A spectral beam combining device for a linear array semiconductor laser

Abstract

This invention discloses a spectral beam combining device for a linear array semiconductor laser, comprising: a fast-axis collimating lens, a slow-axis collimating lens, a first cylindrical transmission lens, and a diffraction grating arranged sequentially along the optical axis of the linear array semiconductor laser; a second cylindrical transmission lens and a first concave mirror group arranged sequentially in the direction of the 0th order diffraction beam of the diffraction grating, and a second concave mirror group arranged in the direction of the 1st order diffraction beam, with the -1st order diffracted light of the diffraction grating serving as the output light; the first and second concave mirror groups adjusting their angles according to the "smile" effect of the linear array semiconductor laser, so that the feedback light returns to the corresponding light-emitting unit of the linear array semiconductor laser to form effective feedback; simultaneously, the curved surface of the first concave mirror group along the fast axis direction of the linear array semiconductor laser converges the diverging beam in the fast axis direction, so that the beam is fed back to the original light-emitting unit, improving the feedback efficiency and enabling the light-emitting unit to achieve stable wavelength locking.

Description

Technical Field

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

[0002] Semiconductor lasers have many advantages such as high efficiency, small size, long life, rich wavelengths and direct electric drive. However, due to limitations in beam quality and the output power of a single emitting unit, they are usually only used as pump sources for other lasers and in applications where beam quality requirements are not high.

[0003] Beam combining technology is a common method for obtaining high-power semiconductor lasers. It is generally divided into two main categories: coherent beam combining and incoherent beam combining. Coherent beam combining utilizes the coherence of laser light to increase the brightness of the output beam by controlling the phase relationship of each emitting unit to generate constructive interference. Although coherent beam combining can effectively improve the beam quality of semiconductor laser arrays, this method requires high adjustment precision and is easily affected by external environmental interference, making it difficult to obtain stable high-power laser output. Spectral beam combining, a type of incoherent beam combining, avoids these drawbacks and is relatively easy to implement, making it an effective method for improving the beam quality and brightness of semiconductor laser arrays.

[0004] Spectral beam combining technology utilizes dispersive elements to simultaneously spatially overlap multiple laser beams of different wavelengths in the near and far fields, combining them into a single-aperture output laser. The overall beam quality after combining is close to that of a single emitting unit, while the output power is N times that of a single emitting unit. Spectral beam combining technology has two structures: open-loop (without an output coupling mirror) and closed-loop (with an output coupling mirror). The main difference between the two lies in the locking method of the wavelengths of each emitting unit. Compared to the closed-loop spectral beam combining structure, the open-loop structure uses the 0th-order diffraction beam of the grating to achieve feedback locking of the emitting unit, avoiding the dumping and waste of the 0th-order diffraction beam. This effectively solves the problems of power loss and low beam combining efficiency in the feedback cavity of the -1st-order diffraction beam used in the closed-loop structure.

[0005] While open-loop spectral beam combining structures can effectively reduce power loss, the low 0th-order diffraction efficiency of the grating leads to a significant "smile" effect in the semiconductor array. This results in insufficient simultaneous feedback beams from each emitting unit due to positional deviations in the feedback beams, causing problems such as wavelength locking only in some units, poor output beam quality, and in severe cases, even failure to achieve spectral beam combining. The "smile" effect is an inherent and unavoidable problem in semiconductor array packaging, severely limiting the application of open-loop spectral beam combining structures. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a spectral beam combining device for linear array semiconductor lasers. By utilizing the angle adjustment and converging effect of the separated concave mirrors, it can achieve effective external cavity feedback and stable wavelength locking of the open-loop spectral beam combining structure. This overcomes the adverse effects of the "simle" effect on wavelength locking in open-loop spectral beam combining, providing a new solution for achieving stable open-loop spectral beam combining in conventional commercial semiconductor laser arrays.

[0007] This invention discloses a spectral beam combining device for a linear array semiconductor laser, comprising: a linear array semiconductor laser and, along the optical axis of the linear array semiconductor laser, a fast-axis collimating lens, a slow-axis collimating lens, a first cylindrical transmission lens, and a diffraction grating arranged sequentially; a second cylindrical transmission lens and a first concave mirror group are arranged sequentially in the direction of the 0th order diffraction beam of the diffraction grating, and a second concave mirror group is arranged in the direction of the 1st order diffraction beam, wherein the -1st order diffracted light of the diffraction grating is used as the output light; wherein the angles of the first concave mirror group and the second concave mirror group are adjustable.

