Low-divergence-angle narrow-linewidth high-power semiconductor laser

Abstract

The invention discloses a low-divergence-angle narrow-linewidth high-power semiconductor laser. Relates to the technical field of semiconductor lasers, in particular to a low-divergence-angle narrow-linewidth high-power semiconductor laser. According to the invention, the parabolic waveguide structure is etched in the light field expansion area, and the metal reflector is introduced to realize a novel light field expansion and metal reflector integrated structure, and the transverse divergence angle of a laser mode is reduced through the expansion structure at the tail end of the waveguide. The laser comprises a laser gain area, a light field expansion area and a spectrum purification area at the tail of the light field expansion area. The laser gain region, the light field expansion region and the spectrum purification region at the tail part of the light field expansion region are made of the same laser epitaxial material in the longitudinal direction, the laser gain region is adjacent to the light field expansion region along the horizontal light emitting direction, and the light field expansion region is adjacent to the spectrum purification region at the tail part of the light field expansion region along the horizontal light emitting direction; the longitudinal direction is the direction from the substrate to the contact layer.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor laser, in particular to a low divergence angle narrow linewidth high power semiconductor laser. BACKGROUND

[0002] With the rapid development of high-precision optical measurement, gas detection, laser communication and laser radar, higher requirements are put forward for the spectral purity, coherence and frequency stability of the laser. Semiconductor has the advantages of small size, high electro-optical conversion efficiency, wide wavelength range, fast response speed, high reliability and long service life, and has been widely used in solid laser pumping source, gas detection, laser radar, laser communication and other fields, and has become one of the key devices in the above fields.

[0003] The spectral linewidth of the traditional semiconductor laser is usually in the order of MHz to GHz during the working process due to the limitation of intrinsic frequency noise, spontaneous radiation and carrier fluctuation, which limits its application in high-resolution spectroscopy, interferometry and long-distance coherent communication. Narrow linewidth semiconductor laser has the advantages of small size, light weight, high efficiency, long life, direct current driving, narrow spectral linewidth and good coherence, but has the problems of poor beam quality and large divergence angle. The large divergence angle of narrow linewidth laser will cause the rapid diffusion of laser energy in space, which will seriously limit the transmission efficiency and spatial resolution in long-distance transmission.

[0004] In the prior art, in order to realize spectral linewidth compression, narrow linewidth semiconductor lasers usually integrate frequency selection structures in the resonant cavity or couple with mode selection devices outside the laser cavity, so as to control the gain and loss of different wavelengths; in order to realize the reduction of divergence angle, the external optical system such as spherical lens, cylindrical mirror and microlens array is usually used to shape the light beam. The existing technology can improve the performance of semiconductor laser to some extent, but there are problems such as complex structure difficult to integrate, low coupling efficiency, large power loss, and difficult to optimize divergence angle and linewidth simultaneously. SUMMARY

[0005] In view of the problems of large divergence angle of semiconductor laser and difficult to optimize divergence angle and linewidth simultaneously in the prior art, the purpose of the present application is to provide a low divergence angle narrow linewidth high power semiconductor laser. The present application etches a parabolic waveguide structure in the light field expansion area and introduces a metal mirror to realize a new type of light field expansion and metal mirror integrated structure, and reduces the lateral divergence angle of the laser mode through the expansion structure at the end of the waveguide.

[0006] The laser comprises a laser gain region, a light field expansion region and a spectral purification region at the tail of the light field expansion region. The laser gain region, the optical field extension region, and the spectral purification region at the tail of the optical field extension region are made of the same laser epitaxial material in the longitudinal direction. The laser gain region is adjacent to the optical field extension region along the horizontal light output direction, and the optical field extension region is adjacent to the spectral purification region at the tail of the optical field extension region along the horizontal light output direction. The laser gain region includes: substrate, buffer layer, lower confinement layer, lower waveguide layer, quantum well active region, upper waveguide layer, upper confinement layer, and contact layer; The optical field extension region includes: an optical field extension region substrate, an optical field extension region buffer layer, an optical field extension region lower confinement layer, an optical field extension region waveguide layer, an optical field extension region upper confinement layer, and a metal thin film layer; The spectral purification region at the tail of the optical field extension region includes: a spectral purification region substrate, a spectral purification region buffer layer, a spectral purification region lower confinement layer, a spectral purification region waveguide layer, a spectral purification region upper confinement layer, and an absorbing crystal thin film layer. The longitudinal direction is the direction in which the substrate penetrates to the contact layer.

