阅读说明：本技术 一种半导体激光器 (Semiconductor laser ) 是由 贾鹏 梁磊 陈泳屹 秦莉 宁永强 王立军 于 2020-11-18 设计创作，主要内容包括：本发明公开了一种半导体激光器,包括半导体PN结和设于半导体PN结且沿同列分布的表面有源布拉格反射光栅、脊形波导列阵、多模干涉波导和超对称列阵波导；表面有源布拉格反射光栅设于脊形波导列阵的一端,多模干涉波导的一端紧邻脊形波导列阵的另一端,超对称列阵波导紧邻多模干涉波导的另一端。该半导体激光器利用表面有源布拉格光栅提供波长可调谐的单频激光,利用脊形波导列阵进行增益放大,利用多模干涉波导进行相干耦合,最后利用超对称列阵波导进行二次横向模式选择和增益,实现高功率、窄线宽、波长可调谐的高光束质量激光。(The invention discloses a semiconductor laser, which comprises a semiconductor PN junction, and surface active Bragg reflection gratings, a ridge waveguide array, a multimode interference waveguide and a super-symmetric array waveguide which are arranged on the semiconductor PN junction and distributed along the same row; the surface active Bragg reflection grating is arranged at one end of the ridge waveguide array, one end of the multimode interference waveguide is close to the other end of the ridge waveguide array, and the super-symmetric array waveguide is close to the other end of the multimode interference waveguide. The semiconductor laser provides single-frequency laser with tunable wavelength by utilizing a surface active Bragg grating, performs gain amplification by utilizing a ridge waveguide array, performs coherent coupling by utilizing a multimode interference waveguide, and finally performs secondary transverse mode selection and gain by utilizing a super-symmetric array waveguide, thereby realizing high-power, narrow-linewidth and wavelength-tunable high-beam-quality laser.)

1. A semiconductor laser is characterized by comprising a semiconductor PN junction, and a surface active Bragg reflection grating (2), a ridge waveguide array (3), a multimode interference waveguide (4) and a super-symmetric array waveguide (5) which are arranged on the semiconductor PN junction and distributed along the same column;

the surface active Bragg reflection grating (2) is arranged at one end of the ridge waveguide array (3), one end of the multimode interference waveguide (4) is closely adjacent to the other end of the ridge waveguide array (3), and the ultra-symmetric array waveguide (5) is closely adjacent to the other end of the multimode interference waveguide (4).

2. A semiconductor laser as claimed in claim 1, characterized in that the multimode interference waveguide (4) is provided with a spatial modulation structure (6) for coherent combination of the laser light.

3. A semiconductor laser as claimed in claim 2 wherein the spatial modulation structure (6) comprises a plurality of cavities etched into the multi-mode interference waveguide (4) to increase the interface resistance.

4. A semiconductor laser as claimed in claim 1 wherein the multimode interference waveguide (4) comprises a plurality of inlet ends for connecting the ridge waveguide array (3) and a plurality of outlet ends for connecting the superpair array waveguides (2); all the inlet ends are uniformly distributed at one end of the ridge waveguide array (3).

5. A semiconductor laser as claimed in claim 1 wherein the super-symmetric arrayed waveguide (5) comprises a first super-symmetric arrayed waveguide (51) to achieve laser gain and a second super-symmetric arrayed waveguide (52) to achieve laser loss; the first super-symmetric arrayed waveguide (51) and the second super-symmetric arrayed waveguide (52) are arranged side by side.

6. A semiconductor laser according to any of claims 1 to 5, characterized in that the semiconductor PN junction comprises a N-type substrate layer (7), an N-layer cladding layer (8), an N-type waveguide layer (9), an active layer (10), a P-type waveguide layer (11), a P-type cladding layer (12) and a P-type highly doped layer (13) laid down in layers; the N-type substrate layer (7) is connected with an N electrode, and the P-type high-doped layer (13) is connected with a P electrode.

7. A semiconductor laser as claimed in claim 6 wherein the surface active Bragg reflection grating (2), the ridge waveguide array (3), the multimode interference waveguide (4) and the super-symmetric array waveguide (5) are provided in the P-type cladding (12) and the P-type highly doped layer (13).

8. The semiconductor laser of claim 6, wherein the semiconductor PN junction is elongated; the sum of the array-direction lengths of the surface active Bragg reflection grating (2), the ridge waveguide array (3), the multimode interference waveguide (4) and the super-symmetric array waveguide (5) is equal to the length of the semiconductor PN junction.

9. A semiconductor laser as claimed in claim 8 wherein the row width of both the ridge waveguide array (3) and the multimode interference waveguide (4) are equal to the width of the semiconductor PN junction.

