A narrow linewidth spectral beam combining device for array semiconductor lasers

Abstract

The present invention discloses a narrow linewidth spectral beam combining device for an array semiconductor laser, comprising: an array semiconductor laser, a fast axis collimator, a slow axis collimator, a rhombus prism combination, a cylindrical transmission lens, a diffraction grating, and an output coupling mirror arranged in sequence along the laser transmission direction; the array semiconductor laser and the diffraction grating are respectively located on the front and rear focal planes of the cylindrical transmission lens, and the output coupling mirror is placed in the output direction of the ‑1st order diffraction light of the diffraction grating and is perpendicular to the ‑1st order diffraction light; the rhombus prism combination divides and rearranges the slow axis direction light beam emitted by the array semiconductor laser, and after a row of light beams is divided and rearranged by two groups of rhombus prisms, it is converted into multiple partial light beams arranged equidistantly in the fast axis direction; the cylindrical transmission lens converts the multiple partial light beams into different angles incident on the diffraction grating, and after being diffracted by the diffraction grating, they are incident on the output coupling mirror. The present invention can achieve narrow linewidth spectral beam combining output in a small volume and with high stability.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor laser technology, and in particular to a narrow linewidth spectrum combining device for array semiconductor lasers. Background Art

[0002] Semiconductor lasers offer numerous advantages, including high efficiency, compact size, long life, a wide range of wavelengths, and the ability to be directly electrically driven. However, their beam quality and the output power of individual light-emitting units significantly limit their applications. External cavity feedback spectral beam combining is an effective method for improving the brightness and beam quality of semiconductor laser arrays, significantly enhancing their performance.

[0003] External cavity spectral combining enables simultaneous spatial overlap of multiple laser beams in the near and far fields, combining them into a single aperture output. The combined beam quality approaches that of a single light-emitting unit, and the output power is N times that of a single light-emitting unit. However, due to grating dispersion and external cavity feedback, each laser unit oscillates at a different wavelength, resulting in a broadened overall linewidth after combining. Therefore, the application of spectral combining technology for array semiconductor lasers is very limited in applications requiring narrow linewidth, such as pump lasers.

[0004] Usually, high-power spectral beam combining output requires the participation of multiple array semiconductor lasers in the beam combining. However, the overall linewidth of the output beam after the spectral beam combining of a single array semiconductor laser determines the number of array semiconductor lasers that can participate in the spectral beam combining. Moreover, the overall linewidth increases with the increase in the number of array semiconductor lasers participating in the spectral beam combining. If the spectral beam combining linewidth of a single array semiconductor laser is too wide, the number of semiconductor laser arrays that the gain bandwidth allows to participate in the spectral beam combining will decrease. At the same time, the high diffraction efficiency of the grating only exists in a certain wavelength range. The more the number of array semiconductor lasers participating in the spectral beam combining increases, the further the wavelength deviates from the maximum diffraction efficiency of the grating, and the lower the overall spectral beam combining efficiency will be. If the spectral beam combining of multiple array semiconductor lasers is achieved at the expense of efficiency, the advantage of the high conversion efficiency of the semiconductor laser will not be realized. Therefore, achieving narrow linewidth output after spectral beam combining of a single array semiconductor laser becomes the key to achieving spectral beam combining of multiple array semiconductor lasers.

[0005] At present, in order to obtain narrow-linewidth spectral beam combining output, long-focal-length transmission lenses, high-line-density diffraction gratings, and grating alignment methods are generally used to compress the spectral linewidth. However, these methods will cause negative effects such as a significant increase in the external cavity length, a decrease in beam combining efficiency, and an increase in cost. Summary of the Invention

[0006] In response to the shortcomings of the prior art, the present invention provides a narrow-linewidth spectral beam combining device for array semiconductor lasers. By introducing a rhombus prism combination in an external cavity, the device splits and rearranges the light beam emitted by the array semiconductor laser, shortening the beam width in the spectral beam combining direction by about 2 / 3, thereby effectively compressing the spectral beam combining linewidth by about 2 / 3, providing a new solution for achieving narrowing of the spectral beam combining linewidth of array semiconductor lasers and miniaturization of the system.