[0007] Furthermore, the waveguide layer in the optical field extension region includes: a lower waveguide layer in the optical field extension region and an upper waveguide layer in the optical field extension region; The waveguide layer of the spectral clean region includes: a lower waveguide layer and an upper waveguide layer. The materials and thicknesses of the lower waveguide layer in the optical field extension region and the lower waveguide layer in the spectral purification region are the same as those of the lower waveguide layer. The materials of the upper waveguide layer in the optical field extension region and the upper waveguide layer in the spectral purification region are the same as those of the upper waveguide layer.

[0008] Furthermore, the sum of the thicknesses of the waveguide layer in the optical field extension region and the waveguide layer in the spectral purification region is greater than the sum of the thicknesses of the upper waveguide layer and the lower waveguide layer. The difference between the sum of the thicknesses of the waveguide layers in the optical field extension region and the spectral purification region and the sum of the thicknesses of the lower and upper waveguide layers is equal to the thickness of the active region of the quantum well.

[0009] Furthermore, the confinement layer in the light field extension region and the confinement layer in the spectral purification region have the same thickness, ranging from 50 nm to 100 nm.

[0010] Furthermore, the material of the metal thin film layer is an Al thin film, an Au thin film, or an Ag thin film; The material of the absorbing crystal thin film layer is a diamond thin film.

[0011] Furthermore, the laser gain region also includes lateral gratings on both sides of the ridge or DBR gratings on the ridge.

[0012] Furthermore, the substrate, the light field extension region substrate, and the spectral purification region substrate are all made of III-V type semiconductor materials.

[0013] Furthermore, the fabrication method of the low divergence angle, narrow linewidth, high-power semiconductor laser is as follows: S1. On the substrate, the light field extension region substrate and the spectral purification region substrate, the following layers are epitaxially grown sequentially using molecular epitaxy or metal-organic vapor phase epitaxy: buffer layer, light field extension region buffer layer, spectral purification region buffer layer, lower confinement layer, light field extension region lower confinement layer, spectral purification region lower confinement layer, lower waveguide layer, light field extension region lower waveguide layer, spectral purification region lower waveguide layer, quantum well active region, upper waveguide layer, upper confinement layer, contact layer, light field extension region upper waveguide layer, spectral purification region upper waveguide layer, light field extension region upper confinement layer (25) and spectral purification region upper confinement layer to obtain the epitaxial wafer to be prepared. S2. Ridge waveguides, parabolic metal thin film mirrors and Raman effect filter structures are fabricated at the corresponding positions of the laser gain region, the optical field extension region and the spectral purification region at the tail of the optical field extension region in the epitaxial wafer to be prepared, respectively. S3. On the ridge waveguide, fabricate lateral gratings on both sides of the ridge or DBR gratings on the ridge; The preparation scope includes: the upper confinement layer and the contact layer; S4. On the contact layer after step S3, Ti / Pt / Au is sputtered by magnetron sputtering to grow the P-side electrode and obtain the epitaxial wafer to be etched with cleavage grooves. S5. Perform photolithography and etching on the epitaxial wafer to be etched to obtain the cleavage groove, and thin the substrate, the light field extension region substrate and the spectral purification region substrate to 100~120μm; S6. On the back side of the substrate, the light field extension region substrate, and the spectral purification region substrate after step S5, the N-side electrode is grown by magnetron sputtering Ni / AuGe / Au. The S7 and N-side electrodes are rapidly annealed to achieve ohmic contact. Then, according to the cleavage groove, cleavage and sintering are performed to complete the encapsulation and obtain the laser.