10. The semiconductor laser according to claim 8, wherein both ends in a length direction of the semiconductor PN junction are provided with a high reflection film and an anti-reflection film, respectively.

Technical Field

The invention relates to the field of laser, in particular to a semiconductor laser.

Background

The semiconductor laser is a laser device which utilizes semiconductor materials as working substances, has the advantages of small volume, light weight, direct electro-optic conversion, high conversion efficiency, good beam quality, narrow laser line width and the like, and has wide application prospect in the fields of optical phased array laser radar, active detection and identification and the like.

The existing tunable high-beam-quality semiconductor laser mainly comprises a single-tube device for selecting waveguide modes, such as a master-controlled oscillator power amplifier, a tapered laser, a slab-coupled waveguide laser, a distributed feedback laser, a distributed Bragg reflection laser and the like.

Although high beam quality semiconductor lasers have made great progress in improving output power, beam quality, and optimizing spectral linewidth, various problems remain with each type of array device. For example, the master oscillator power amplifier and the tapered laser obtain high power output through a tapered semiconductor optical amplifier, but the optical aperture of the tapered amplifier is usually over 100 microns, which results in extremely low coupling efficiency with a single-mode optical fiber or a single-mode waveguide. For another example, a slab-coupled waveguide laser combines a ridge waveguide with a specially designed epitaxial structure to obtain high-light-quality laser, and the gain volume of the ridge waveguide is limited, so that it is difficult to achieve high-power output in watt level. For another example, the distributed feedback and distributed bragg reflector laser adopts a built-in grating structure to realize mode selection, but the design of the built-in grating structure is complex, the process difficulty is high, and the development cost is high.

In summary, it is an urgent need to solve the above-mentioned problems for those skilled in the art to provide a semiconductor laser that can achieve the balance between line width, beam quality and output power.

Disclosure of Invention

The invention provides a semiconductor laser which can provide laser with narrow line width, high beam quality and large output power to the outside.

In order to achieve the purpose, the invention provides a semiconductor laser, which comprises a semiconductor PN junction, and surface active Bragg reflection gratings, ridge waveguide arrays, multimode interference waveguides and super-symmetric array waveguides, wherein the surface active Bragg reflection gratings, the ridge waveguide arrays, the multimode interference waveguides and the super-symmetric array waveguides are arranged on the semiconductor PN junction and distributed along the same column;

the surface active Bragg reflection grating is arranged at one end of the ridge waveguide array, one end of the multimode interference waveguide is close to the other end of the ridge waveguide array, and the super-symmetric array waveguide is close to the other end of the multimode interference waveguide.

Preferably, a spatial modulation structure for realizing coherent combination of laser beams is arranged in the multi-mode interference waveguide.

Preferably, the spatial modulation structure comprises a plurality of cavities etched in the multi-mode interference waveguide for improving interface resistance.

Preferably, the multimode interference waveguide comprises a plurality of inlet ends for connecting the ridge waveguide array and a plurality of outlet ends for connecting the super-array waveguide array; all the inlet ends are uniformly distributed at one end of the ridge waveguide array.

Preferably, the super-symmetric arrayed waveguide comprises a first super-symmetric arrayed waveguide for realizing laser gain and a second super-symmetric arrayed waveguide for realizing laser loss; the first super-symmetric array waveguide and the second super-symmetric array waveguide are arranged side by side.

Preferably, the semiconductor PN junction comprises an N-type substrate layer, an N-layer cladding layer, an N-type waveguide layer, an active layer, a P-type waveguide layer, a P-type cladding layer and a P-type high-doping layer which are laid in a layered mode; the N-type substrate layer is connected with an N-pole electrode, and the P-type high-doping layer is connected with a P-pole electrode.

Preferably, the surface active bragg reflection grating, the ridge waveguide array, the multimode interference waveguide and the super-symmetric array waveguide are arranged on the P-type cladding and the P-type high-doped layer.

Preferably, the semiconductor PN junction is in a strip shape; the sum of the array length of the surface active Bragg reflection grating, the ridge waveguide array, the multimode interference waveguide and the super-symmetric array waveguide is equal to the length of the semiconductor PN junction.

Preferably, the row width of the ridge waveguide array and the multi-mode interference waveguide are equal to the width of the semiconductor PN junction.

Preferably, both ends of the semiconductor PN junction in the length direction are respectively provided with a high reflection film and an anti-reflection film.

