High-power narrow-linewidth semiconductor laser

Abstract

The invention relates to the technical field of laser, in particular to a high-power narrow-linewidth semiconductor laser which is sequentially and coaxially provided with a semiconductor laser unit, a fast axis collimating lens, a slow axis collimating lens, a half-wave plate, a polarization splitting prism and a volume Bragg grating in the light path direction. The semiconductor laser unit emits linearly polarized light beams; the fast axis collimating mirror and the slow axis collimating mirror are respectively used for collimating and compressing two divergence angles of the linearly polarized light beam; the half-wave plate is used for adjusting the linear polarization degree of the linearly polarized light beam in free operation; the polarization splitting prism is used for realizing polarization separation of linearly polarized light beams; the volume Bragg grating is used for narrowing the spectral line width of the linearly polarized light beam in free operation; while external cavity feedback is realized, the temperature rise problem of high laser energy absorbed by the volume Bragg grating is effectively solved, and the problem of central wavelength drift of the laser after line width narrowing is inhibited; and a better spectrum locking effect can be obtained by regulating and controlling the feedback power of the outer cavity.

Description

Technical Field

[0001] The present invention belongs to the field of laser technology, and particularly relates to a high-power narrow-linewidth semiconductor laser. Background Art

[0002] The external cavity feedback technology based on volume Bragg grating (VBG) has been proven to be one of the most effective technical methods for realizing narrow linewidth and spectral locking of free-running high-power semiconductor lasers. This technology can significantly reduce the spectral linewidth of semiconductor lasers, narrowing it from the nanometer level to the sub-nanometer level. Therefore, it expands the application range of semiconductor lasers, enabling semiconductor lasers to be used for efficient pumping of alkali metal vapor lasers, metastable rare gas lasers, and disk lasers, and playing an important role in many fields such as laser processing, laser medicine, and national defense security.

[0003] The traditional external cavity feedback structure combines a high-power semiconductor laser and a volume Bragg grating (VBG) with low diffraction efficiency. Usually, the structure includes three parts, namely a semiconductor laser light source, a beam shaping system, and a low-diffraction-efficiency VBG. However, as the power of the laser light source increases, the laser power irradiated on the VBG also increases accordingly. The VBG has an inherent temperature drift characteristic. When irradiated by high-power laser, the VBG absorbs light energy and generates a temperature rise, which causes a drift of the diffraction center wavelength, further leading to the instability of the laser center wavelength after spectral locking. Especially in order to obtain high-power laser output, when combining multiple semiconductor lasers for combined beam output, it is easy to produce a broadening effect of the spectral linewidth, thus having a significant impact on the pumping efficiency.

[0004] The disadvantages of semiconductor lasers in the prior art are mainly reflected in two aspects: On the one hand, it is the problem of the drift of the laser center wavelength after linewidth narrowing. Due to the temperature drift characteristic of the VBG, when high-power laser is incident on the VBG, the diffraction center wavelength will produce a red shift phenomenon due to the heat absorption of the material. Therefore, the laser spectrum after spectral locking will still drift towards the long wavelength band. In order to obtain high-power laser output, when multiple semiconductor laser units are introduced into the structure, even if the VBG corresponds to each unit laser for external cavity feedback one by one, the temperature drift characteristic of the VBG will cause a certain deviation in the center wavelength of each laser beam after spectral locking. Therefore, the combined beam spectrum will produce a broadening effect of the linewidth.

