Semiconductor laser

Abstract

The utility model provides a semiconductor laser which is provided with an epitaxial layer. The epitaxial layer comprises a p-type waveguide layer, a p-type cladding and an ohmic contact layer. And a grating layer is arranged in the p-type cladding. Wherein the doping concentration of the material of the grating layer is smaller than or equal to the doping concentration of the material of the p-type cladding, and the doping concentration of the p-type cladding is larger than the doping concentration of the p-type waveguide layer. According to the semiconductor laser, the doping concentration of the grating layer is reduced, the absorption level of free carriers is reduced, free carrier absorption is reduced, the band gap difference between the grating layer and the p-type cladding is utilized, the loss type coupling grating is formed, and single longitudinal mode lasing of the semiconductor laser is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of semiconductor chips, and in particular to a semiconductor laser. Background Art

[0002] Distributed Feedback Laser (DFB) has a built-in Bragg Grating and is an edge-emitting semiconductor laser. DFB mainly uses semiconductor materials as the medium, including gallium antimonide (GaSb), gallium arsenide (GaAs), indium phosphide (Inp), zinc sulfide (ZnS), etc. The biggest feature of DFB is that it has very good monochromaticity (i.e. spectral purity). Its line width can generally be within 1MHz, and it has a very high side mode suppression ratio (SMSR), which can be as high as 40-50dB or more.

[0003] Specifically, the Bragg grating built into the DFB can be set as a uniform grating or a phase-shifted grating. In the refractive index coupling type DFB based on uniform grating, its advantage is that the holographic method can be used to achieve low-cost grating preparation, and the technology is mature. The disadvantage is that the two modes of the grating will compete, resulting in the instability of the single longitudinal mode lasing, resulting in a decrease in the yield of the device. In the refractive index coupling type DFB based on phase-shifted grating, its advantage is that the degeneracy of the mode can be eliminated to achieve stable single longitudinal mode lasing. The disadvantage is that it cannot be achieved by a holographic method, and generally uses electron beam exposure technology, which is inefficient and costly.

[0004] The epitaxial layer of the semiconductor laser has a multilayer structure, and there are two types of band gap distribution: Figure 1a The intermediate layer shown is a narrow bandgap material and Figure 1b The middle layer shown is a wide bandgap material. Figure 1a and Figure 1b As shown, holes with slower mobility are more easily confined at the valence band step. Therefore, in the prior art, a highly doped grating layer is generally used to flatten the band gap and solve the problem of valence band steps. However, the highly doped grating layer will bring additional free carrier absorption, resulting in a decrease in device efficiency. Utility Model Content

[0005] Based on this, the present application provides a semiconductor laser, which adopts a refractive index coupled lossy grating structure, utilizes the valence band step to limit the carrier injection in some areas, forms a loss area, breaks through the degeneracy of the two modes, and realizes single longitudinal mode lasing.

[0006] The present application provides a semiconductor laser, comprising: a substrate and an epitaxial layer arranged on the substrate, wherein the epitaxial layer comprises a p-type waveguide layer, a p-type cladding layer and an ohmic contact layer which are stacked;

[0007] A grating layer is provided in the p-type cladding layer;

[0008] Wherein, the doping concentration of the grating layer is less than or equal to the doping concentration of the p-type cladding layer;

[0009] The doping concentration of the p-type cladding layer is greater than the doping concentration of the p-type waveguide layer.

[0010] In one embodiment, the doping concentration of the grating layer is less than 1×10 17 cm -3 .

[0011] In one embodiment, the doping concentration of the p-type cladding layer is less than 1×10 17 cm -3 .

[0012] In one embodiment, the p-type cladding layer includes a first p-type cladding layer and a second p-type cladding layer respectively disposed on both sides of the grating layer from bottom to top; the first p-type cladding layer has a surface in contact with the p-type waveguide layer; the second p-type cladding layer has a surface in contact with the ohmic contact layer;

[0013] The doping concentration of the first p-type cladding layer is less than the doping concentration of the second p-type cladding layer;

[0014] The doping concentration of the grating layer is less than the doping concentration of the second p-type cladding layer.

[0015] In one embodiment, the grating layer includes a plurality of grating strips arranged at periodic intervals, the ratio of one grating strip to one grating period is the grating duty cycle, and the grating duty cycle is less than or equal to 50%.