[0007] The present invention discloses a narrow linewidth spectrum combining device for array semiconductor lasers, comprising: an array semiconductor laser, a fast axis collimator, a slow axis collimator, a rhombus prism assembly, a cylindrical transmission lens, a diffraction grating and an output coupling mirror arranged in sequence along the laser transmission direction;

[0008] The array semiconductor laser and the diffraction grating are respectively located on the front and rear focal planes of the cylindrical transmission lens, and the output coupling mirror is placed in the output direction of the -1 order diffraction light of the diffraction grating and is perpendicular to the -1 order diffraction light;

[0009] The rhombus prism combination splits and rearranges the slow-axis direction light beam emitted by the array semiconductor laser, and the slow-axis direction is the spectral beam combining direction; after a row of light beams is split and rearranged by two groups of rhombus prisms, it is converted into multiple partial light beams arranged equidistantly in the fast-axis direction, shortening the width of the light beam in the slow-axis direction by 2 / 3; the cylindrical transmission lens converts the multiple partial light beams into different angles and incident on the diffraction grating, and then incident on the output coupling mirror after diffraction by the diffraction grating.

[0010] As a further improvement of the present invention, the rhombic prism assembly comprises two groups;

[0011] The first group includes a plurality of rhombic prisms arranged in parallel in the slow axis direction, and is used to split the slow axis direction light beam emitted by the array semiconductor laser into multiple parts, with one side light beam offset upward and the other side light beam offset downward relative to the middle part light beam, and the offset amounts on both sides are equal;

[0012] The second group consists of multiple rhombic prisms staggered in the fast axis direction, which shift the two side beams equidistantly in the slow axis direction, so that the exit positions of the two side beams coincide with the middle beam in the fast axis direction;

[0013] A row of light beams in the slow axis direction emitted by the array semiconductor laser is divided and rearranged by two groups of rhombus prisms, and is converted into multiple light beams arranged equidistantly in the fast axis direction.

[0014] Furthermore, the first group and the second group each contain three rhombic prisms. After a row of light beams emitted in the slow axis direction from the array semiconductor laser are split and rearranged by the two groups of rhombic prisms, they are converted into three light beams equidistantly arranged in the fast axis direction. At this time, the width of the light beam in the slow axis direction is shortened by about 2 / 3 compared with the original.

[0015] As a further improvement of the present invention, the light-transmitting surfaces of the rhombus prisms are all coated with anti-reflection films, with a transmittance of ≥99%.

[0016] As a further improvement of the present invention, the front cavity surface of the array semiconductor laser is coated with an anti-reflection film with a transmittance of ≥99% to reduce the influence of intracavity feedback and better achieve external cavity wavelength locking; the array semiconductor laser includes but is not limited to one of a linear array semiconductor laser and a stacked array semiconductor laser.

[0017] As a further improvement of the present invention, the fast-axis collimator is a cylindrical microlens, and the slow-axis collimator is a cylindrical microlens array; the light-passing surfaces of the fast-axis collimator and the slow-axis collimator are both coated with an anti-reflection film with a transmittance ≥ 99%; the fast-axis collimator and the slow-axis collimator respectively collimate the fast and slow axes of the laser output by the linear array semiconductor laser to reduce the beam divergence angle.

[0018] As a further improvement of the present invention, in the spectral beam combining direction, the cylindrical transmission lens superimposes the light beam split and rearranged by the rhombus prism combination onto the diffraction grating, and the light-transmitting surface is coated with an anti-reflection film with a transmittance of ≥99%.

[0019] As a further improvement of the present invention, the diffraction grating is placed at a Littrow angle with the optical axis, and the polarization direction of the light beam of the array semiconductor laser matches the diffraction polarization direction of the diffraction grating to achieve high diffraction efficiency; the diffraction grating includes but is not limited to one of a reflective diffraction grating and a transmissive diffraction grating.

[0020] As a further improvement of the present invention, the output coupling mirror feeds a portion of the -1 order diffraction beam back to the original light-emitting unit to achieve wavelength locking, and the remaining portion of the beam is emitted as the output beam. Compared with the prior art, the present invention has the following beneficial effects:

[0021] The spectral beam combining device of the present invention can achieve narrow linewidth spectral beam combining output when using a short focal length cylindrical transmission lens, greatly shortening the external cavity length of the beam combining structure and improving the reliability and stability of the beam combining structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for the embodiments or the description of the prior art. It should be understood that the following drawings only illustrate certain embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Therefore, they should not be regarded as limiting the scope. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without inventive effort.