[0005] On the other hand, there is the problem that the external cavity feedback power cannot be regulated. In the external cavity feedback structure, when the parameters of the semiconductor laser chip are determined, the diffraction efficiency of the VBG is the most crucial parameter. Theoretically, the higher the diffraction efficiency of the VBG, the easier it is to suppress the free spectral range of the laser, thereby obtaining a better linewidth narrowing effect. This is because when the incident power of the laser is determined, the VBG with a high diffraction efficiency can reflect the diffracted wavelength laser with a higher power into the inner cavity of the chip for mode competition, suppressing the output of the laser with other wavelengths. However, if the diffraction efficiency of the VBG is too high, it is easy to cause optical catastrophic damage (COD) on the front cavity surface of the chip, resulting in the failure of the laser chip. Therefore, the traditional structure usually selects a VBG with a low diffraction efficiency for external cavity feedback to prevent chip failure. After the diffraction efficiency of the VBG is reduced, the laser power reflected back into the inner cavity of the chip decreases accordingly, and it is easy to have a situation where the free spectral range is difficult to suppress, affecting the spectral narrowing effect. This also reflects the compatibility problem between the laser power and the diffraction efficiency of the VBG. Since the diffraction efficiency of the VBG is a fixed value when the incident laser power is determined in the traditional structure, once the diffraction efficiency of the VBG is determined, the laser power returned to the inner cavity of the chip after external cavity feedback is also a fixed value and cannot be tuned. When performing spectral locking of multiple laser units, if the diffraction efficiency of the selected VBG does not match the corresponding laser chip, it will affect the spectral locking effect. Usually, it is necessary to replace the VBG and then perform the locking experiment, and a large number of VBGs need to be screened to find the parameters that match the laser chip, which greatly increases the engineering difficulty. Summary of the Invention

[0006] In view of this, the present invention aims to provide a new structure for polarization separation beam control of external cavity feedback, specifically providing a high-power narrow-linewidth semiconductor laser with external cavity feedback power control, effectively solving the problems of central wavelength drift and uncontrollable external cavity feedback power of high-power narrow-linewidth semiconductor lasers.

[0007] To achieve the above object, the technical solution of the present invention is realized as follows: A high-power narrow-linewidth semiconductor laser, specifically a high-power narrow-linewidth semiconductor laser with external cavity feedback power control, the high-power narrow-linewidth semiconductor laser is coaxially provided with a semiconductor laser unit, a fast-axis collimating mirror, a slow-axis collimating mirror, a half-wave plate, a polarization beam splitter prism, and a volume Bragg grating in the optical path direction in sequence; The semiconductor laser unit emits a linearly polarized light beam, the linearly polarized light beam includes a semiconductor laser fast-axis beam and a semiconductor laser slow-axis beam, the semiconductor laser fast-axis beam has a semiconductor laser fast-axis divergence angle, and the semiconductor laser slow-axis beam has a semiconductor laser slow-axis divergence angle; The fast-axis collimating mirror is used to collimate and compress the semiconductor laser fast-axis divergence angle, and the slow-axis collimating mirror is used to collimate and compress the semiconductor laser slow-axis divergence angle; The half-wave plate is used to adjust the linear polarization degree of the linearly polarized light beam in free running; the polarization beam splitter prism is used to realize the polarization separation of the linearly polarized light beam; the volume Bragg grating is used to narrow the spectral linewidth of the linearly polarized light beam in free running.

[0008] Furthermore, the semiconductor laser unit has a single-tube laser structure. When the semiconductor laser unit runs freely, the central laser wavelength is 780 nm ± 3 nm, and the spectral linewidth is 5 nm.

[0009] Furthermore, the linearly polarized light beam includes P-polarized light and S-polarized light. The polarization degree of the P-polarized light is 95%, and the polarization degree of the S-polarized light is 5%.

[0010] Furthermore, the polarization beam splitter prism is used to enable the P-polarized light to pass through and, at the same time, reflect the S-polarized light.

[0011] Furthermore, the fast-axis divergence angle of the semiconductor laser is the divergence angle in the vertical direction, and the angular range of the fast-axis divergence angle of the semiconductor laser is 30° to 60°; the slow-axis divergence angle of the semiconductor laser is the divergence angle in the horizontal direction, and the angular range of the slow-axis divergence angle of the semiconductor laser is 8° to 12°.

[0012] Furthermore, the focal length of the fast-axis collimating mirror is 0.3 mm, and the focal length of the slow-axis collimating mirror is 14 mm.