[0014] Furthermore, the laser gain region corresponds to the upper confinement layer and the contact layer; The corresponding locations of the optical field extension region are: the waveguide layer on the optical field extension region and the confinement layer on the optical field extension region; The corresponding positions of the spectral cleanup region at the tail of the optical field extension region are: the waveguide layer on the spectral cleanup region and the confinement layer on the spectral cleanup region.

[0015] Furthermore, in step S2, the fabrication of the ridge waveguide includes: etching the ridge structure; Fabrication of a parabolic metal thin-film mirror includes: photolithography of a parabolic pattern and fabrication of a metal thin-film layer using magnetron sputtering technology; The fabrication of the Raman effect filter structure includes: photolithography of the original pattern and fabrication of a microwave absorbing crystal thin film layer using physical vapor deposition or chemical vapor deposition techniques.

[0016] The beneficial effects of the laser described in this invention are as follows: (1) The laser described in this invention forms a parabolic waveguide structure by etching in the optical field extension region and introduces a metal mirror to realize a novel structure integrating optical field extension and metal mirror. The lateral divergence angle of the laser mode is reduced by the extension structure at the end of the waveguide.

[0017] (2) The laser described in this invention is also equipped with a partially reflective metal mirror to optimize the feedback path. At the same time, a Raman-effect absorbing crystal material is introduced at the tail of the light field extension region to construct a precision optical cavity, which purifies the laser into a cleaner and more stable laser. Ultimately, the laser linewidth compression and divergence angle control are optimized in a coordinated manner. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the laser structure described in this invention; 1-Laser gain region, 2-Optical field extension region, 3-Spectral purification region at the tail of the optical field extension region, 11-Substrate, 12-Buffer layer, 13-Lower confinement layer, 14-Lower waveguide layer, 15-Quantum well active region, 16-Upper waveguide layer, 17-Upper confinement layer, 18-Contact layer, 21-Substrate of optical field extension region, 22-Buffer layer of optical field extension region, 23-Lower confinement layer of optical field extension region, 24-Waveguide layer of optical field extension region, 241- 242-Lower waveguide layer of the optical field extension region, 25-Upper waveguide layer of the optical field extension region, 26-Upper confinement layer of the optical field extension region, 31-Substrate of the spectral purification region, 32-Buffer layer of the spectral purification region, 33-Lower confinement layer of the spectral purification region, 34-Waveguide layer of the spectral purification region, 341-Lower waveguide layer of the spectral purification region, 342-Upper waveguide layer of the spectral purification region, 35-Upper confinement layer of the spectral purification region, and 36-Absorbing crystal thin film layer. Detailed Implementation

[0019] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] This embodiment provides a high-power semiconductor laser with low divergence angle and narrow linewidth, using GaSb as a substrate. The structure of the laser is as follows: Figure 1 As shown, the laser includes: a laser gain region 1, a light field extension region 2, and a spectral purification region 3 at the tail of the light field extension region; The laser gain region 1, the optical field extension region 2, and the spectral purification region 3 at the tail of the optical field extension region are made of the same laser epitaxial material in the longitudinal direction. The laser gain region 1 is adjacent to the optical field extension region 2 along the horizontal light output direction, and the optical field extension region 2 is adjacent to the spectral purification region 3 at the tail of the optical field extension region along the horizontal light output direction. The longitudinal direction is the direction in which the substrate 11 extends to the contact layer 18.

[0021] The laser gain region 1, along the horizontal light output direction, includes: contact layer 18; The laser gain region 1 (longitudinal range) includes: substrate 11, buffer layer 12, lower confinement layer 13, lower waveguide layer 14, quantum well active region 15, upper waveguide layer 16, upper confinement layer 17 and contact layer 18; the laser gain region 1 is used to generate optical gain after electrical injection.

[0022] The area corresponding to the horizontal light emission direction of the light field extension region 2 includes: a metal thin film layer 26; the area of ​​the light field extension region 2 (vertical range) includes: a light field extension region substrate 21, a light field extension region buffer layer 22, a light field extension region lower confinement layer 23, a light field extension region waveguide layer 24, a light field extension region upper confinement layer 25, and a metal thin film layer 26. The spectral purification zone 3 at the tail of the light field extension region includes, along the horizontal light output direction, the following range: absorbing crystal thin film layer 36; The spectral purification region 3 (longitudinal range) at the tail of the optical field extension region includes: a spectral purification region substrate 31, a spectral purification region buffer layer 32, a spectral purification region lower confinement layer 33, a spectral purification region waveguide layer 34, a spectral purification region upper confinement layer 35, and an absorbing crystal thin film layer 36.