[0023] Figure 1 This is a three-dimensional schematic diagram of a narrow-linewidth spectral beam combining device for a linear array semiconductor laser according to Example 1 of the present invention;

[0024] Figure 2 A top view of a narrow-linewidth spectral beam combining device for a linear array semiconductor laser according to Example 1 of the present invention;

[0025] Figure 3 Schematic diagram of beam splitting and rearrangement of the rhombus prism combination in Example 1 of the present invention;

[0026] Figure 4 Schematic diagram of the front view of the beam splitting and rearrangement of the rhombus prism combination in Example 1 of the present invention;

[0027] Figure 5 Schematic diagram of light spot changes in the narrow linewidth spectral beam combining device of the linear array semiconductor laser according to Example 1 of the present invention;

[0028] Figure 6 This is a three-dimensional schematic diagram of a narrow linewidth spectral beam combining device of a stacked array semiconductor laser according to Example 2 of the present invention;

[0029] Figure 7 Schematic diagram of the light spot change in the narrow linewidth spectral beam combining device of stacked semiconductor laser arrays according to Example 2 of the present invention.

[0030] In the picture:

[0031] 1. Linear array semiconductor laser or stacked array semiconductor laser; 2. Fast axis collimator; 3. Slow axis collimator; 4. Rhombic prism combination; 5. Cylindrical transmission lens; 6. Diffraction grating; 7. Output coupling mirror. DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0033] The present invention is described in further detail below with reference to the accompanying drawings:

[0034] Example 1

[0035] like Figure 1 、 2 As shown, the present invention provides a narrow-linewidth spectral beam combining device for a linear array semiconductor laser, specifically comprising: a linear array semiconductor laser 1, a fast-axis collimator 2, a slow-axis collimator 3, an rhombus prism assembly 4, a cylindrical transmission lens 5, a diffraction grating 6, and an output coupling mirror 7. The fast-axis collimator 2, the slow-axis collimator 3, the rhombus prism assembly 4, the cylindrical transmission lens 5, and the diffraction grating 6 are sequentially arranged along the optical axis of the linear array semiconductor laser 1. The output coupling mirror 7 is placed in the output direction of the -1st order diffraction light of the diffraction grating 6 and is perpendicular to the -1st order diffraction light. The spectral beam combining direction is the slow-axis direction, along the horizontal direction (x-axis).

[0036] In this embodiment:

[0037] The slow axis of the linear array semiconductor laser 1 is along the horizontal direction (x-axis), and the fast axis is perpendicular to the horizontal direction (y-axis). The front cavity surface is coated with an anti-reflection film with a transmittance of ≥99%.

[0038] The light-transmitting surfaces of the fast-axis collimator 2 and the slow-axis collimator 3 are coated with an anti-reflection film with a transmittance of ≥99%, and are used to collimate the laser light emitted by the linear array semiconductor laser 1 and reduce the beam divergence angle.

[0039] The rhombus prism assembly 4 is placed between the linear array semiconductor laser 1 and the cylindrical transmission lens 5. The rhombus prism assembly 4 splits and rearranges the slow-axis light beam emitted by the linear array semiconductor laser 1. After passing through two groups of rhombus prisms, a row of light beams is converted into three equidistant light beams arranged in the fast-axis direction, shortening the width of the light beam in the slow-axis direction by approximately 2 / 3. The light-transmitting surfaces of the rhombus prism assembly 4 are all coated with an anti-reflection coating, with a transmittance of ≥99%.

[0040] The light-transmitting surface of the cylindrical transmission lens 5 is coated with an anti-reflection film with a transmittance of ≥99%. The distance from the linear array semiconductor laser 1 and the diffraction grating 6 is one times the focal length of the lens. It converts the three parts of the light beam along the slow axis after the rhombus prism combination splits and rearranges them into four parts and superimposes them on the diffraction grating 6 at different angles.

[0041] The diffraction grating 6 is placed at a Littrow angle with the optical axis. The polarization direction of the light beam of the linear array semiconductor laser 1 should match the diffraction polarization direction of the diffraction grating 6 to obtain high diffraction efficiency of the grating. The diffraction grating 6 can be a transmission diffraction grating or a reflection diffraction grating.