[0013] Furthermore, the central wavelength of the half-wave plate is 780 nm ± 5 nm.

[0014] Furthermore, the central wavelength of the polarization beam splitter prism is 780 nm ± 10 nm.

[0015] Furthermore, the diffraction central wavelength of the volume Bragg grating is 780 nm ± 0.1 nm, and the diffraction efficiency of the volume Bragg grating is 95% ± 3%.

[0016] Furthermore, the thickness of the volume Bragg grating is 3 mm.

[0017] Compared with the prior art, the present invention can achieve the following beneficial effects: The present invention proposes a new structure for polarization separation beam control with external cavity feedback, specifically provides a high-power narrow-linewidth semiconductor laser with external cavity feedback power control, and solves the problems of central wavelength drift and non-adjustable external cavity feedback power of high-power narrow-linewidth semiconductor lasers.

[0018] The high-power narrow-linewidth semiconductor laser with external cavity feedback power control provided by the present invention utilizes the characteristics of linearly polarized semiconductor laser light, combines semiconductor laser polarization splitting technology and volume Bragg grating (VBG) external cavity feedback technology. A single laser beam is divided into two beams by a polarization beam splitter prism. Among them, the low-power laser is incident on a VBG with high diffraction efficiency for external cavity feedback spectral locking. Since the incident power is low, the heat absorption effect of the VBG is greatly reduced, and the stability of the central wavelength is significantly improved.

[0019] In addition, for the high-power narrow-linewidth semiconductor laser with external cavity feedback power control provided by the present invention, a half-wave plate (HWP) is added between the laser and the polarization beam splitter prism. By adjusting the angle of the HWP, the linear polarization degree of the initial semiconductor laser beam can be changed. After passing through the polarization beam splitter prism, the laser power incident on the VBG can be continuously changed, realizing the tuning of the external cavity feedback power. Therefore, the screening difficulty of the VBG and the engineering difficulty are greatly reduced. Since the angle of the HWP can be tuned in real time, a better spectral locking effect can be obtained. Description of the Drawings

[0020] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 It is a schematic diagram of the optical path structure of the high-power narrow-linewidth semiconductor laser according to the embodiment of the present invention.

[0021] Description of the reference numerals in the drawings: 1. Semiconductor laser unit; 2. Fast-axis collimating mirror; 3. Slow-axis collimating mirror; 4. Half-wave plate; 5. Polarization beam splitter prism; 6. Volume Bragg grating. Detailed Embodiments

[0022] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation to the present invention.

[0023] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0024] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality of" is two or more than two.

[0025] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "mounted", "connected", "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific circumstances.

[0026] The specific embodiment of the present invention provides a high-power narrow-linewidth semiconductor laser, specifically providing a high-power narrow-linewidth semiconductor laser with external cavity feedback power control. The high-power narrow-linewidth semiconductor laser is coaxially provided with a semiconductor laser unit, a fast-axis collimating mirror, a slow-axis collimating mirror, a half-wave plate, a polarization beam splitter prism, and a volume Bragg grating in sequence along the optical path direction; the semiconductor laser unit emits a linearly polarized light beam, the linearly polarized light beam includes a semiconductor laser fast-axis beam and a semiconductor laser slow-axis beam, the semiconductor laser fast-axis beam has a semiconductor laser fast-axis divergence angle, and the semiconductor laser slow-axis beam has a semiconductor laser slow-axis divergence angle; the fast-axis collimating mirror is used to collimate and compress the semiconductor laser fast-axis divergence angle, and the slow-axis collimating mirror is used to collimate and compress the semiconductor laser slow-axis divergence angle; the half-wave plate is used to adjust the linear polarization degree of the freely operating linearly polarized light beam; the polarization beam splitter prism is used to achieve the polarization separation of the linearly polarized light beam; the volume Bragg grating is used to narrow the spectral linewidth of the freely operating linearly polarized light beam.