[0023] Substrate 11, optical field extension region substrate 21, and spectral purification region substrate 31 are different parts of the same semiconductor laser substrate. The substrate materials are all III-V semiconductor materials, and GaSb is used in this embodiment.

[0024] The materials and thicknesses of the buffer layer 12, the light field extension region buffer layer 22, and the spectral purification region buffer layer 32 are all the same, and those skilled in the art can set them according to actual needs.

[0025] The materials and thicknesses of the lower confinement layer 13, the lower confinement layer 23 of the light field extension region, and the lower confinement layer 33 of the spectral purification region are all the same, and those skilled in the art can set them according to actual needs.

[0026] The optical field extension region waveguide layer 24 includes: a lower optical field extension region waveguide layer 241 and an upper optical field extension region waveguide layer 242; The spectral clean region waveguide layer 34 includes: a lower spectral clean region waveguide layer 341 and an upper spectral clean region waveguide layer 342; The materials and thicknesses of the lower waveguide layer 241 in the optical field extension region and the lower waveguide layer 341 in the spectral purification region are the same as those of the lower waveguide layer 14. Those skilled in the art can set them according to actual needs. The materials of the upper waveguide layer 242 in the optical field extension region and the upper waveguide layer 342 in the spectral purification region are the same as those of the upper waveguide layer 16. Those skilled in the art can set them according to actual needs. The sum of the thicknesses of the waveguide layer 24 in the optical field extension region and the waveguide layer 34 in the spectral purification region is greater than the sum of the thicknesses of the upper waveguide layer 16 and the lower waveguide layer 14. Those skilled in the art can set this according to actual needs. The difference between the sum of the thicknesses of the optical field extension region waveguide layer 24 and the spectral purification region waveguide layer 34 and the sum of the thicknesses of the lower waveguide layer 14 and the upper waveguide layer 16 is equal to the thickness of the quantum well active region 15. Those skilled in the art can set this according to actual needs.

[0027] The waveguide layer 242 in the aforementioned optical field extension region, after undergoing parabolic pattern photolithography, forms a parabolic waveguide that can guide photons to a specific propagation path (parabolic waveguide), effectively limiting the lateral diffusion of photons, concentrating more energy in the laser output region, making the beam more concentrated in the longitudinal direction, reducing the far-field divergence angle of the laser beam, effectively enhancing the output power and beam quality of the laser, and achieving an increase in the output laser power of the laser.

[0028] The upper confinement layer 17, the upper confinement layer 25 of the light field extension region, and the upper confinement layer 35 of the spectral purification region are made of the same material; The upper confinement layer 25 in the light field extension region and the upper confinement layer 35 in the spectral purification region have the same thickness, ranging from 50nm to 100nm. In this embodiment, both are 80nm.

[0029] The contact layer 18, the metal thin film layer 26, and the absorbing crystal thin film layer 36 have the same thickness, which can be set by those skilled in the art according to actual needs.

[0030] The metal thin film layer 26 is made of Al, Au, or Ag thin film. The metal thin film layer 26 constitutes the metal reflector of the light field extension region 2, achieving a high reflectivity of over 90% and reducing photon leakage. This invention introduces a metal reflector into the light field extension region 2, realizing a novel structure integrating light field extension and a metal reflector. Through the extension structure at the waveguide end (i.e., the parabolic waveguide of the waveguide layer 242 in the light field extension region, reducing the lateral divergence angle of the laser mode), and in conjunction with the (reflective) metal reflector, the feedback path is optimized. The material of the absorbing crystal thin film layer 36 is a diamond thin film. The spectral purification region 3 at the tail of the optical field extension region uses the diamond thin film to form a Raman effect absorbing crystal material to construct a precision optical cavity (Raman scattering filter). That is, the diamond thin film has the ability to dissipate vibrations very quickly. When the laser photons interact with the phonons in the absorbing crystal thin film, the photon energy is converted into phonon vibrations. At the same time, scattered light is generated to form a Raman effect, thereby converting the phase noise of the laser into random motion of phonons, reducing the fluctuation of the laser frequency, significantly reducing residual noise, purifying the laser, and further compressing the laser linewidth.

