Spectral beam combining device of semiconductor laser

Abstract

The invention discloses a spectrum beam combining device of a semiconductor laser. The spectrum beam combining device comprises a fast axis collimating mirror, a slow axis collimating mirror, a first rotatable half-wave plate, a first cylindrical surface transmission lens and a first diffraction grating which are sequentially arranged along the optical axis of the semiconductor laser, a second cylindrical transmission lens, a second rotatable half-wave plate, a third cylindrical transmission lens and a second diffraction grating are sequentially arranged in the 0-level transmission light beam direction of the first diffraction grating, and a total reflection mirror is arranged in the-1-level diffraction direction of the second diffraction grating, so that the-1-level diffraction light beam returns to the semiconductor laser as a feedback light beam after being reflected; and-1-level diffracted light of the first diffraction grating is used as output light. The second rotatable half-wave plate and the second diffraction grating are introduced into the outer cavity, effective utilization of 0-level transmission light is achieved, accurate adjustment of the proportion of the output light beam and the feedback light beam is achieved through the first rotatable half-wave plate, and therefore wavelength locking is achieved, and meanwhile combined light beam output with the highest power and efficiency is obtained.

Description

Technical Field

[0001] This invention relates to the field of semiconductor laser technology, and more specifically to a spectral beam combining device for semiconductor lasers. Background Technology

[0002] High-power semiconductor lasers (HPDLs) can be used not only as pump sources for solid-state lasers (such as wafer, fiber, and slab lasers), but also directly for laser irradiation and material processing (such as surface treatment, welding, additive manufacturing, and cutting). The improvement in output power and brightness is the main driving force for the expansion of the application range of high-power semiconductor lasers.

[0003] Spectral beam combining technology for high-power semiconductor lasers is an effective method to achieve high power and high brightness output. Its basic principle is similar to wavelength division multiplexing (WDM) in communications. Different laser units in a semiconductor laser are locked to different wavelengths. Through the dispersion effect of dispersive elements, the output beams of each unit overlap in space and are emitted in the same direction, thus achieving beam combining. After beam combining, the overall beam quality is close to that of a single unit, and the power is the sum of the powers of each unit.

[0004] External cavity spectral beam combining is one of the main methods for achieving spectral beam combining. It uses a partially reflecting external cavity mirror to reflect a portion of the -1st order diffraction beam from the diffraction grating back to the array as feedback light to achieve wavelength locking. The remaining portion of the -1st order diffraction beam is then used for spectral beam combining and output. During beam combining, the 0th order transmitted light from the diffraction grating is wasted as useless light. This is especially true when the polarization degree of the semiconductor laser array is low, where the proportion of the 0th order transmitted light from the diffraction grating is even higher, significantly affecting the optical-to-optical conversion efficiency of the external cavity spectral beam combining device. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a spectral beam combining device for semiconductor lasers. By introducing a rotatable half-wave plate and a second diffraction grating into the external cavity, it achieves efficient utilization of the 0th-order transmitted light and enables precise adjustment of the ratio of the output beam to the feedback beam.

[0006] This invention discloses a spectral beam combining device for a semiconductor laser, comprising: a semiconductor laser and a fast-axis collimating mirror, a slow-axis collimating mirror, a first rotatable half-wave plate, a first cylindrical transmission lens, and a first diffraction grating arranged sequentially along the optical axis of the semiconductor laser;

[0007] The first diffraction grating has a second cylindrical transmission lens, a second rotatable half-wave plate, a third cylindrical transmission lens, and a second diffraction grating arranged sequentially in the 0th order transmission beam direction. A total reflection mirror is arranged in the -1st order diffraction direction of the second diffraction grating. The -1st order diffracted beam of the second diffraction grating is reflected by the total reflection mirror as a feedback beam back to the semiconductor laser. The -1st order diffracted light of the first diffraction grating is used as the output light. The first rotatable half-wave plate and the second rotatable half-wave plate can adjust the rotation angle of the wave plate.

[0008] As a further improvement of the present invention, the first cylindrical transmission lens, the second cylindrical transmission lens, and the third cylindrical transmission lens have the same focal length f; the semiconductor laser is disposed on the focal plane of the first cylindrical transmission lens, the first diffraction grating is disposed on the focal plane of the first cylindrical transmission lens and the second cylindrical transmission lens, the distance between the second cylindrical transmission lens and the third cylindrical transmission lens is 2f, and the second diffraction grating is disposed on the focal plane of the third cylindrical transmission lens; the total reflection mirror performs total reflection on the -1st order diffracted beam incident on it and feeds it back to the semiconductor laser to form external cavity wavelength locking.