Compared with the background technology, the semiconductor laser provided by the invention comprises a semiconductor PN junction, a surface active Bragg reflection grating, a ridge waveguide array, a multimode interference waveguide and a super-symmetric array waveguide.

In the semiconductor laser, four of a surface active Bragg reflection grating, a ridge waveguide array, a multimode interference waveguide and a super-symmetric array waveguide are arranged on a semiconductor PN junction and distributed along the same row. The surface active Bragg reflection grating is arranged at one end of the ridge waveguide array and is overlapped with the position of part of the ridge waveguide array; one end of the multimode interference waveguide is closely adjacent to the other end of the ridge waveguide array, and the supersymmetric array waveguide is closely adjacent to the other end of the multimode interference waveguide.

The semiconductor laser takes a surface active Bragg grating as a high-reflection grating and provides single-frequency laser with tunable wavelength for a ridge waveguide array; then, single-frequency and single-mode laser wave gains are amplified by sequentially utilizing the ridge waveguide array, coherent coupling is carried out by utilizing the multimode interference waveguide, secondary transverse mode selection and gain are carried out on the single-frequency light wave by utilizing the super-symmetric array waveguide, the divergence angle of an output laser beam is reduced, and the quality of the device beam is improved, so that the semiconductor laser can provide high-power, narrow-linewidth and wavelength-tunable high-beam-quality laser to the outside.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a semiconductor laser according to an embodiment of the present invention;

FIG. 2 is a right side view of FIG. 1;

FIG. 3 is a front view of FIG. 1;

fig. 4 is a top view of fig. 1.

The waveguide structure comprises a 2-surface active Bragg reflection grating, a 3-ridge waveguide array, a 4-multimode interference waveguide, a 5-super-symmetric array waveguide, a 51-first super-symmetric array waveguide, a 52-second super-symmetric array waveguide, a 6-space modulation structure, a 7-N type substrate layer, an 8-N layer cladding, a 9-N type waveguide layer, a 10-active layer, an 11-P type waveguide layer, a 12-P type cladding and a 13-P type high-doping layer.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In order that those skilled in the art will better understand the disclosure, the invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

Referring to fig. 1 to 4, fig. 1 is a schematic structural diagram of a semiconductor laser according to an embodiment of the present invention; FIG. 2 is a right side view of FIG. 1; FIG. 3 is a front view of FIG. 1; fig. 4 is a top view of fig. 1.

The invention provides a semiconductor laser, which comprises a semiconductor PN junction, and further comprises a surface active Bragg reflection grating 2, a ridge waveguide array 3, a multimode interference waveguide 4 and a super-symmetric array waveguide 5 which are arranged on the semiconductor PN junction.

In the semiconductor laser, the surface active bragg reflection grating 2, the ridge waveguide array 3, the multimode interference waveguide 4 and the super-symmetric array waveguide 5 are distributed along the same row, and in short, if the surface active bragg reflection grating 2, the ridge waveguide array 3, the multimode interference waveguide 4 and the super-symmetric array waveguide 5 are line segments distributed along the respective length directions, the four are located on the same straight line.

In this document, the orientation relationship of each structure in the semiconductor laser will be described by a column direction and a row direction. The array direction is the extension and connection direction of the surface active Bragg reflection grating 2, the ridge waveguide array 3, the multimode interference waveguide 4 and the super-symmetric array waveguide 5, and the row direction is vertical to the array direction. The coordinate system can be referred to the three-dimensional coordinate system established in the drawings of the specification. Wherein the X-axis is equivalent to the column direction and the Y-axis is equivalent to the row direction.

In the semiconductor laser, a surface active Bragg reflection grating 2 is arranged at one end of a ridge waveguide array 3, one end of a multimode interference waveguide 4 is closely adjacent to the other end of the ridge waveguide array 3, and a super-symmetric array waveguide 5 is closely adjacent to the other end of the multimode interference waveguide 4. It can be seen that in the semiconductor laser, the surface active bragg reflection grating 2 is overlapped with the partial ridge waveguide array 3 at the end, and the surface active bragg reflection grating 2 is arranged on the ridge surface of the partial ridge waveguide array 3. The multimode interference waveguide 4 and the super-symmetric array waveguide 5 are adjacent to the other end of the ridge waveguide array 3 in sequence.

The surface active Bragg reflection grating 2 can be etched on the ridge surface of the ridge waveguide array 3 by adopting the technologies of i-line photoetching or plasma etching and the like. Generally, the width of the surface active bragg reflection grating 2 in the row direction is the same as that of the ridge waveguide array 3, and the length of the surface active bragg reflection grating 2 in the column direction depends on the operating parameters of the semiconductor laser. Similarly, the specific geometric parameters of the ridge waveguide array 3, the multimode interference waveguide 4 and the super-symmetric array waveguide 5 can be set according to the working parameters of the semiconductor laser.