[0031] The present invention also uses electron beam lithography to prepare lateral gratings on both sides of the ridge waveguide in the laser gain region 1, or prepares DBR gratings on the ridge waveguide to compress the laser linewidth (the preparation range is: upper confinement layer 17 and contact layer 18).

[0032] Example 2 This embodiment further defines Embodiment 1, and provides a method for fabricating a low-divergence-angle, narrow-linewidth, high-power semiconductor laser: Step 1: On substrate 11, light field extension region substrate 21, and spectral purification region substrate 31, a buffer layer 12, a light field extension region buffer layer 22, a spectral purification region buffer layer 32, a lower confinement layer 13, a lower confinement layer 23 in the light field extension region, a lower confinement layer 33 in the spectral purification region, a lower waveguide layer 14, a lower waveguide layer 241 in the light field extension region, and a lower waveguide layer 341 in the spectral purification region are grown using molecular beam epitaxy to obtain the first-stage epitaxial wafer; Step 2: Deposit a SiO2 dielectric layer on the surface of the epitaxial wafer in the first stage to obtain the epitaxial wafer in the second stage; Step 3: Using photolithography, a patterned substrate is prepared on the epitaxial wafer of the second stage. Ultraviolet lithography is performed using positive photoresist. A window is opened at the corresponding position of the laser gain region 1 (lower waveguide layer 14) to etch and remove the SiO2 dielectric layer, resulting in the epitaxial wafer of the third stage. At this time, the dielectric layer on the lower waveguide layer 14 is etched away, while the dielectric layers at the corresponding positions of the optical field extension region 2 (lower waveguide layer 241 of the optical field extension region) and the corresponding positions of the spectral purification region 3 at the tail of the optical field extension region (lower waveguide layer 341 of the spectral purification region) are retained. Step 4: Using molecular beam epitaxy, the remaining portion of the laser gain region 1 is epitaxially grown on the epitaxial wafer of the third stage, including: quantum well active region 15, upper waveguide layer 16, upper confinement layer 17 and contact layer 18, to obtain the epitaxial wafer of the fourth stage. Step 5: Remove the dielectric layer on the surface of the epitaxial wafer at the corresponding position of the optical field extension region 2 (waveguide layer 241 below the optical field extension region) and the corresponding position of the spectral purification region 3 at the tail of the optical field extension region (waveguide layer 341 below the spectral purification region) to obtain the epitaxial wafer at the fifth stage. In this embodiment, a selective etching solution that has no corrosive effect on the epitaxial material but has a corrosive effect on the dielectric layer material is used. In this embodiment, dilute HF acid is selected to etch the SiO2 dielectric layer material. Step 6: Deposit a SiO2 dielectric layer on the surface of the fifth-stage epitaxial wafer using PECVD technology to obtain the sixth-stage epitaxial wafer; Step 7: Use photolithography to fabricate the patterned substrate of the epitaxial wafer in the sixth stage. Use positive photoresist for ultraviolet lithography to open windows and etch away the dielectric layer at the corresponding positions of the light field extension region 2 (lower waveguide layer 241 of the light field extension region) and the corresponding positions of the spectral purification region 3 at the tail of the light field extension region (lower waveguide layer 341 of the spectral purification region), to obtain the epitaxial wafer in the seventh stage. At this time, the dielectric layer on the corresponding position of the laser gain region 1 (contact layer 18) is retained. Step 8: Using molecular beam epitaxy, on the epitaxial wafer of the seventh stage, sequentially grow the upper waveguide layer material of the light field extension region 2 and the spectral purification region 3 at the tail of the light field extension region (i.e., the upper waveguide layer 242 of the light field extension region and the upper waveguide layer 