[0008] As a further improvement of the present invention, the linear array semiconductor laser and the diffraction grating are disposed on the focal plane of the first cylindrical transmission lens, and the first concave mirror group and the diffraction grating are disposed on the focal plane of the second cylindrical transmission lens.

[0009] As a further improvement of the present invention, the light-transmitting surfaces of the first cylindrical transmission lens and the second cylindrical transmission lens are both coated with anti-reflection films, with a transmittance ≥99%; the focal length f of the first cylindrical transmission lens and the second cylindrical transmission lens is the same, forming a 4f telephoto telescope system; the first cylindrical transmission lens superimposes the light beams emitted by each light-emitting unit on the linear array semiconductor laser onto the diffraction grating, and the second cylindrical transmission lens superimposes the feedback light beams onto the diffraction grating.

[0010] As a further improvement of the present invention, the first concave mirror group and the second concave mirror group are coated with a high-reflectivity film with a reflectivity >99%; the first concave mirror group and the second concave mirror group are respectively placed in the direction of the 0th order diffraction beam and the direction of the 1st order diffraction beam perpendicular to the grating, so as to reflect the diffraction beam incident on them and feed it back to the linear array semiconductor laser to form external cavity wavelength locking.

[0011] As a further improvement of the present invention, both the first concave mirror group and the second concave mirror group include two separate concave mirrors. The two separate concave mirrors are obtained by separating a single concave mirror from the center along the fast axis of the linear array semiconductor laser and placing them close together. The two separate concave mirrors adjust their angles according to the "smile" effect of the linear array semiconductor laser so that the feedback light returns to the corresponding light-emitting unit of the linear array semiconductor laser to form effective feedback.

[0012] As a further improvement of the present invention, the curved surface of the first concave reflector group is along the fast axis direction of the linear array semiconductor laser, which converges the diverging beam in the fast axis direction, so that the beam is fed back to the original light-emitting unit, thereby improving the feedback efficiency and enabling the light-emitting unit to achieve stable wavelength locking.

[0013] As a further improvement of the present invention, the front cavity surface of the linear array semiconductor laser is coated with an antireflection film with a transmittance of ≥99% to reduce the influence of internal cavity feedback and better achieve external cavity wavelength locking.

[0014] 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%; the fast-axis and slow-axis collimating lenses collimate the fast and slow axes of the laser output from the linear array semiconductor laser, respectively, thereby reducing the beam divergence angle.

[0015] As a further improvement of the present invention, the diffraction grating is placed at the Littrow angle with the optical axis or the placement angle of the diffraction grating satisfies that the light beam is incident at a Littrow angle, so as to obtain the highest diffraction efficiency.

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

[0017] 1. The concave reflector proposed in this invention has a converging effect on the fast axis of the feedback beam by the curved surface along the fast axis, so that more beams return to the original light-emitting unit to form effective feedback, thereby making the wavelength locking of the light-emitting unit more stable and realizing stable spectral beam combining.

[0018] 2. The concave reflector assembly of the present invention can adjust the angle according to the deviation of the light-emitting unit in the fast axis direction and the optical axis direction caused by the "smile" effect, so that the center beam of the light-emitting unit with positional deviation is perpendicularly incident on the concave reflector and returns to the original light-emitting unit to form effective feedback, thereby achieving precise wavelength locking. Attached Figure Description

[0019] 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.

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

[0021] Figure 2 This is a top view of the spectral beam combining device of the linear array semiconductor laser according to Embodiment 1 of the present invention;

[0022] Figure 3 This is a schematic diagram of the first concave mirror group or the second concave mirror group in Embodiment 1 of the present invention;

[0023] Figure 4 This is a schematic diagram of beam feedback along the fast axis of a conventional spectral beam combiner.

[0024] Figure 5 This is a schematic diagram of beam feedback in the fast axis direction of the spectral beam combining device of the present invention;

[0025] Figure 6 This is a schematic diagram of a spectral beam combining device for a multi-single-tube semiconductor laser according to Embodiment 2 of the present invention.

[0026] In the picture:

[0027] 1. Linear array semiconductor laser; 2. Fast-axis collimating lens; 3. Slow-axis collimating lens; 4. First cylindrical transmission lens; 5. Diffraction grating; 6. Second cylindrical transmission lens; 7. First concave mirror group; 8. Second concave mirror group. Detailed Implementation

[0028] 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.