[0009] As a further improvement of the present invention, the first rotatable half-wave plate and the second rotatable half-wave plate can change the polarization state of the light beam passing through the half-wave plate by rotating the angle of the half-wave plate; by rotating the first rotatable half-wave plate, the polarization state of the output light beam of the semiconductor laser can be changed, thereby changing the splitting ratio of the transmitted light and the diffracted light of the first diffraction grating to adjust the ratio of the feedback beam and the output beam; by rotating the second rotatable half-wave plate, the polarization state of the 0th order transmitted beam of the first diffraction grating can be changed to match the polarization state of the second diffraction grating, thereby obtaining the highest diffraction efficiency and thus obtaining the highest feedback light power.

[0010] As a further improvement of the present invention, the semiconductor laser includes a semiconductor laser array or multiple single-tube semiconductor lasers, and the front cavity surface of the semiconductor laser is coated with an anti-reflection film with a transmittance ≥99%.

[0011] As a further improvement of the present invention, the fast-axis collimating lens is a cylindrical microlens, and the slow-axis collimating lens is a cylindrical microlens array; the light-transmitting surfaces of both the fast-axis and slow-axis collimating lenses are coated with anti-reflection films with a transmittance ≥99%.

[0012] As a further improvement of the present invention, the light-transmitting surfaces of the first cylindrical transmission lens, the second cylindrical transmission lens, and the third cylindrical transmission lens are all coated with anti-reflection films, with a transmittance ≥99%; the first cylindrical transmission lens and the second cylindrical transmission lens constitute a 4f telephoto telescope system; the first cylindrical transmission lens superimposes the light beams emitted by each light-emitting unit of the semiconductor laser onto the first diffraction grating; the third cylindrical transmission lens superimposes the 0th order transmitted light beam of the first diffraction grating onto the second diffraction grating; the second cylindrical transmission lens superimposes the feedback light beam onto the first diffraction grating.

[0013] As a further improvement of the present invention, both the light-transmitting surfaces of the first rotatable half-wave plate and the second rotatable half-wave plate are coated with an anti-reflection film with a transmittance of ≥99%.

[0014] As a further improvement of the present invention, the first diffraction grating and the second diffraction grating are placed at the Littrow angle with the optical axis of the output beam of the semiconductor laser.

[0015] As a further improvement of the present invention, the total reflection mirror is coated with a high-reflectivity film with a reflectivity >99%.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] The spectral beam combining device of this invention separates the feedback beam and the output beam optical paths, using the 0th order transmitted beam of the first diffraction grating as the feedback beam, thus achieving effective utilization of the 0th order transmitted beam. Since the ratio of 0th order transmitted light to -1st order diffracted light differs when beams of different polarization states are incident on the first diffraction grating, this invention can precisely adjust the ratio of feedback beam to output beam by changing the rotation angle of the first rotatable half-wave plate, thereby changing the polarization state of the semiconductor laser output beam. The polarization state of the 0th order transmitted beam is changed by the second rotatable half-wave plate to match the polarization mode of the second diffraction grating. Thus, wavelength locking is achieved while obtaining the highest power and efficiency combined beam output. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Therefore, they should not be regarded as a limitation of the scope. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a front view of the spectral beam combining device for a semiconductor laser array according to Embodiment 1 of the present invention;

[0020] Figure 2 This is a top view of the spectral beam combining device for a semiconductor laser array according to Embodiment 1 of the present invention;

[0021] Figure 3 This is a schematic diagram showing the polarization state change of the output beam of the semiconductor laser array of the present invention as it passes through the first rotatable half-wave plate and the first diffraction grating.

[0022] Figure 4 This is a schematic diagram of the spectral beam combining device for a multi-single-tube semiconductor laser according to Embodiment 2 of the present invention.

[0023] In the picture:

[0024] 1. Semiconductor laser array; 2. Fast-axis collimating lens; 3. Slow-axis collimating lens; 4. First rotatable half-wave plate; 5. First cylindrical transmission lens; 6. First diffraction grating; 7. Second cylindrical transmission lens; 8. Second rotatable half-wave plate; 9. Third cylindrical transmission lens; 10. Second diffraction grating; 11. Total reflection mirror; 12. Multiple single-tube semiconductor lasers. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. 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.