Aiming at the semiconductor laser provided by the invention, firstly, a single-frequency laser beam is provided by adopting a surface active Bragg reflection grating 2 arranged on the ridge surface of a ridge waveguide array 3, and the single-frequency laser beam has the characteristics of a single longitudinal mode and a single transverse mode, wherein the characteristic of the single longitudinal mode is beneficial to reducing the line width of the laser; in addition, the surface active bragg reflection grating 2 can also change the magnitude of the injection current, adjust the concentration of the carrier in the surface active bragg reflection grating, further change the effective refractive index of the area where the surface active bragg reflection grating is located, change the bragg wavelength of the surface active bragg reflection grating, and achieve the purpose of tuning the wavelength of the laser. Secondly, the single-frequency laser beam is transmitted to the multi-mode interference waveguide 4 through the ridge waveguide array 3, coherent beam combination is realized by the multi-mode interference waveguide 4, the laser power is improved, and further the output power of the semiconductor laser is improved. Finally, the super-symmetric array waveguide 5 performs transverse mode selection on the coherent combined laser so as to improve the beam quality of the laser output outwards by the semiconductor laser; and coupling the coherent and combined laser to improve the gain, so as to improve the power of the laser output by the semiconductor laser.

The existing laser product obtains high-beam-quality laser output by controlling the transverse mode of light waves, but neglects the problems of longitudinal mode selection and wavelength tuning of the light waves, so that the high-beam-quality laser is multi-longitudinal mode lasing and cannot tune the wavelength, and the requirement of a high-performance laser source of an optical phased array laser radar cannot be met. In comparison, the semiconductor laser provided by the invention can provide high-power laser with tunable wavelength, narrower laser line width and higher beam quality to the outside by utilizing the surface active Bragg reflection grating 2, the ridge waveguide array 3, the multimode interference waveguide 4 and the super-symmetric array waveguide 5, can be applied to equipment such as an optical phased array laser radar and the like, and meets the requirements of the equipment on high-performance laser sources.

The semiconductor laser provided by the present invention will be further described with reference to the accompanying drawings and embodiments.

In addition to the above structure, the semiconductor laser provided by the present invention has a spatial modulation structure 6 in the multi-mode interference waveguide 4, in other words, the spatial modulation structure 6 coincides with the multi-mode interference waveguide 4 in the column direction of the semiconductor laser.

The spatial modulation structure 6 combined with the multi-mode interference waveguide 4 can meet and accurately regulate and control the working parameters of the single-frequency laser beam in coherent beam combination operation. As to the specific configuration of the spatial modulation structure 6, there are included, and not limited to, several cavities arranged within the multimode interference waveguide 4. The cavity can be arranged in the multi-mode interference waveguide 4 by adopting an etching mode, and simply speaking, by removing the local specific position of the good-conductivity layer where the multi-mode interference waveguide 4 is located, the interface resistance of the local specific position is improved, so that ohmic contact cannot be formed at the local specific position. Taking the example that the multi-mode interference waveguide 4 is arranged on the high-doped layer of the semiconductor PN junction, the cavity can be etched at a local specific position of the high-doped layer where the multi-mode interference waveguide 4 is arranged. The cavity can be in the shape of cuboid, cylinder and other special solid geometrical shapes. Referring to fig. 1, in fig. 1, a plurality of rectangular spatial modulation structures 6 are uniformly distributed in a multi-mode interference waveguide 4.

In addition, the spatial modulation structure can also adopt an ion injection mode to improve the interface resistance of the good conductivity layer where the multimode interference waveguide 4 is located at a local specific position, reduce the carrier injection concentration of the local specific position and achieve the purpose of controlling and adjusting the refractive index.

The multimode interference waveguide 4 used in the present invention can be configured as a symmetrical structure or an asymmetrical structure according to the performance requirements of the semiconductor laser for outputting laser light. Taking the specific structure provided in the drawings as an example, the multimode interference waveguide 4 is arranged in a symmetrical structure, and has a plurality of inlet ends for abutting the ridge waveguide array 3 and a plurality of outlet ends for abutting the super-symmetric array waveguide 5.

A plurality of inlet ends of the multimode interference waveguide 4 are respectively connected with a plurality of ridge surfaces of the ridge waveguide array 3, so that all the inlet ends can be uniformly distributed in the row direction of the semiconductor laser, namely the Y-axis direction shown in fig. 1, and similarly, all the ridge surfaces of the ridge waveguide array 3 are uniformly distributed in the row direction of the semiconductor laser.

