Laser spectral width compression device

Abstract

The utility model relates to the technical field of semiconductor lasers, in particular to a laser spectral width compression device, which comprises a plurality of laser units, a collimating lens group, a conversion lens group, a diffraction grating and an output coupling mirror. And the parallel light group enters the conversion lens group for spectral width compression, so that laser in the parallel light group enters the same position of the diffraction grating at different angles and is diffracted to the output coupling mirror by the diffraction grating at the same angle. According to the utility model, the spectral width of the combined laser is compressed through the conversion lens group, so that more laser units can be combined in a limited space, and the output power is effectively improved on the premise of not increasing the whole optical path.

Description

Technical Field

[0001] The utility model relates to the technical field of semiconductor lasers, and particularly provides a laser spectral width compression device. Background Art

[0002] Semiconductor laser spectral beam combining is a technology that uses optical dispersion elements and an external cavity feedback structure to combine the beams of multiple semiconductor laser units to output with a common aperture to achieve high-power output. According to the grating diffraction and external cavity feedback principles, the unit beams of the semiconductor lasers are focused onto the grating by a transmission lens at different incident angles, form oscillations in the resonant cavity through an output coupling mirror, and finally are locked to output at different wavelengths with the same diffraction angle. Spectral beam combining has no strict restrictions on the characteristics of sub-beams such as wavelength, phase, and beam quality, and has the advantages of simple principle structure, stable system, and high beam combining efficiency. Therefore, it has been widely favored by researchers at home and abroad and has gradually become a research hotspot in the field of modern high-energy lasers.

[0003] Due to the limited gain bandwidth of semiconductor lasers, when performing wavelength locking of the external cavity for the light-emitting units in spectral beam combining, it is necessary to consider the problem of the center wavelength interval between adjacent emission units participating in beam combining to avoid unsuccessful wavelength locking caused by limited gain bandwidth. The factors affecting the center wavelength interval of the emission units mainly include the grating constant, the distance between adjacent laser units in the semiconductor laser array, and the focal length of the transmission lens. According to the formula for the center wavelength interval between adjacent units in the spectral beam combining system, the longer the focal length of the transmission lens, the smaller the center wavelength interval between adjacent units, which is undoubtedly beneficial for achieving beam combining of more laser units. However, the focal length of the transmission lens also affects the optical path of the entire spectral beam combining. An overly long optical path will not only affect the alignment difficulty but also have an impact on the beam combining efficiency of the beam and the beam quality of the output beam. Summary of the Utility Model

[0004] To solve the above problems, the utility model provides a laser spectral width compression device. Based on the existing laser spectral beam combining system, the spectral width of the beam is compressed by a conversion lens group, and the optical path of the spectral beam combining is reduced, which not only realizes the high-power output of the semiconductor laser but also realizes the miniaturization of the laser system.

[0005] The laser spectral width compression device provided by the utility model includes:

[0006] A plurality of laser units, which are arranged in the order of wavelength size, wherein the laser output directions of the laser units are the same, and the intervals between the laser units are the same;

[0007] Along the laser optical path of the laser units, a collimating lens group, a conversion lens group, a diffraction grating, and an output coupling mirror are sequentially provided;

[0008] Among them, the collimating lens group collimates the laser output by the laser unit to obtain a parallel light group; the parallel light group enters the conversion lens group, and the conversion lens group compresses the spectral width of the parallel light group, so that the lasers in the parallel light group are incident on the same position of the diffraction grating at different angles and are diffracted by the diffraction grating to the output coupling mirror at the same angle.

[0009] Preferably, the laser unit is a semiconductor laser.

[0010] Preferably, a plurality of laser units are a bar including a plurality of single-tube lasers.

[0011] Preferably, the collimating lens group includes a fast-axis collimating mirror and a slow-axis collimating mirror.

[0012] Preferably, the conversion lens group includes a first cylindrical conversion lens and a second cylindrical conversion lens. The first cylindrical conversion lens is a positive lens, and the second cylindrical conversion lens is a negative lens.