[0026] The present invention will now be described in further detail with reference to the accompanying drawings:

[0027] Example 1

[0028] like Figure 1 As shown, the present invention provides a spectral beam combining device for a semiconductor laser array, specifically comprising: a semiconductor laser array 1, a fast-axis collimating lens 2, a slow-axis collimating lens 3, a first rotatable half-wave plate 4, a first cylindrical transmission lens 5, a first diffraction grating 6, a second cylindrical transmission lens 7, a second rotatable half-wave plate 8, a third cylindrical transmission lens 9, a second diffraction grating 10, and a total reflection mirror 11; the fast-axis collimating lens 2, the slow-axis collimating lens 3, the first rotatable half-wave plate 4, the first cylindrical transmission lens 5, the first diffraction grating 6, the second cylindrical transmission lens 7, the second rotatable half-wave plate 8, the third cylindrical transmission lens 9, and the second diffraction grating 10 are sequentially placed along the optical axis of the output beam of the semiconductor laser array 1; the total reflection mirror 11 is placed in the -1st order diffraction path of the second diffraction grating 10 and is perpendicular to the optical axis of the -1st order diffraction beam.

[0029] In this embodiment, the slow axis of the semiconductor laser array 1 is horizontal, and the fast axis is perpendicular to the horizontal. Its front cavity surface is coated with an anti-reflection film with a transmittance ≥99%, and its polarization state is TE. The light-transmitting surfaces of the fast-axis collimating lens 2 and the slow-axis collimating lens 3 are coated with anti-reflection films with a transmittance ≥99%, used to collimate the laser emitted from the semiconductor laser array 1, reduce the beam divergence angle, and allow the beam to be incident approximately parallel onto the first rotatable half-wave plate 4. The light-transmitting surface of the first rotatable half-wave plate 4 is also coated with an anti-reflection film with a transmittance ≥99%, used to change the polarization state of the output beam from the semiconductor laser array 1. The beam passes through the first rotatable half-wave plate 4 and is incident onto the first cylindrical transmission lens 5.

[0030] The first cylindrical transmission lens 5, the second cylindrical transmission lens 7, and the third cylindrical transmission lens 9 have the same focal length, and their light-transmitting surfaces are coated with an anti-reflection film, achieving a transmittance ≥99%. The distance between the first cylindrical transmission lens 5 and the semiconductor laser array 1 and the first diffraction grating 6 is the same as the lens focal length. It converts the output beams of each light-emitting unit of the semiconductor laser array 1 into different angles along the slow axis and superimposes them onto the first diffraction grating 6. The polarization mode of the first diffraction grating 6 is TM mode, and it is placed at a Littrow angle with the optical axis to obtain the highest diffraction efficiency of the grating. The -1st order diffracted beam of the first diffraction grating 6 is the output beam.

[0031] In the slow axis direction of the semiconductor laser array 1, the light beam incident on the first diffraction grating 6 is diffracted, and the 0th order transmitted light is incident on the second cylindrical transmission lens 7 at different angles. The distance between the second cylindrical transmission lens 7 and the first diffraction grating 6 is the focal length of the lens. The beam passing through the second cylindrical transmission lens 7 becomes an approximately parallel beam and is incident on the second rotatable half-wave plate 8. The light-transmitting surface of the second rotatable half-wave plate 8 is coated with an anti-reflection film with a transmittance of ≥99%, which is used to change the polarization state of the incident beam to match the polarization mode of the second diffraction grating 10. The beam passes through the second rotatable half-wave plate 8 and is incident on the third cylindrical transmission lens 9. The distance between the third cylindrical transmission lens 9 and the second cylindrical transmission lens 7 is twice the focal length. The beam passes through the third cylindrical transmission lens 9 and is converted into different angles along the slow axis direction and superimposed onto the second diffraction grating 10. The polarization mode of the second diffraction grating 10 is the TM mode, which is placed at a Littrow angle with the optical axis to obtain the highest diffraction efficiency of the grating. The -1st order diffracted beam of the second diffraction grating 10 is reflected by the total reflection mirror 11 and returns along the original path to the semiconductor laser array 1 as feedback light for wavelength locking.