[0016] In one embodiment, the grating layer is an m-order grating, and the grating duty cycle of the m-order grating is k*(1 / 2m), wherein m is a positive integer, k is an odd number, and k<2m.

[0017] In one embodiment, the semiconductor laser has a front cavity surface for emitting light and a rear cavity surface opposite to the front cavity surface;

[0018] In a plane perpendicular to the stacking direction of the epitaxial layer, the grating layer has two or more grating segments along the direction from the rear cavity surface to the front cavity surface;

[0019] Wherein, the grating duty ratio of the grating segment close to the front cavity surface is greater than or equal to the grating duty ratio of the grating segment close to the rear cavity surface.

[0020] In one embodiment, the semiconductor laser has a front cavity surface for emitting light and a rear cavity surface opposite to the front cavity surface;

[0021] In a plane perpendicular to the stacking direction of the epitaxial layer, the grating layer has a first grating segment and a second grating segment along a direction from the rear cavity surface to the front cavity surface;

[0022] The grating duty cycle in the second grating segment is greater than the grating duty cycle in the first grating segment.

[0023] In one embodiment, the semiconductor laser has a front cavity surface for emitting light and a rear cavity surface opposite to the front cavity surface;

[0024] In a plane perpendicular to the stacking direction of the epitaxial layer, the grating layer has a first grating segment, a second grating segment and a third grating segment along the direction from the rear cavity surface to the front cavity surface;

[0025] The grating duty cycle in the second grating segment is greater than the grating duty cycle in the first grating segment, and the grating duty cycle in the third grating segment is greater than the grating duty cycle in the second grating segment.

[0026] In one embodiment, the semiconductor laser has a front cavity surface for emitting light and a rear cavity surface opposite to the front cavity surface;

[0027] In a plane perpendicular to the stacking direction of the epitaxial layer, the grating layer has a first grating segment, a second grating segment and a third grating segment along the direction from the rear cavity surface to the front cavity surface;

[0028] In the direction from the rear cavity surface to the front cavity surface, the length of the second grating segment is greater than the sum of the length of the first grating segment and the length of the third grating segment;

[0029] The doping concentration of the second grating segment is greater than the doping concentration of the first grating segment, and the doping concentration of the third grating segment is greater than the doping concentration of the second grating segment.

[0030] In one embodiment, the refractive index of the p-type cladding layer is n1, the refractive index of the grating layer is n2,

[0031] The percentage of the refractive index difference between the p-type cladding layer and the grating layer is |n1-n2| / n1, and |n1-n2| / n1 is less than 10%.

[0032] The present application has at least the following advantages or beneficial effects:

[0033] 1. The semiconductor laser provided by the present application has a grating layer in the p-type cladding. The doping concentration of the grating layer material is less than or equal to the doping concentration of the p-type cladding material, and the doping concentration of the p-type cladding is greater than the doping concentration of the p-type waveguide layer. The semiconductor laser provided by the present application reduces the doping concentration on the basis of the refractive index coupled grating structure, utilizes the valence band step, limits the carrier injection of a part of the area (grating layer), forms a loss area, and transforms the refractive index coupled grating into a refractive index coupled + loss grating, breaking through the degeneracy of the dual mode and realizing single longitudinal mode lasing.

[0034] 2. In the embodiment provided in the present application, the doping concentration of the grating layer is ≤ the doping concentration of the p-type cladding layer, and the doping concentration of the grating layer is set to be less than 1×10 17 cm -3 The doping concentration of the grating layer can even be set to 0, that is, no doping is done in the grating layer. The doping concentration of the grating layer becomes lower, the concentration of freely movable carriers decreases, and the freely movable carriers are easily confined in the steps formed by the band gap difference between the grating layer and the p-type cladding layer, further reducing the free carrier absorption level and reducing free carrier absorption.

[0035] 3. In the semiconductor laser provided in the present application, the doping concentration of the first p-type cladding layer and the doping concentration of the grating layer are both lower than the doping concentration of the second p-type cladding layer. The higher doping concentration of the second p-type cladding layer is beneficial to reducing the series resistance and improving the device performance.

