claim 1, wherein a front end face of light opposite to the emission end face is provided with a non-reflective coating.   The semiconductor laser according to claim 1, wherein a front end face of light opposite to the emission end face is provided with a highly reflective coating.   The semiconductor laser according to claim 1, wherein the emitting end face is provided with a non-reflective coating.   The semiconductor laser according to claim 1, wherein the diffraction grating region has a structure that shifts a phase of light. Including the semiconductor laser according to any one of claims 1 to 6 and a modulator of the semiconductor laser on the same substrate;
The light emitting end face of the modulator side is provided with a non-reflective coating,
Optical semiconductor device.   The width of the optical waveguide corresponding to the diffraction grating region is the same, and the width of the optical waveguide corresponding to the non-diffraction grating region is formed so as to gradually increase toward the light exit end face. The semiconductor laser according to any one of claims 1 to 6.

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