[0032] Figure 3This diagram illustrates the polarization state change of the output beam from the semiconductor laser array of the present invention as it passes through the first rotatable half-wave plate 4 and the first diffraction grating 6. The splitting ratio of the diffraction grating is related to the proportion of the TE and TM modes of the incident beam polarization state. The polarization mode of the first diffraction grating 6 is TM. When the TE mode component of the incident beam polarization state is more abundant, the proportion of the 0th-order transmitted beam is larger; when the TM mode component of the incident beam polarization state is more abundant, the proportion of the -1st-order transmitted beam is larger. Therefore, the polarization state of the output beam from the semiconductor laser array 1 can be adjusted by adjusting the angle of the first rotatable half-wave plate 4, thereby changing the proportion of the 0th-order transmitted light and the -1st-order diffracted light of the first diffraction grating 6. Simultaneously, by adjusting the angle of the second rotatable half-wave plate 8, the polarization state of the 0th-order transmitted light of the first diffraction grating 6 is matched with the polarization mode of the second diffraction grating 10, achieving the highest diffraction efficiency. Furthermore, the polarization state of the beam passing back and forth through the half-wave plate remains unchanged, thus achieving the highest feedback optical power. By adjusting the angle of the first rotatable half-wave plate 4, the ratio of the feedback beam to the output beam can be precisely controlled, achieving wavelength locking while obtaining the highest power and efficiency of the combined beam output.

[0033] Example 2

[0034] like Figure 4As shown, the present invention provides a spectral beam combining device for multiple single-tube semiconductor lasers. The difference from Embodiment 1 is that the semiconductor laser array 1 is replaced with multiple single-tube semiconductor lasers 12. Specifically, it includes: multiple single-tube semiconductor lasers 12, a fast-axis collimating lens 2, a slow-axis collimating lens 3, a first rotatable half-wave plate 4, a first cylindrical transmission lens 5, a first diffraction grating 6, a second cylindrical transmission lens 7, a second rotatable half-wave plate 8, a third cylindrical transmission lens 9, a second diffraction grating 10, and a total reflection mirror 11. The fast-axis collimating lens 2, the slow-axis collimating lens 3, the first rotatable half-wave plate 4, the first cylindrical transmission lens 5, the first diffraction grating 6, the second cylindrical transmission lens 7, the second rotatable half-wave plate 8, the third cylindrical transmission lens 9, and the second diffraction grating 10 are placed sequentially along the optical axis of the output beam of the multiple single-tube semiconductor laser 12. The total reflection mirror 11 is placed in the -1st order diffraction path of the second diffraction grating 10 and is perpendicular to the optical axis of the -1st order diffraction beam. The front cavity surface of the multi-single-tube semiconductor laser 12 is coated with an anti-reflection film, with a transmittance ≥99%. The light-transmitting surfaces of the first cylindrical transmission lens 5, the second cylindrical transmission lens 7, and the third cylindrical transmission lens 9 are all coated with anti-reflection films, with a transmittance ≥99%. The light-transmitting surfaces of the first rotatable half-wave plate 4 and the second rotatable half-wave plate 8 are also coated with anti-reflection films, with a transmittance ≥99%. The total reflection mirror 11 is coated with a high-reflection film, with a reflectance >99%. The first cylindrical transmission lens 5, the second cylindrical transmission lens 7, and the third cylindrical transmission lens 9 have the same focal length. The first diffraction grating 6 and the second diffraction grating 10 are placed at a Littrow angle to the optical axis. The multi-single-tube semiconductor laser 12 is placed at the focal plane of the first cylindrical transmission lens 5. The first diffraction grating 6 is placed at the focal plane of the first cylindrical transmission lens 5 and the second cylindrical transmission lens 7. The distance between the second cylindrical transmission lens 7 and the third cylindrical transmission lens 9 is twice the focal length. The second diffraction grating 10 is placed at the focal plane of the third cylindrical transmission lens 9. The -1st order diffracted beam from the second diffraction grating 10 is reflected by the total reflection mirror 11 and returns along its original path to the multi-single-tube semiconductor laser 12 as feedback light for wavelength locking. The -1st order diffracted beam from the first diffraction grating 6 is the output beam. By adjusting the angle of the first rotatable half-wave plate 4, the ratio of the feedback beam to the output beam can be precisely controlled, achieving wavelength locking while obtaining the highest power and efficiency combined beam output.