[0036] 4. The semiconductor laser provided in the present application increases the current injection area and reduces the loss by adjusting the grating duty cycle, thereby improving the device performance and ensuring the electro-optical conversion efficiency.

[0037] 5. The semiconductor laser provided by the present application is provided with a non-uniform grating layer, and the specific non-uniformity is reflected in that the grating duty ratios of the two grating segments are different in the direction from the rear cavity surface to the front cavity surface. On the one hand, the grating duty ratio of the first grating segment is relatively small, which can ensure the overall injection current of the semiconductor laser. On the other hand, the grating duty ratio of the second grating segment is relatively large, which can avoid the excessive temperature of the front cavity surface caused by the large current near the front cavity surface, thereby reducing the damage to the front cavity surface.

[0038] 6. The semiconductor laser provided in the present application divides the grating layer into three sections, and the doping concentrations of the first grating section, the second grating section, and the third grating section can be set to gradually increase. The first grating section is closer to the rear cavity surface, the third grating section is closer to the front cavity surface, and the second grating section is located between the first grating section and the third grating section. The first grating section has the lowest doping concentration, the largest bandgap step, the strongest carrier transport blocking effect, and forms a stronger loss-coupled grating, which ensures the stable lasing of the single longitudinal mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0040] Figure 1a The energy band diagram of the intermediate layer provided in the prior art is a narrow band gap material;

[0041] Figure 1b The energy band diagram of the intermediate layer provided in the prior art is a wide band gap material;

[0042] Figure 2 A schematic diagram of the structure of a semiconductor laser provided in one embodiment of the present application;

[0043] Figure 3 A schematic diagram of the structure of a semiconductor laser provided in another embodiment of the present application;

[0044] Figure 4 A schematic diagram of the structure of a semiconductor laser provided in yet another embodiment of the present application.

[0045] Icons: substrate 1, epitaxial layer 10, n-type cladding layer 12, n-type waveguide layer 13, quantum well layer 14, p-type waveguide layer 15, p-type cladding layer 16, grating layer 17, grating strips 17a, ohmic contact layer 18;

[0046] A first p-type cladding layer 161 and a second p-type cladding layer 162;

[0047] A first grating segment 171 , a second grating segment 172 , and a third grating segment 173 . DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0049] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0050] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0051] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the utility model product is usually placed when in use. They are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0052] In addition, the terms "horizontal", "vertical" and the like do not mean that the components are required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0053] In the description of this application, it should also be noted that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0054] According to the different band gaps, semiconductor lasers can be divided into: Figure 1a The narrow bandgap semiconductor laser shown and Figure 1b The wide bandgap laser shown. Figure 1a and Figure 1b It can be seen that holes are more easily confined at the valence band step. Therefore, in the prior art, a highly doped grating layer is generally used to flatten the band gap and solve the problem of the valence band step. However, the highly doped grating layer will bring additional free carrier absorption, resulting in a decrease in the efficiency of the device. Based on this, the present application provides a semiconductor laser, which adopts a refractive index coupled lossy grating structure, utilizes the valence band step, limits the carrier injection in some areas, forms a loss area, breaks through the degeneracy of the dual mode, and realizes single longitudinal mode lasing.

[0055] See also Figure 2-Figure 4The present application provides a semiconductor laser, comprising: a substrate 1 and an epitaxial layer 10 disposed on the substrate 1. The epitaxial layer 10 includes an n-type cladding layer 12, an n-type waveguide layer 13, a quantum well layer 14, a p-type waveguide layer 15, a p-type cladding layer 16 and an ohmic contact layer 18 arranged in sequence from bottom to top. A grating layer 17 is arranged in the p-type cladding layer 16. The grating layer 17 is a refractive index coupled grating structure. The doping concentration of the grating layer 17 is less than or equal to the doping concentration of the p-type cladding layer 16. The doping concentration of the p-type cladding layer 16 is greater than the doping concentration of the p-type waveguide layer 15.

[0056] In this embodiment, by reducing the doping concentration of the grating layer 17, the absorption level of free carriers is reduced, and the free carrier absorption is reduced. By utilizing the band gap difference between the grating layer 17 and the p-type cladding 16, a lossy coupled grating is formed to achieve single longitudinal mode lasing of the semiconductor laser.