[0027] The high-power narrow-linewidth semiconductor laser provided by the specific embodiment of the present invention changes the linear polarization degree of the initial incident laser by rotating the angle between the half-wave plate and the incident laser. In this way, after passing through the polarization beam splitter prism, the laser power incident on the volume Bragg grating can be changed, and thus a better linewidth narrowing effect can be obtained. It is necessary to creatively combine and use a half-wave plate + polarization beam splitter prism + volume Bragg grating with high diffraction efficiency to obtain an ideal linewidth narrowing effect.

[0028] In a specific embodiment, the high-power narrow-linewidth semiconductor laser provided has no limitation on the wavelength and can theoretically be any wavelength, such as 450 nm, 808 nm, 976 nm, etc. The corresponding lenses and VBG should correspond to the corresponding wavelength bands. As an example, the central wavelength of the laser when the semiconductor laser unit operates freely is 780 nm ± 3 nm, and the spectral linewidth is 5 nm. The linearly polarized light beam includes P-polarized light and S-polarized light. The polarization degree of the P-polarized light is 95%, and the polarization degree of the S-polarized light is 5%. The polarization beam splitter prism is used to transmit the P-polarized light and reflect the S-polarized light at the same time. The fast-axis divergence angle of the semiconductor laser is the divergence angle in the vertical direction, and the angle range of the fast-axis divergence angle of the semiconductor laser is 30° to 60°. The slow-axis divergence angle of the semiconductor laser is the divergence angle in the horizontal direction, and the angle range of the slow-axis divergence angle of the semiconductor laser is 8° to 12°. The focal length of the fast-axis collimating lens is 0.3 mm, and the focal length of the slow-axis collimating lens is 14 mm. The central wavelength of the half-wave plate is 780 nm ± 5 nm. The central wavelength of the polarization beam splitter prism is 780 nm ± 10 nm. The diffraction central wavelength of the volume Bragg grating is 780 nm ± 0.1 nm, and the diffraction efficiency of the volume Bragg grating is 95% ± 3%. The thickness of the volume Bragg grating is 3 mm.

[0029] In the technical solution provided by the specific embodiment of the present invention, a volume Bragg grating with high diffraction efficiency is used, and the diffraction efficiency is 95% ± 3%. At present, most of the reported ones use volume Bragg gratings with low diffraction efficiency, and the diffraction efficiency is usually 15% ± 3%. By using a volume Bragg grating with high diffraction efficiency, the present invention can better realize the narrow linewidth effect by low-power laser incident on the volume Bragg grating, and effectively solve the problem of temperature rise caused by the volume Bragg grating absorbing high laser energy, and suppress the problem of the central wavelength drift of the laser after linewidth narrowing. Moreover, the technical solution of the present application further combines the characteristics of linearly polarized light of the semiconductor laser. By introducing a half-wave plate and changing the angle of the half-wave plate, the laser power incident on the volume Bragg grating can be controlled, so as to obtain a better spectral locking effect by regulating the external cavity feedback power.

[0030] The present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0031] As Figure 1 shown, it is a schematic diagram of the optical path structure of a high-power narrow-linewidth semiconductor laser provided by an embodiment of the present invention. It can be seen from the figure that the high-power narrow-linewidth semiconductor laser with external cavity feedback power control provided by this embodiment is coaxially provided with a semiconductor laser unit 1, a fast-axis collimating mirror 2, a slow-axis collimating mirror 3, a half-wave plate 4, a polarization beam splitter prism 5, and a volume Bragg grating 6 in sequence along the optical path direction; among them, the semiconductor laser unit 1 emits a linearly polarized light beam. The semiconductor laser unit 1 is a single-tube laser structure. The laser center wavelength of the semiconductor laser unit 1 during free running is 780 nm ± 3 nm, and the spectral linewidth is 5 nm; the emitted linearly polarized light beam includes P-polarized light and S-polarized light. The polarization degree of the P-polarized light is 95%, and the polarization degree of the S-polarized light is 5%.