[0029] The present invention will now be described in further detail with reference to the accompanying drawings:

[0030] Example 1

[0031] like Figure 1 As shown, the present invention provides a spectral beam combining device for a linear array semiconductor laser, specifically comprising: a linear array semiconductor laser 1, a fast-axis collimating lens 2, a slow-axis collimating lens 3, a first cylindrical transmission lens 4, a diffraction grating 5, a second cylindrical transmission lens 6, a first concave mirror group 7, and a second concave mirror group 8. Both the first concave mirror group 7 and the second concave mirror group 8 include two separate concave mirrors. The fast-axis collimating lens 2, the slow-axis collimating lens 3, the first cylindrical transmission lens 4, the diffraction grating 5, the second cylindrical transmission lens 6, and the first concave mirror 7 are sequentially placed along the optical axis of the laser output from the linear array semiconductor laser 1, and the second concave mirror group 8 is placed along the optical axis of the first-order diffracted beam of the diffraction grating 5.

[0032] In this embodiment, the slow axis of the linear array semiconductor laser 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%. The light-transmitting surfaces of the fast-axis collimating lens 2 and the slow-axis collimating lens 3 are also coated with anti-reflection films with a transmittance ≥99%. These films are used to reduce the beam divergence angle of the laser emitted from the linear array semiconductor laser 1, ensuring that the beam is incident on the cylindrical transmission lens 4 in approximately parallel path.

[0033] The light-transmitting surface of the first cylindrical transmission lens 4 is coated with an anti-reflection film with a transmittance of ≥99%. The distance between the lens and the linear array semiconductor laser 1 and the diffraction grating 5 is the same as the focal length of the lens. It converts the output light of each light-emitting unit of the linear array semiconductor laser 1 into different angles along the slow axis and superimposes it onto the diffraction grating 5. The diffraction grating 5 is placed at a Littrow angle with the optical axis to obtain the highest diffraction efficiency of the grating.

[0034] In the slow axis direction of the linear array semiconductor laser 1, the light beam incident on the diffraction grating 5 undergoes diffraction, with the 0th-order diffracted light passing through the grating 5 and incident on the second cylindrical transmission lens 6 at different angles. The light-transmitting surface of the second cylindrical transmission lens 6 is coated with an anti-reflection film. The focal length of the second cylindrical transmission lens 6 is equal to that of the first cylindrical transmission lens 4, and the distances from the second cylindrical transmission lens 6 to the diffraction grating 5 and the first concave mirror group 7 are both the lens's focal length. The light beam reflected by the first concave mirror group 7 is sequentially incident on the second transmission lens 6 and the diffraction grating 5. Part of the light is transmitted through the diffraction grating 5 and returns to the linear array semiconductor laser 1 as feedback light for wavelength locking. Another part of the light, after diffraction by the diffraction grating 5, is incident on the second concave mirror group 8 and reflected back to the diffraction grating 5; this transmitted light becomes part of the output beam, while the diffracted light returns to the linear array semiconductor laser 1 as feedback light for wavelength locking.

[0035] In the fast axis direction of the linear array semiconductor laser 1, the beam in the fast axis direction is reflected and converged by the curved surface of the separated concave mirror along this direction, and then fed back to the original light-emitting unit.

[0036] The packaging stress of semiconductor laser array chips inevitably leads to the "smile" effect, causing the light emission direction of the light-emitting unit to deviate from the optical axis in the non-spectral beam combining direction (i.e., the fast axis direction of the array). This can result in reduced feedback, wavelength lock-on failure, even failure to form spectral beam combining, and the emission of harmful light. Therefore, such as... Figure 3 As shown, the present invention can maximize the light power fed back to the original light-emitting unit by adjusting the two concave mirrors of the first concave mirror group 7 and the second concave mirror group 8. At this time, the angles of each mirror are optimal, achieving stable wavelength locking and spectral beam combining. The combined laser is output along the -1st order diffraction direction of the grating.

[0037] Figure 4 This is a schematic diagram of beam feedback in the fast axis direction of a conventional spectral beam combiner. In the fast axis direction, only the fast axis collimating mirror 2 of the linear array semiconductor laser 1 has a collimating effect. When the beam is fed back to the original light-emitting unit via the plane mirror 9, the divergence radius of the beam in the fast axis direction is much larger than the size of the light-emitting unit. Only a portion of the beam participates in wavelength locking. When the linear array semiconductor laser 1 has a significant "smile" effect, the beam cannot be locked.

[0038] Figure 5 This is a schematic diagram of the beam feedback in the fast axis direction of the spectral beam combining device proposed in this invention. The curved surface of the first concave mirror group 7 along the fast axis direction converges the fast axis of the feedback beam, allowing more beams to return to the original light-emitting unit to participate in wavelength locking. Furthermore, the separated concave mirrors can adjust their angles according to the "smile" effect, thereby making the wavelength locking of the light-emitting unit more stable and achieving stable spectral beam combining.