[0057] In one embodiment, the doping concentration of the grating layer 17 is less than 1×10 17 cm -3 .

[0058] In this embodiment, the doping concentration of the grating layer 17 is less than or equal to the doping concentration of the p-type cladding layer 16, and the doping concentration of the grating layer 17 is set to be less than 1×10 17 cm -3 The doping concentration of the grating layer 17 can even be set to 0, that is, no doping is done in the grating layer 17. The doping concentration of the grating layer becomes lower, the concentration of freely movable carriers decreases, and the freely movable carriers are easily confined in the steps formed by the band gap difference between the grating layer and the p-type cladding layer 16, further reducing the free carrier absorption level and reducing free carrier absorption.

[0059] In one embodiment, the doping concentration of the p-type cladding layer 16 is less than 1×10 17 cm -3 .

[0060] In this embodiment, the doping concentration of the grating layer 17 is ≤ the doping concentration of the p-type cladding layer 16 < 1×10 17 cm -3 , that is, the doping concentration of the grating layer 17 and the p-type cladding layer 16 is limited to less than 1×10 17 cm -3 , when the doping concentration of the grating layer 17 and the doping concentration of the p-type cladding layer 16 are both less than 1×10 17 cm -3 When the band gap difference between the two is greater, it is easier to form a step that restricts the movement of carriers, thereby making it easier to reduce the free carrier absorption level and reduce the free carrier absorption.

[0061] In some embodiments, the p-type cladding layer 16 may be configured to be gradually doped, such as gradually doped in a stacking direction from bottom to top or gradually doped in a cavity length direction from a rear cavity surface to a front cavity surface.

[0062] In one embodiment, Figure 2 As shown, the p-type cladding layer 16 includes a first p-type cladding layer 161 and a second p-type cladding layer 162 respectively arranged on both sides of the grating layer 17 from bottom to top. The first p-type cladding layer 161 has a surface in contact with the p-type waveguide layer 15. The second p-type cladding layer 162 has a surface in contact with the ohmic contact layer 18. The doping concentration of the first p-type cladding layer 161 is less than the doping concentration of the second p-type cladding layer 162. The doping concentration of the grating layer 17 is less than the doping concentration of the second p-type cladding layer 162.

[0063] Specifically, the doping concentration of the first p-type cladding layer 161 and the doping concentration of the grating layer 17 may not be limited. In some embodiments, the doping concentration of the first p-type cladding layer 161 is less than or equal to the doping concentration of the grating layer 17 .

[0064] In this embodiment, the doping concentration of the first p-type cladding layer 161 and the doping concentration of the grating layer 17 are both lower than the doping concentration of the second p-type cladding layer 162 . The higher doping concentration of the second p-type cladding layer 162 is beneficial to reducing the series resistance and improving the device performance.

[0065] In one embodiment, the grating layer 17 includes a plurality of grating strips 17a arranged at periodic intervals, the ratio of one grating strip 17a to one grating period is the grating duty cycle, and the grating duty cycle is less than or equal to 50%.

[0066] In one embodiment, the grating duty cycle is 15%-40%. In another embodiment, the grating duty cycle can be 5%-50%, or even lower than 5%. The adjustment of the grating duty cycle can increase current injection. In this embodiment, by adjusting the grating duty cycle, the current injection area is increased, the loss is reduced, and the device performance is improved.

[0067] In one embodiment, the grating layer 17 is an m-order grating, and the grating duty cycle of the m-order grating is k*(1 / 2m), wherein m is a positive integer, k is an odd number, and k<2m.

[0068] For example, m=1, k=1, the grating duty cycle is 50%; m=2, k=1, the grating duty cycle is 25%; m=3, k=1, the grating duty cycle is 16.7%; m=3, k=3, the grating duty cycle is 50%; m=4, k=1, the grating duty cycle is 12.5%; m=4, k=3, the grating duty cycle is 37.5%; m=5, k=1, the grating duty cycle is 10%; m=5, k=3, the grating duty cycle is 30%; m=5, k=5, the grating duty cycle is 50%; m=6, k=1, the grating duty cycle is 8.3%; m=6, k=3, the grating duty cycle is 25%; m=6, k=5, the grating duty cycle is 41.7%.