[0032] In a specific embodiment, the linearly polarized light beam includes a semiconductor laser fast-axis beam and a semiconductor laser slow-axis beam. The semiconductor laser fast-axis beam has a semiconductor laser fast-axis divergence angle, and the semiconductor laser slow-axis beam has a semiconductor laser slow-axis divergence angle; among them, the semiconductor laser fast-axis divergence angle is the divergence angle in the vertical direction, and the angle range of the semiconductor laser fast-axis divergence angle before collimation is 30° to 60°; the semiconductor laser slow-axis divergence angle is the divergence angle in the horizontal direction, and the angle range of the semiconductor laser slow-axis divergence angle before collimation is 8° to 12°; the light field in the fast-axis direction is a fundamental-mode Gaussian distribution. Although the divergence angle is large, the stripe width is small, and the beam quality is good and close to the diffraction limit; the light field in the slow-axis direction is a Hermite-Gaussian distribution. The divergence angle is smaller than that in the fast-axis direction, but the stripe width is larger, and the beam quality is very poor; in the technical solution provided by the embodiment of the present invention, the fast-axis collimating mirror (FAC) 2 is used to collimate and compress the semiconductor laser fast-axis divergence angle, and the slow-axis collimating mirror (SAC) 3 is used to collimate and compress the semiconductor laser slow-axis divergence angle; after collimation, the laser divergence angles in both directions can reach the order of 10 mrad; specifically, the focal length of the fast-axis collimating mirror 2 is 0.3 mm, and the focal length of the slow-axis collimating mirror 3 is 14 mm.

[0033] In a specific embodiment, the linearly polarized light beam collimated and compressed by the fast-axis collimator 2 and the slow-axis collimator 3 is adjusted for its linear polarization degree by a half-wave plate (HWP) 4. Specifically, the spectrum can be observed by a spectrometer, and the angle of the half-wave plate is rotated. When a better spectral narrowing effect is obtained, the half-wave plate is at the optimal position at this time; the central wavelength of the half-wave plate 4 is 780 nm ± 5 nm; then the polarization splitting of the linearly polarized light beam is realized by a polarization beam splitter prism 5; the linearly polarized light beam includes P-polarized light and S-polarized light. The central wavelength of the polarization beam splitter prism 5 is 780 nm ± 10 nm. The polarization beam splitter prism 5 can transmit the P-polarized light and, at the same time, reflect the S-polarized light; by adjusting the angle of the half-wave plate 4, the tuning of the power of the linearly polarized light beam incident on the volume Bragg grating (VBG) 6 can be realized; the volume Bragg grating 6 is used to narrow the spectral linewidth of the free-running linearly polarized light beam; specifically, the diffraction central wavelength of the volume Bragg grating is 780 nm ± 0.1 nm, the diffraction efficiency is 95% ± 3%, and the thickness is 3 mm. By using a VBG with a high diffraction efficiency to match the low-power laser incidence, the low-power laser is incident on the VBG for external cavity feedback, and the laser power incident on the VBG can be adjusted. Therefore, the drift of the central wavelength after spectral locking can be suppressed, and the free spectral output of the laser can be suppressed, so as to obtain a better spectral locking effect.

[0034] A specific embodiment of the present invention provides a high-power narrow-linewidth semiconductor laser with external cavity feedback power control, which solves the problems of central wavelength drift and uncontrollable external cavity feedback power of high-power narrow-linewidth semiconductor lasers.

[0035] The high-power narrow-linewidth semiconductor laser with external cavity feedback power control provided by the present invention utilizes the characteristics of semiconductor laser linearly polarized light, combines semiconductor laser polarization splitting technology and volume Bragg grating (VBG) external cavity feedback technology, and divides a single laser beam into two beams by a polarization beam splitter prism. Among them, the low-power laser is incident on a VBG with a high diffraction efficiency for external cavity feedback spectral locking. Since the incident power is low, the heat absorption effect of the VBG is greatly reduced, and the central wavelength stability is significantly improved.