[0035] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A spectral beam combining apparatus for a semiconductor laser, comprising: include: A semiconductor laser and a fast-axis collimating lens, a slow-axis collimating lens, a first rotatable half-wave plate, a first cylindrical transmission lens, and a first diffraction grating arranged sequentially along the optical axis of the semiconductor laser; The first diffraction grating has a second cylindrical transmission lens, a second rotatable half-wave plate, a third cylindrical transmission lens, and a second diffraction grating arranged sequentially in the 0th order transmission beam direction. A total reflection mirror is arranged in the -1st order diffraction direction of the second diffraction grating. The -1st order diffracted beam of the second diffraction grating is reflected by the total reflection mirror as a feedback beam back to the semiconductor laser. The -1st order diffracted light of the first diffraction grating is used as the output light. The first rotatable half-wave plate and the second rotatable half-wave plate can adjust the rotation angle of the wave plate.

2. The apparatus according to claim 1, wherein the semiconductor laser is a distributed feedback laser. The first cylindrical transmission lens, the second cylindrical transmission lens, and the third cylindrical transmission lens have the same focal length f; the semiconductor laser is disposed on the focal plane of the first cylindrical transmission lens, the first diffraction grating is disposed on the focal plane of the first cylindrical transmission lens and the second cylindrical transmission lens, the distance between the second cylindrical transmission lens and the third cylindrical transmission lens is 2f, and the second diffraction grating is disposed on the focal plane of the third cylindrical transmission lens; the total reflection mirror performs total reflection on the -1st order diffracted beam incident on it and feeds it back to the semiconductor laser to form external cavity wavelength locking.

3. The apparatus according to claim 1, wherein the semiconductor laser is a distributed feedback laser. The first and second rotatable half-wave plates can change the polarization state of the light beam passing through them by rotating the angle of the half-wave plates. By rotating the first rotatable half-wave plate, the polarization state of the output beam of the semiconductor laser can be changed, thereby changing the splitting ratio of the transmitted light and diffracted light of the first diffraction grating to adjust the ratio of the feedback beam and the output beam. By rotating the second rotatable half-wave plate, the polarization state of the 0th order transmitted beam of the first diffraction grating can be changed to match the polarization state of the second diffraction grating, thereby obtaining the highest diffraction efficiency and thus the highest feedback light power.

4. The spectral beam combining device for a semiconductor laser as described in any one of claims 1 to 3, characterized in that, The semiconductor laser includes a semiconductor laser array or multiple single-tube semiconductor lasers, and the front cavity surface of the semiconductor laser is coated with an anti-reflection film with a transmittance of ≥99%.

5. The spectral beam combining device for a semiconductor laser as described in any one of claims 1 to 3, characterized in that, The fast-axis collimating lens is a cylindrical microlens, and the slow-axis collimating lens is an array of cylindrical microlenses; both the fast-axis and slow-axis collimating lenses have anti-reflection coatings on their light-transmitting surfaces, with a transmittance ≥99%.

6. The spectral beam combining device for a semiconductor laser as described in any one of claims 1 to 3, characterized in that, The light-transmitting surfaces of the first, second, and third cylindrical transmission lenses are all coated with anti-reflection films, with a transmittance ≥99%. The first and second cylindrical transmission lenses form a 4f telephoto telescope system. The first cylindrical transmission lens superimposes the light beams emitted by each light-emitting unit of the semiconductor laser onto the first diffraction grating. The third cylindrical transmission lens superimposes the 0th order transmitted light beam from the first diffraction grating onto the second diffraction grating. The second cylindrical transmission lens superimposes the feedback light beam onto the first diffraction grating.

7. The spectral beam combining device for a semiconductor laser as described in any one of claims 1 to 3, characterized in that, Both the first and second rotatable half-wave plates have anti-reflection coatings on their light-transmitting surfaces, with a transmittance ≥99%.

8. The spectral beam combining device for a semiconductor laser as described in any one of claims 1 to 3, characterized in that, The first and second diffraction gratings are positioned at the Littrow angle relative to the optical axis of the semiconductor laser output beam.

9. The spectral beam combining device for a semiconductor laser as described in any one of claims 1 to 3, characterized in that, The total reflection mirror is coated with a high-reflectivity film with a reflectivity >99%.

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