[0069] In this embodiment, the specific adjustment method of the grating duty cycle can be changed in combination with the order of the grating in the grating layer. For example, the grating duty cycle of the m-order grating is k*(1 / 2m) or 1-k*(1 / 2m) (equivalent to k*(1 / 2m) in technical effect), and the grating duty cycle of the semiconductor device is selected to be less than or equal to 50%.

[0070] See also Figure 3 In one embodiment, the single-mode semiconductor laser has a front cavity surface for emitting light and a rear cavity surface opposite to the front cavity surface. In a plane perpendicular to the stacking direction of the epitaxial layer 10, the grating layer 17 has a first grating segment 171 and a second grating segment 172 along the direction from the rear cavity surface to the front cavity surface. For the first-order grating, the grating duty cycle in the second grating segment 172 is greater than the grating duty cycle in the first grating segment 171, so the grating coupling coefficient is also higher.

[0071] Specifically, along the cavity length direction, the length ratio of the first grating segment 171 to the second grating segment 172 can be set to be between 6:4 and 9:1, for example, the length ratio of the first grating segment 171 to the second grating segment 172 is 8:2.

[0072] In this embodiment, a non-uniform grating layer 17 is provided, and the specific non-uniformity is reflected in that the grating duty ratios of the two grating segments are different in the direction from the rear cavity surface to the front cavity surface. The second grating segment 172 is closer to the front cavity surface, and the first grating segment 171 is closer to the rear cavity surface. For the first-order grating, the grating duty ratio of the second grating segment 172 is greater than the grating duty ratio of the first grating segment 171, and a higher grating coupling coefficient is obtained. On the one hand, the grating duty ratio of the first grating segment 171 is relatively small, which can ensure the overall injection current of the semiconductor laser. On the other hand, the grating duty ratio of the second grating segment 172 is relatively large, which can avoid the excessive temperature of the front cavity surface caused by the large current near the front cavity surface, thereby reducing the damage to the front cavity surface.

[0073] See also Figure 4In one embodiment, the single-mode semiconductor laser has a front cavity surface for emitting light and a rear cavity surface opposite to the front cavity surface. In a plane perpendicular to the stacking direction of the epitaxial layer 10, the grating layer 17 has a first grating segment 171, a second grating segment 172 and a third grating segment 173 in a direction from the rear cavity surface to the front cavity surface. The grating duty ratio in the second grating segment 172 is greater than the grating duty ratio in the first grating segment 171, and the grating duty ratio in the third grating segment 173 is greater than the grating duty ratio in the second grating segment 172.

[0074] In one embodiment, in the direction from the rear cavity surface to the front cavity surface, the length ratio of the first grating segment 171: the second grating segment 172: the third grating segment 173 can be set to 2.5:5:2.5, 2:6:2, 1.5:7:1.5, 1:8:1, or 0.5:9:0.5.

[0075] In this embodiment, a non-uniform grating layer 17 is provided, and the specific non-uniformity is reflected in the direction of the cavity length along the direction of the back cavity surface pointing to the front cavity surface, and the grating duty ratios of the three grating segments are different. The first grating segment 171 is closer to the back cavity surface, the third grating segment 173 is closer to the front cavity surface, and the second grating segment 172 is located between the first grating segment 171 and the third grating segment 173. For the first-order grating, the grating duty ratios of the first grating segment 171, the grating duty ratios of the second grating segment 172, and the grating duty ratios of the third grating segment 173 gradually increase to obtain a higher grating coupling coefficient. On the one hand, the grating duty ratios of the first grating segment 171 and the grating duty ratios of the second grating segment 172 are relatively small, which can ensure the overall injection current of the semiconductor laser. On the other hand, the grating duty ratio of the third grating segment 173 is relatively large, which can avoid the excessive temperature of the front cavity surface caused by the large current near the front cavity surface, thereby reducing the damage to the front cavity surface. From another perspective, the second grating segment 172 can be used as the core grating layer of the entire grating layer 17, the second grating segment 172 accounts for 50%-95% of the entire cavity length, the grating duty cycle in the second grating segment 172 is 15%-40%, and the doping concentration of the second grating segment 172 is less than 1×10 17 cm -3 , which can ensure the light regulation performance of the entire semiconductor device.