[0042] The output coupling mirror 7 feeds back a portion of the -1st order diffraction light beam to the original light emitting unit to achieve wavelength locking, and the remaining -1st order diffraction light is used as the output laser.

[0043] like Figure 3 、 4 As shown, the rhombus prism assembly 4 comprises two groups. The first group comprises three rhombus prisms arranged parallel to the slow axis. These split the slow-axis beam emitted by the linear array semiconductor laser 1 into three parts. Relative to the center beam, one beam is offset upward, while the other is offset downward, with equal offsets on both sides. The second group comprises three rhombus prisms staggered along the fast axis, which shift the two beams equidistantly along the slow axis, so that the exit positions of the two beams coincide with the center beam along the fast axis. Ultimately, after being split and rearranged by the two groups of rhombus prisms, the row of slow-axis beams emitted by the linear array semiconductor laser 1 is converted into three beams equidistantly arranged along the fast axis.

[0044] like Figure 5 As shown in the figure, a1 is the light spot diagram emitted by the linear array semiconductor laser 1, a2 is the light spot after being divided by the first group of rhombus prisms, a3 is the light spot after being divided by the second group of rhombus prisms, and a4 is the light spot diagram output by the spectral beam combination.

[0045] Example 2

[0046] like Figure 6 As shown, the present invention provides a three-dimensional schematic diagram of a stacked semiconductor laser narrow linewidth spectral beam combining device, which specifically includes: a stacked semiconductor laser 1, a fast-axis collimator 2, a slow-axis collimator 3, an rhombus prism assembly 4, a cylindrical transmission lens 5, a diffraction grating 6, and an output coupling mirror 7; the fast-axis collimator 2, the slow-axis collimator 3, the rhombus prism assembly 4, the cylindrical transmission lens 5, and the diffraction grating 6 are arranged in sequence along the optical axis of the stacked semiconductor laser 1, and the output coupling mirror 7 is placed in the output direction of the -1 order diffraction light of the diffraction grating 6 and is perpendicular to the -1 order diffraction light; the spectral beam combining direction is the slow-axis direction, along the horizontal direction (x-axis).

[0047] In this embodiment:

[0048] The front cavity surface of the stacked semiconductor laser array 1 is anti-reflection coated with a transmittance of ≥99%. The light-passing surfaces of the rhombic prism 4 and cylindrical transmission lens 5 are also anti-reflection coated with a transmittance of ≥99%. The rhombic prism assembly 4 is placed between the stacked semiconductor laser array 1 and the cylindrical transmission lens 5. The distance between the cylindrical transmission lens 5 and the stacked semiconductor laser array 1 and the diffraction grating 6 is one lens focal length. The diffraction grating 6 is positioned at the Littrow angle with respect to the optical axis. The output coupling mirror 7 feeds a portion of the -1st order diffracted light back to the original light-emitting unit to achieve wavelength locking. The remaining -1st order diffracted light serves as the output laser.

[0049] Unlike Example 1, the stacked semiconductor laser array 1 has multiple arrays arranged equidistantly along the fast axis, with non-luminous regions spaced a certain distance apart between each array. Using a rhombus prism assembly 4 to split and rearrange the beams fills the non-luminous regions between the stacked arrays. This shortens the beam width in the spectral combining direction to achieve a narrow linewidth while maintaining essentially unchanged beam quality in the fast axis after spectral combining.

[0050] like Figure 7 As shown in the figure, b1 is the light spot diagram emitted by the stacked array semiconductor laser 1, b2 is the light spot after being divided by the first group of rhombus prisms, b3 is the light spot after being divided by the second group of rhombus prisms, and b4 is the light spot diagram of the spectral beam combination output.

[0051] The advantages of the present invention are:

[0052] The external cavity spectral beam combining device of the present invention introduces a rhombus prism combination into the external cavity to split and rearrange the light beam emitted by the array semiconductor laser, shortening the beam width in the spectral beam combining direction by about 2 / 3, thereby effectively compressing the spectral beam combining linewidth by about 2 / 3, so that the overall structure can achieve narrow linewidth spectral beam combining output in a small volume and high stability.