[0036] In addition, for the high-power narrow-linewidth semiconductor laser with external cavity feedback power control provided by the present invention, by adding a half-wave plate (HWP) between the laser and the polarization beam splitter prism, the linear polarization degree of the initial semiconductor laser beam can be changed by adjusting the angle of the HWP. After passing through the polarization beam splitter prism, the laser power incident on the VBG can be continuously changed, realizing the tuning of the external cavity feedback power. Therefore, the screening difficulty of the VBG and the engineering difficulty are greatly reduced. Since the angle of the HWP can be tuned in real time, a better spectral locking effect can be obtained.

[0037] It should be understood that the various forms of processes shown above can be used, with steps reordered, added or deleted. For example, the steps described in the disclosure of the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and no limitation is imposed herein.

[0038] The above specific embodiments do not constitute a limitation on the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub - combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A high-power narrow-linewidth semiconductor laser, characterized in that: The high-power narrow-linewidth semiconductor laser is coaxially arranged in sequence along the optical path direction with a semiconductor laser unit, a fast-axis collimator, a slow-axis collimator, a half-wave plate, a polarization beam splitter prism and a volume Bragg grating; The semiconductor laser unit emits a linearly polarized light beam, the linearly polarized light beam includes a semiconductor laser fast axis beam and a semiconductor laser slow axis beam, the semiconductor laser fast axis beam has a semiconductor laser fast axis divergence angle, and the semiconductor laser slow axis beam has a semiconductor laser slow axis divergence angle; The fast axis collimator is used to collimate and compress the fast axis divergence angle of the semiconductor laser, and the slow axis collimator is used to collimate and compress the slow axis divergence angle of the semiconductor laser; The half-wave plate is used to adjust the linear polarization degree of the free-running linearly polarized light beam; the polarization beam splitter is used to achieve polarization separation of the linearly polarized light beam; and the volume Bragg grating is used to narrow the spectral line width of the free-running linearly polarized light beam.

2. The high-power narrow-linewidth semiconductor laser according to claim 1, characterized in that: The semiconductor laser unit is a single-tube laser structure. When the semiconductor laser unit is in free operation, the laser center wavelength is 780nm±3nm, and the spectrum line width is 5nm.

3. The high-power narrow-linewidth semiconductor laser according to claim 1, characterized in that: The linearly polarized light beam includes P polarized light and S polarized light, the polarization degree of the P polarized light is 95%, and the polarization degree of the S polarized light is 5%.

4. The high-power narrow-linewidth semiconductor laser according to claim 3, characterized in that: The polarization beam splitter prism is used to achieve the transmission of the P polarized light and, at the same time, the reflection of the S polarized light.

5. The high-power narrow-linewidth semiconductor laser according to claim 1, characterized in that: The semiconductor laser fast axis divergence angle is a divergence angle in the vertical direction, and the angle range of the semiconductor laser fast axis divergence angle is 30° to 60°; the semiconductor laser slow axis divergence angle is a divergence angle in the horizontal direction, and the angle range of the semiconductor laser slow axis divergence angle is 8° to 12°.

6. The high-power narrow-linewidth semiconductor laser according to claim 1, characterized in that: The focal length of the fast axis collimator is 0.3 mm, and the focal length of the slow axis collimator is 14 mm.

7. The high-power narrow-linewidth semiconductor laser according to claim 1, characterized in that: The central wavelength of the half-wave plate is 780nm±5nm.

8. The high-power narrow-linewidth semiconductor laser according to claim 1, characterized in that: The central wavelength of the polarization beam splitter is 780nm±10nm.

9. The high-power narrow-linewidth semiconductor laser according to claim 1, characterized in that: The diffraction center wavelength of the volume Bragg grating is 780nm±0.1nm, and the diffraction efficiency of the volume Bragg grating is 95%±3%.

10. The high-power narrow-linewidth semiconductor laser according to claim 1, characterized in that: The thickness of the volume Bragg grating is 3 mm.

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