[0076] In one embodiment, a single-mode semiconductor laser has a front cavity surface for emitting light and a rear cavity surface opposite to the front cavity surface. In a plane perpendicular to the stacking direction of the epitaxial layer 10, the grating layer 17 has a first grating segment 171, a second grating segment 172 and a third grating segment 173 along the direction from the rear cavity surface to the front cavity surface. In the direction from the rear cavity surface to the front cavity surface, the length of the second grating segment 172 is greater than the sum of the length of the first grating segment 171 and the length of the third grating segment 173. The doping concentration of the second grating segment 172 is greater than the doping concentration of the first grating segment 171, and the doping concentration of the third grating segment 173 is greater than the doping concentration of the second grating segment 172.

[0077] In this embodiment, the grating layer is divided into three sections, and the doping concentrations of the first grating section 171, the second grating section 172 and the third grating section 173 can be set to gradually increase. In the above embodiment, a non-uniform grating layer 17 is set, and the specific non-uniformity is reflected in the direction from the rear cavity surface to the front cavity surface, and the doping concentrations of the three grating sections are different. The first grating section 171 is closer to the rear cavity surface, the third grating section 173 is closer to the front cavity surface, and the second grating section 172 is located between the first grating section 171 and the third grating section 173. The first grating section 171 has the lowest doping concentration, the largest band gap step, the strongest carrier transport blocking effect, and forms a stronger loss-coupled grating, which ensures the stable lasing of the single longitudinal mode.

[0078] In one embodiment, the refractive index of the p-type cladding layer 16 is n1, the refractive index of the grating layer 17 is n2, and the percentage of the refractive index difference between the p-type cladding layer 16 and the grating layer 17 is |n1-n2| / n1, and |n1-n2| / n1<10%.

[0079] In this embodiment, the grating coupling coefficient is further improved by increasing the percentage of the refractive index difference between the grating layer 17 and the p-type cladding layer 16. The refractive index difference (n1-n2) between the grating layer 17 and the p-type cladding layer 16 can be a positive value or a negative value. The greater the refractive index difference between the grating layer 17 and the p-type cladding layer 16, the greater the grating coupling coefficient.

[0080] In one embodiment, the thickness of the grating layer 17 is less than 100 nm. In the prior art, the thickness of the grating layer is relatively thin, about a few nm to tens of nm, and the thickness of the grating layer is less than 50 nm. In this embodiment, the thickness of the grating layer 17 is more than doubled. By increasing the thickness of the grating layer 17, the grating coupling coefficient can be further improved.

[0081] The material selection of the semiconductor laser involved in any of the above embodiments of the present application can be gallium arsenide or indium phosphide. For example, the material of the semiconductor laser is gallium arsenide, the substrate 1 can be set to n-type gallium arsenide, the n-type cladding 12 can be set to AlGaAs, the n-type waveguide layer 13 can be set to AlGaAs, the quantum well layer 14 can be set to InGaAs, the p-type waveguide layer 15 can be set to AlGaAs, the p-type cladding 16 can be set to AlGaAs and the ohmic contact layer 18 can be set to GaAs, and the grating layer 17 in the p-type cladding 16 can be set to GaAs. The p-type waveguide layer 15 can be doped with C material, the p-type cladding 16 can be doped with C material, and the grating layer 17 can be doped with C material.

[0082] For another example, the material of the semiconductor laser is an indium phosphide material, the substrate 1 can be set to n-type indium phosphide, the n-type cladding 12 can be set to Inp, the n-type waveguide layer 13 can be set to InGaAsp, the quantum well layer 14 can be set to InGaAsp, the p-type waveguide layer 15 can be set to InGaAsp, the p-type cladding 16 can be set to Inp, and the ohmic contact layer 18 can be set to InGaAs, and the grating layer 17 in the p-type cladding 16 can be set to InGaAsp. The p-type waveguide layer 15 can be doped with Zn material, the p-type cladding 16 can be doped with Zn material, and the grating layer 17 can be doped with Zn material.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A semiconductor laser, characterized in that: include: A substrate (1) and an epitaxial layer (10) arranged on the substrate (1), wherein the epitaxial layer (10) comprises a p-type waveguide layer (15), a p-type cladding layer (16) and an ohmic contact layer (18) which are stacked; A grating layer (17) is provided in the p-type cladding layer (16); Wherein, the doping concentration of the grating layer (17) is less than or equal to the doping concentration of the p-type cladding layer (16); The doping concentration of the p-type cladding layer (16) is greater than the doping concentration of the p-type waveguide layer (15).