[0039] Example 2

[0040] like Figure 6 As shown, this invention provides a spectral beam combining device for multiple single-tube semiconductor lasers, specifically comprising: multiple single-tube semiconductor lasers arranged horizontally in a linear fashion, equivalent to the linear array semiconductor laser 1 in Embodiment 1; a fast-axis collimating lens 2, a slow-axis collimating lens 3, a first cylindrical transmission lens 4, a diffraction grating 5, a second cylindrical transmission lens 6, and a first concave mirror group 7 placed sequentially along the optical axis of the output laser beams of the multiple single-tube semiconductor lasers; the diffraction grating 5 is placed at a Littrow angle to the optical axis; and the second concave mirror group 8 is placed on the optical axis of the first-order diffracted beam of the diffraction grating 5. The front cavity surface of the single-tube semiconductor lasers is coated with an anti-reflection film with a transmittance ≥99%. All lenses have anti-reflection films on their light-transmitting surfaces, with a transmittance ≥99%, and the mirrors are coated with high-reflection films, with a reflectance ≥99%. The first cylindrical transmission lens 4 and the second cylindrical transmission lens 6 have the same focal length, forming a telescope system. The multi-single-tube semiconductor laser 1, the diffraction grating 5, and the first concave mirror group 7 are respectively placed on the focal plane of the first cylindrical transmission lens 4 and the second cylindrical transmission lens 6.

[0041] Adjust the two concave mirrors of the first concave mirror group 7 and the second concave mirror group 8 to maximize the light power fed back to the original light-emitting unit. At this time, their respective angles are optimal, achieving stable wavelength locking and spectral beam combining. The combined laser is output along the -1st order diffraction direction of the grating.

[0042] 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 device for a linear array semiconductor laser, characterized in that, include: A linear array semiconductor laser and a fast-axis collimating lens, a slow-axis collimating lens, a first cylindrical transmission lens, and a diffraction grating are sequentially arranged along the optical axis of the linear array semiconductor laser. A second cylindrical transmission lens and a first concave mirror group are sequentially arranged in the direction of the 0th order diffraction beam of the diffraction grating, and a second concave mirror group is arranged in the direction of the 1st order diffraction beam. The -1st order diffracted light of the diffraction grating is used as the output light. The angles of the first concave mirror group and the second concave mirror group are adjustable. The linear array semiconductor laser and the diffraction grating are disposed on the focal plane of the first cylindrical transmission lens, and the first concave mirror group and the diffraction grating are disposed on the focal plane of the second cylindrical transmission lens; the first concave mirror group and the second concave mirror group reflect the diffracted beam incident on them and feed it back to the linear array semiconductor laser to form external cavity wavelength locking. Both the first and second concave mirror groups include two separate concave mirrors. The two separate concave mirrors are obtained by separating a single concave mirror from the center along the fast axis of the linear array semiconductor laser. The two separate concave mirrors adjust their angles according to the "smile" effect of the linear array semiconductor laser, so that the feedback light returns to the corresponding light-emitting unit of the linear array semiconductor laser to form effective feedback. At the same time, the curved surface of the first concave mirror group converges the diverging beam in the fast axis direction along the fast axis direction of the linear array semiconductor laser, so that the beam is fed back to the original light-emitting unit.

2. The spectral beam combining device for a linear array semiconductor laser as described in claim 1, characterized in that, The front cavity surface of the linear array semiconductor laser is coated with an anti-reflection film with a transmittance of ≥99%.

3. The spectral beam combining device for a linear array semiconductor laser as described in claim 1, 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%.

4. The spectral beam combining device for a linear array semiconductor laser as described in claim 1, characterized in that, The diffraction grating is positioned at the Littrow angle relative to the optical axis.

5. The spectral beam combining device for a linear array semiconductor laser as described in claim 1, characterized in that, Both the first and second cylindrical transmission lenses have anti-reflective coatings on their light-transmitting surfaces, with a transmittance ≥99%; the focal lengths of the first and second cylindrical transmission lenses are... f Same, forming 4 f A telephoto telescope system; the first cylindrical transmission lens superimposes the light beams emitted by each light-emitting unit on the linear array semiconductor laser onto the diffraction grating, and the second cylindrical transmission lens superimposes the feedback light beam onto the diffraction grating.

6. The spectral beam combining device for a linear array semiconductor laser as described in claim 1, characterized in that, The first and second concave mirror groups are coated with a high-reflectivity film with a reflectivity >99%.

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