342 of the spectral purification region, the thickness of the upper waveguide layer 242 of the light field extension region and the upper waveguide layer 342 of the spectral purification region are the sum of the thicknesses of the quantum well active region 5 and the upper waveguide layer 16), as well as the upper confinement layer 25 of the light field extension region and the upper confinement layer 35 of the spectral purification region, to obtain the epitaxial wafer of the eighth stage. The material and thickness of the upper confinement layer 25 of the light field extension region and the upper confinement layer 35 of the spectral purification region are the same as those of the upper confinement layer 17. Step 9: Remove the dielectric layer on the surface of the eighth-stage epitaxial wafer to obtain the ninth-stage epitaxial wafer. In this embodiment, a selective etching solution that has no corrosive effect on the epitaxial material but has a corrosive effect on the dielectric layer material is used. In this embodiment, dilute HF acid is selected to etch the SiO2 dielectric layer material. Step 10: Using ultraviolet lithography, ridge structures, parabolic waveguide structures, and spectral purification region structures are fabricated on the epitaxial wafer of the ninth stage, respectively, at corresponding positions in the laser gain region 1, the epitaxial optical field extension region 2, and the spectral purification region 3 at the tail of the optical field extension region. This yields a ridge waveguide, a parabolic metal thin-film mirror, and a Raman effect filter structure. The specific fabrication process is as follows: The ridge structure (ridge waveguide) is etched on the upper confinement layer 17 and the contact layer 18 using wet or dry etching methods, and then the photoresist is removed. like Figure 1As shown, parabolic patterns of the light field extension region 2 are formed on the confinement layer 25 and the waveguide layer 242 of the light field extension region using ultraviolet lithography. Then, a metal thin film layer 26 is prepared on the etched confinement layer 25 of the light field extension region as a metal mirror using magnetron sputtering. Finally, the photoresist is removed, and the lift-off process is completed to obtain the parabolic metal thin film mirror. like Figure 1 As shown, the original pattern of the spectral purification region 3 at the tail of the optical field extension region is lithographically formed on the confinement layer 35 and the waveguide layer 342 of the spectral purification region using ultraviolet lithography. The absorbing crystal thin film layer 36 is prepared on the etched confinement layer 35 of the spectral purification region using physical vapor deposition or chemical vapor deposition technology with diamond thin film as a filter structure. Then the photoresist is removed and the lift-off process is completed to obtain the Raman effect filter structure. Step 11: Fabricate lateral gratings on both sides of the ridge waveguide or fabricate DBR gratings on the ridge waveguide using electron beam lithography, and remove the photoresist; The fabrication area includes: the upper confinement layer 17 and the contact layer 18; Step 12: Using PECVD technology, SiO2 dielectric layers are deposited on the surfaces of the ridge waveguide (after processing in Step 11), the parabolic metal thin film mirror, and the Raman effect filter structure to obtain the tenth-stage epitaxial wafer; Step 12: Using ultraviolet lithography, a laser electrode windowing process is carried out on the laser gain region 1 (contact layer 18) in the tenth-stage epitaxial wafer (using magnetron sputtering to sputter P-side Ti / Pt / Au electrodes, then immersing in acetone solution and ultrasonically removing the photoresist to complete the metal electrode lift-off process), the P-side electrode pattern is lithographically formed, the P-side electrode growth is completed, and the eleventh-stage epitaxial wafer is obtained; Step 13: Perform cleavage trench photolithography and etching on the eleventh-stage epitaxial wafer to prepare cleavage trenches and obtain cleavage trench patterns parallel to the cleavage surface. This helps to clearly mark the chip cutting point, resulting in the twelfth-stage epitaxial wafer.