2. The semiconductor laser according to claim 1, characterized in that The doping concentration of the grating layer (17) is less than 1×10 17 cm -3 .

3. The semiconductor laser according to claim 2, characterized in that The doping concentration of the p-type cladding layer (16) is less than 1×10 17 cm -3 .

4. The semiconductor laser according to claim 1, characterized in that The p-type cladding layer (16) comprises a first p-type cladding layer (161) and a second p-type cladding layer (162) which are respectively arranged on both sides of the grating layer (17) from bottom to top; the first p-type cladding layer (161) has a surface in contact with the p-type waveguide layer (15); and the second p-type cladding layer (162) has a surface in contact with the ohmic contact layer (18); The doping concentration of the first p-type cladding layer (161) is lower than the doping concentration of the second p-type cladding layer (162); The doping concentration of the grating layer (17) is lower than the doping concentration of the second p-type cladding layer (162).

5. The semiconductor laser according to claim 1, characterized in that The grating layer (17) comprises a plurality of grating strips (17a) arranged at periodic intervals, the ratio of one grating strip (17a) to one grating period is the grating duty cycle, and the grating duty cycle is less than or equal to 50%.

6. The semiconductor laser according to claim 5, characterized in that The grating layer (17) is an m-order grating, and the grating duty cycle of the m-order grating is k*(1 / 2m), wherein m is a positive integer, k is an odd number, and k<2m.

7. The semiconductor laser according to claim 5, characterized in that The semiconductor laser has a front cavity surface for emitting light and a rear cavity surface opposite to the front cavity surface; In a plane perpendicular to the stacking direction of the epitaxial layer (10), the grating layer (17) has two or more grating segments along the direction from the rear cavity surface to the front cavity surface; Wherein, the grating duty ratio of the grating segment close to the front cavity surface is greater than or equal to the grating duty ratio of the grating segment close to the rear cavity surface.

8. The semiconductor laser according to claim 7, characterized in that The semiconductor laser has a front cavity surface for emitting light and a rear cavity surface opposite to the front cavity surface; In a plane perpendicular to the stacking direction of the epitaxial layer (10), the grating layer (17) has a first grating segment (171) and a second grating segment (172) along a direction from the rear cavity surface to the front cavity surface; The grating duty cycle in the second grating segment (172) is greater than the grating duty cycle in the first grating segment (171).

9. The semiconductor laser according to claim 7, characterized in that: The semiconductor laser has a front cavity surface for emitting light and a rear cavity surface opposite to the front cavity surface; In a plane perpendicular to the stacking direction of the epitaxial layer (10), the grating layer (17) has a first grating segment (171), a second grating segment (172) and a third grating segment (173) along the direction from the rear cavity surface to the front cavity surface; The grating duty cycle in the second grating segment (172) is greater than the grating duty cycle in the first grating segment (171), and the grating duty cycle in the third grating segment (173) is greater than the grating duty cycle in the second grating segment (172).

10. The semiconductor laser according to claim 1, characterized in that The semiconductor laser has a front cavity surface for emitting light and a rear cavity surface opposite to the front cavity surface; In a plane perpendicular to the stacking direction of the epitaxial layer (10), the grating layer (17) has a first grating segment (171), a second grating segment (172) and a third grating segment (173) along the direction from the rear cavity surface to the front cavity surface; In the direction from the rear cavity surface to the front cavity surface, the length of the second grating segment (172) is greater than the sum of the length of the first grating segment (171) and the length of the third grating segment (173); The doping concentration of the second grating segment (172) is greater than the doping concentration of the first grating segment (171), and the doping concentration of the third grating segment (173) is greater than the doping concentration of the second grating segment (172).

11. The semiconductor laser according to claim 1, characterized in that The refractive index of the p-type cladding layer (16) is n1, the refractive index of the grating layer (17) is n2, The percentage of the refractive index difference between the p-type cladding layer (16) and the grating layer (17) is |n1-n2| / n1, and |n1-n2| / n1 is less than 10%.

Images