[0053] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A narrow linewidth spectral beam combining device for array semiconductor lasers, characterized in that: include: An array semiconductor laser, a fast axis collimator, a slow axis collimator, a rhombus prism assembly, a cylindrical transmission lens, a diffraction grating and an output coupling mirror are sequentially arranged along the laser transmission direction; The array semiconductor laser and the diffraction grating are respectively located on the front and rear focal planes of the cylindrical transmission lens, and the output coupling mirror is placed in the output direction of the -1 order diffraction light of the diffraction grating and is perpendicular to the -1 order diffraction light; The rhombus prism assembly divides and rearranges the light beams in the slow axis direction emitted by the array semiconductor laser, where the slow axis direction is the spectral beam combining direction; after a row of light beams is divided and rearranged by two sets of rhombus prisms, it is converted into multiple partial light beams arranged equidistantly in the fast axis direction; the cylindrical transmission lens converts the multiple partial light beams into different angles and makes them incident on the diffraction grating, which then diffracts the light beams and makes them incident on the output coupling mirror. The rhombus prism assembly comprises two groups; The first group includes a plurality of rhombic prisms arranged in parallel in the slow axis direction, and is used to split the slow axis direction light beam emitted by the array semiconductor laser into multiple parts, with one side light beam offset upward and the other side light beam offset downward relative to the middle part light beam, and the offset amounts on both sides are equal; The second group consists of multiple rhombic prisms staggered in the fast axis direction, which shift the two side beams equidistantly in the slow axis direction, so that the exit positions of the two side beams coincide with the middle beam in the fast axis direction; A row of light beams in the slow axis direction emitted by the array semiconductor laser is divided and rearranged by two groups of rhombus prisms, and is converted into multiple light beams arranged equidistantly in the fast axis direction.

2. The narrow linewidth spectral beam combining device of array semiconductor laser according to claim 1, characterized in that: The first group and the second group each include three rhombus prisms. A row of light beams in the slow axis direction emitted by the array semiconductor laser are divided and rearranged by the two groups of rhombus prisms and converted into three light beams equidistantly arranged in the fast axis direction.

3. The narrow linewidth spectral beam combining device of array semiconductor lasers according to claim 1, characterized in that: The light-transmitting surfaces of the rhombus prism are all coated with anti-reflection films, with a transmittance of ≥99%.

4. The narrow linewidth spectral beam combining device of an array semiconductor laser according to any one of claims 1 to 2, characterized in that: The front cavity surface of the array semiconductor laser is coated with an anti-reflection film, and the transmittance is ≥99%; the array semiconductor laser includes but is not limited to one of a linear array semiconductor laser and a stacked array semiconductor laser.

5. The narrow linewidth spectral beam combining device of an array semiconductor laser according to any one of claims 1 to 2, characterized in that: The fast-axis collimator is a cylindrical microlens, and the slow-axis collimator is a cylindrical microlens array; the light-transmitting surfaces of the fast-axis collimator and the slow-axis collimator are both coated with anti-reflection films with a transmittance of ≥99%.

6. The narrow linewidth spectral beam combining device of an array semiconductor laser according to any one of claims 1 to 2, characterized in that: In the direction of spectral beam combining, the cylindrical transmission lens superimposes the light beams split and rearranged by the rhombus prism combination onto the diffraction grating, and the light-transmitting surface is coated with an anti-reflection film with a transmittance of ≥99%.

7. The narrow linewidth spectral beam combining device of an array semiconductor laser according to any one of claims 1 to 2, characterized in that: The diffraction grating is placed at a Littrow angle with the optical axis, and the polarization direction of the light beam of the array semiconductor laser matches the diffraction polarization direction of the diffraction grating.

8. The narrow linewidth spectral beam combining device of array semiconductor lasers according to claim 7, characterized in that: The diffraction grating includes but is not limited to one of a reflective diffraction grating and a transmissive diffraction grating.

9. The narrow linewidth spectral beam combining device of an array semiconductor laser according to any one of claims 1 to 2, characterized in that: The output coupling mirror feeds a partial proportion of the -1 order diffraction light beam back to the original light emitting unit to achieve wavelength locking, and the remaining proportion of the light beam is emitted as the output light beam.

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