The super-symmetric arrayed waveguide 5 adopted by the present invention may include a first super-symmetric arrayed waveguide 51 and a second super-symmetric arrayed waveguide. The first and second super-symmetric arrayed waveguides 51 and 52 both extend along the column direction of the semiconductor laser, and are arranged at the same column direction position of the semiconductor laser and adjacent in the row direction of the semiconductor laser. The first super-symmetric array waveguide 51 is used for realizing laser gain, the second super-symmetric array waveguide 52 is used for realizing laser loss, and the first super-symmetric array waveguide and the second super-symmetric array waveguide realize laser coupling together and improve the power of laser.

As for the semiconductor PN junction employed in the present invention, which is also referred to as a device epitaxial wafer, it may include an N-type substrate layer 7, an N-type cladding layer 8, an N-type waveguide layer 9, an active layer 10, a P-type waveguide layer 11, a P-type cladding layer 12, and a P-type highly doped layer 13 laid in layers, and in short, the semiconductor PN junction includes an active layer 10 and P and N layers disposed on both sides of the active layer 10. The semiconductor PN junction is connected to an N-electrode on the N-type substrate layer 7 and to a P-electrode on the P-type highly doped layer 13.

Wherein, the N pole electrode and the P pole electrode can be respectively plated on the outer surface of the N type substrate layer 7 and the outer surface of the P type high doping layer 13. That is, the P-electrode can be regarded as a P-electrode layer, and the N-electrode can be regarded as an N-electrode layer.

The material system of the semiconductor PN junction can be any one of InGaAs, InGaAsP, AlInGaAs and InP. Correspondingly, the semiconductor laser can provide 1300-1600 nm laser to the outside. Of course, the material of the semiconductor PN junction includes and is not limited to the above materials.

Based on the specific structure of the semiconductor PN junction, in the semiconductor laser, the surface active Bragg reflection grating 2, the ridge waveguide array 3, the multimode interference waveguide 4 and the super-symmetric array waveguide 5 are arranged on a P-type cladding and a P-type high doping layer 13. In other words, the surface active bragg reflection grating 2, the ridge waveguide array 3, the multimode interference waveguide 4, and the super-symmetric array waveguide 5 are overlapped with the P-type cladding and the P-type highly doped type of the semiconductor laser in the Z-axis direction shown in fig. 1.

The semiconductor PN junction can be provided by a metal organic compound vapor deposition technique. The surface active Bragg grating 2 is etched to the P-type high-doping layer 13 or only etched to the P-type cladding layer by using an i-line photoetching or plasma etching technology. The ridge waveguide array 3, the multimode interference waveguide 4 and the super-symmetric array waveguide 5 are etched to the P-type high-doped layer 13 by adopting the photoetching or plasma etching technology.

The semiconductor PN junction is in a strip shape; correspondingly, the sum of the array length of the surface active Bragg reflection grating 2, the ridge waveguide array 3, the multimode interference waveguide 4 and the super-symmetric array waveguide 5 can be equal to the length of the semiconductor PN junction. As for the row width of both the ridge waveguide array 3 and the multimode interference waveguide 4, it can be equal to the width of the semiconductor PN junction.

In addition, in the semiconductor laser, a high-reflection film and an anti-reflection film are respectively arranged at two ends of the semiconductor PN junction in the length direction. Wherein, the high reflection film can be arranged at one end close to the surface active Bragg reflection grating 2, and the anti-reflection film can be arranged at one end close to the super-symmetric array waveguide 5.

The semiconductor laser adopting the structure has the advantages of full-surface pattern preparation, simple process and compact structure.

In summary, the semiconductor laser uses the surface active bragg grating as the high reflection grating to provide the single-frequency laser with tunable wavelength; the ridge waveguide array 3 is used for amplifying the gain of single-frequency and single-mode laser waves, and meanwhile, the multimode interference waveguide 4 with a spatial modulation structure 6 is used for carrying out coherent coupling on the laser with tunable wavelength transmitted by the ridge waveguide array 3. And finally, the super-symmetric array waveguide 5 is used for carrying out secondary transverse mode selection and gain on the single-frequency light wave, so that the divergence angle of an output laser beam is reduced, the beam quality of a device is improved, and high-power, narrow-linewidth and wavelength tunable high-beam-quality laser is realized.

The semiconductor laser provided by the present invention is described in detail above. The principles and embodiments of the present invention are explained herein using specific examples, which are presented only to assist in understanding the method and its core concepts. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.