[0033] Step 17: The (N-type GaSb) substrate 11, the light field extension region substrate 21, and the spectral purification region substrate 31 of the twelfth-stage epitaxial wafer are thinned (to 100~120μm) using thinning and polishing equipment to obtain the thirteenth-stage epitaxial wafer. The above thinning can reduce the series resistance and improve the heat dissipation capacity. The substrate is mechanically thinned to 100μm using a 9μm aluminum oxide aqueous solution, and then polished to a bright surface on a polishing cloth with a chemical polishing solution. Step 18: Using a magnetron sputtering device, Ni / AuGe / Au thin films are deposited on the back side of the substrate 11, the light field extension region substrate 21, and the spectral purification region substrate 31 of the thirteenth-stage epitaxial wafer to complete the N-side electrode fabrication; Step 19: Rapid thermal annealing of the N-side electrode to form an ohmic contact. The temperature is rapidly raised to 335°C in a nitrogen atmosphere, held for 120 seconds, and then rapidly cooled to room temperature. After completing the rapid thermal annealing process, a 100nm thick Au film is sputtered. Step 20: According to the cleaving groove, cleave the Bar strip and perform cavity film evaporation. The antireflection film has a reflectivity of less than 5% and the antireflection film has a reflectivity of greater than 95%. Then, cleave the single tube to obtain a single tube core. Step 21: Rapidly alloy the laser chip and ceramic sheet onto the heat sink in an alloy furnace, and bring out the positive and negative electrodes through Au wires and copper strips to obtain the laser described in this invention.

[0034] The above description is only a preferred embodiment of the present invention. It should be noted that the scope of protection of the present invention is not limited thereto. For those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A low-divergence-angle, narrow-linewidth, high-power semiconductor laser, characterized in that, The laser includes: a laser gain region (1), a light field extension region (2), and a spectral purification region (3) at the tail of the light field extension region. The laser gain region (1), the optical field extension region (2), and the spectral purification region (3) at the tail of the optical field extension region are made of the same laser epitaxial material in the longitudinal direction. The laser gain region (1) is adjacent to the optical field extension region (2) along the horizontal light output direction, and the optical field extension region (2) is adjacent to the spectral purification region (3) at the tail of the optical field extension region along the horizontal light output direction. The laser gain region (1) includes: a substrate (11), a buffer layer (12), a lower confinement layer (13), a lower waveguide layer (14), a quantum well active region (15), an upper waveguide layer (16), an upper confinement layer (17), and a contact layer (18). The light field extension region (2) includes: a light field extension region substrate (21), a light field extension region buffer layer (22), a light field extension region lower confinement layer (23), a light field extension region waveguide layer (24), a light field extension region upper confinement layer (25), and a metal thin film layer (26). The spectral purification region (3) at the tail of the optical field extension region includes: a spectral purification region substrate (31), a spectral purification region buffer layer (32), a spectral purification region lower confinement layer (33), a spectral purification region waveguide layer (34), a spectral purification region upper confinement layer (35), and an absorbing crystal thin film layer (36). The longitudinal direction is the direction in which the substrate (11) extends through the contact layer (18).

2. The low divergence angle, narrow linewidth, high-power semiconductor laser according to claim 1, characterized in that, The waveguide layer (24) in the optical field extension region includes: the lower waveguide layer (241) in the optical field extension region and the upper waveguide layer (242) in the optical field extension region. The waveguide layer (34) of the spectral clean region includes: the lower waveguide layer (341) of the spectral clean region and the upper waveguide layer (342) of the spectral clean region. The materials and thicknesses of the lower waveguide layer (241) in the optical field extension region and the lower waveguide layer (341) in the spectral purification region are the same as those of the lower waveguide layer (14); The materials of the upper waveguide layer (242) in the optical field extension region and the upper waveguide layer (342) in the spectral purification region are the same as those of the upper waveguide layer (16).

3. A low divergence angle, narrow linewidth, high-power semiconductor laser according to claim 2, characterized in that, The sum of the thicknesses of the waveguide layer (24) in the optical field extension region and the waveguide layer (34) in the spectral purification region is greater than the sum of the thicknesses of the upper waveguide layer (16) and the lower waveguide layer (14). The difference between the sum of the thicknesses of the optical field extension region waveguide layer (24) and the spectral purification region waveguide layer (34) and the sum of the thicknesses of the lower waveguide layer (14) and the upper waveguide layer (16) is equal to the thickness of the quantum well active region (15).

4. A low divergence angle, narrow linewidth, high-power semiconductor laser according to claim 3, characterized in that, The upper confinement layer (25) in the light field extension region and the upper confinement layer (35) in the spectral purification region have the same thickness, ranging from 50 nm to 100 nm.

5. A low divergence angle, narrow linewidth, high-power semiconductor laser according to claim 4, characterized in that, The material of the metal thin film layer (26) is an Al thin film, an Au thin film, or an Ag thin film; The material of the absorbing crystal thin film layer (36) is a diamond thin film.

6. A low divergence angle, narrow linewidth, high-power semiconductor laser according to claim 5, characterized in that, The laser gain region (1) also includes lateral gratings on both sides of the ridge or DBR gratings on the ridge.

7. A low divergence angle, narrow linewidth, high-power semiconductor laser according to claim 6, characterized in that, The substrate (11), the light field extension region substrate (21), and the spectral purification region substrate (31) are all made of III-V type semiconductor materials.

8. A low divergence angle, narrow linewidth, high-power semiconductor laser according to claim 7, characterized in that, The fabrication method of the low divergence angle, narrow linewidth, high-power semiconductor laser is as follows: S1. On the substrate (11), the light field extension region substrate (21), and the spectral purification region substrate (31), the following layers are epitaxially grown sequentially using molecular epitaxy or metal-organic vapor phase epitaxy: buffer layer (12), light field extension region buffer layer (22), spectral purification region buffer layer (32), lower confinement layer (13), light field extension region lower confinement layer (23), spectral purification region lower confinement layer (33), lower waveguide layer (14), light field extension region lower waveguide layer (241), spectral purification region lower waveguide layer (341), quantum well active region (15), upper waveguide layer (16), upper confinement layer (17), contact layer (18), light field extension region upper waveguide layer (242), spectral purification region upper waveguide layer (342), light field extension region upper confinement layer (25), and spectral purification region upper confinement layer (35) to obtain the epitaxial wafer to be prepared. S2. Ridge waveguides, parabolic metal thin film mirrors and Raman effect filter structures are fabricated at the corresponding positions of the laser gain region (1), the optical field extension region (2) and the spectral purification region (3) at the tail of the optical field extension region in the epitaxial wafer to be prepared. S3. On the ridge waveguide, fabricate lateral gratings on both sides of the ridge or DBR gratings on the ridge; The preparation scope includes: the upper confinement layer (17) and the contact layer (18); S4. On the contact layer (18) after step S3, Ti / Pt / Au is sputtered by magnetron sputtering to grow the P-side electrode and obtain the epitaxial wafer to be etched with cleavage grooves. S5. Photolithography and etching are performed on the epitaxial wafer to be etched to obtain the cleavage groove, and the substrate (11), the light field extension region substrate (21) and the spectral purification region substrate (31) are thinned to 100~120μm; S6. On the back side of the substrate (11), the light field extension region substrate (21), and the spectral purification region substrate (31) after step S5, the N-side electrode is grown by magnetron sputtering Ni / AuGe / Au. The S7 and N-side electrodes are rapidly annealed to achieve ohmic contact. Then, according to the cleavage groove, cleavage and sintering are performed to complete the encapsulation and obtain the laser.

9. A low divergence angle, narrow linewidth, high-power semiconductor laser according to claim 8, characterized in that, The laser gain region (1) corresponds to the upper confinement layer (17) and the contact layer (18). The corresponding positions of the optical field extension region (2) are: the upper waveguide layer (242) and the upper confinement layer (25) of the optical field extension region. The corresponding positions of the spectral purification region (3) at the tail of the optical field extension region are: the waveguide layer (342) on the spectral purification region and the confinement layer (35) on the spectral purification region.

10. A low-divergence-angle, narrow-linewidth, high-power semiconductor laser according to claim 9, characterized in that, In step S2, fabricating the ridge waveguide includes: etching the ridge structure; The preparation of a parabolic metal thin film mirror includes: parabolic pattern photolithography and preparation of a metal thin film layer by magnetron sputtering (26). The fabrication of the Raman effect filter structure includes: photolithography of the original pattern and fabrication of a microwave absorbing crystal thin film layer using physical vapor deposition or chemical vapor deposition techniques (36).

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