[0013] Preferably, the distance between the first cylindrical conversion lens and the second cylindrical conversion lens is d, and d = L / 2, where L represents the distance between the first cylindrical conversion lens and the diffraction grating;

[0014] The focal length f1 of the first cylindrical conversion lens is:

[0015]

[0016] where f represents the focal length of the conversion lens group;

[0017] The focal length f2 of the second cylindrical conversion lens is:

[0018]

[0019] Preferably, the aperture number F1 of the first cylindrical conversion lens is:

[0020]

[0021] where F represents the aperture number of the conversion lens group;

[0022] The aperture number F2 of the second cylindrical conversion lens is:

[0023]

[0024] Preferably, the conversion lens group includes a third cylindrical conversion lens. The third cylindrical conversion lens is a positive lens and is used to converge the laser.

[0025] Compared with the prior art, the present utility model can achieve the following beneficial effects:

[0026] The utility model compresses the spectral width of the combined laser by adding a conversion lens group to the existing laser beam combination system, reduces the optical path of the combined laser, enables more laser units to be combined within a limited spectral width, further improves the output power of spectral beam combination while reducing the overall optical path of the beam, reduces the alignment difficulty of each optical element in the system, and meets the miniaturization requirement of the laser beam combination module. Brief Description of the Drawings

[0027] Figure 1 is a structural diagram of a laser spectral width compression device provided in Embodiment 1 of the present utility model;

[0028] Figure 2 is a side view of a laser spectral width compression device provided in Embodiment 1 of the present utility model;

[0029] Figure 3 is a structural diagram of a laser spectral width compression device provided in Embodiment 2 of the present utility model;

[0030] Figure 4 is a structural diagram of a laser spectral width compression device provided in Embodiment 3 of the present utility model.

[0031] The reference numerals therein include:

[0032] Laser unit 10, fast-axis collimating mirror 20, slow-axis collimating mirror 30, first cylindrical conversion lens 40, second cylindrical conversion lens 50, diffraction grating 60, output coupling mirror 70, third cylindrical conversion lens 80. Detailed Description of the Embodiments

[0033] In the following, embodiments of the present utility model will be described with reference to the drawings. In the following description, the same modules are denoted by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, their detailed descriptions will not be repeated.

[0034] In order to make the objectives, technical solutions and advantages of the present utility model clearer, the present utility model will be further described in detail below with reference to the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present utility model and do not constitute a limitation to the present utility model.

[0035] Embodiment 1:

[0036] As Figure 1 and Figure 2As shown in the figure, the laser spectral width compression device provided by the first embodiment of the present invention includes: four laser units 10, a collimating lens group, a conversion lens group, a diffraction grating 60, and an output coupling mirror 70. Among them, the four laser units 10 are all laser single tubes, which are used to emit laser light to achieve spectral beam combining. In addition, the number of laser units 10 can be specifically designed according to requirements, such as Figure 2 101-10N in

[0037] represents multiple laser units 10. In this embodiment, the four laser units are all semiconductor lasers, and they are arranged in the order of the wavelengths of the emitted laser light, and are arranged in parallel and at equal intervals. The output directions of the laser lights of the four laser units are the same, and the four light beams are arranged in a one-dimensional equidistant manner and are symmetric about the optical axis. The four light beams form a parallel light group. Along the propagation optical path of the parallel light group, a collimating lens group, a conversion lens group, a diffraction grating 60, and an output coupling mirror 70 are sequentially arranged.

[0038] The collimating lens group includes a fast-axis collimating mirror 20 and a slow-axis collimating mirror 30. The fast-axis collimating mirror 20 and the slow-axis collimating mirror 30 are both perpendicular to the beam propagation direction of the parallel light group. The output beams of the four laser units 10 first pass through the fast-axis collimating mirror 20. The fast-axis collimating mirror 20 collimates the four light beams in the fast-axis direction and compresses the divergence angle of the light beams. After being collimated by the fast-axis collimating mirror 20, the parallel light group passes through the slow-axis collimating mirror 30. The slow-axis collimating mirror 30 collimates the four light beams in the slow-axis direction and compresses the divergence angle of the light beams, further improving the linearity and uniformity of the light beams. After the above collimation process, the four light beams obtain a parallel light group. This parallel light group continues to be transmitted to the conversion lens group for spectral width compression.

[0038] The conversion lens group includes a first cylindrical conversion lens 40 and a second cylindrical conversion lens 50. The optical power of the first cylindrical conversion lens 40 is positive, that is, it is a positive lens, and the optical power of the second cylindrical conversion lens 50 is negative, that is, it is a negative lens. The distance between the first cylindrical conversion lens 40 and the second cylindrical conversion lens 50 is d, and the distance between the first cylindrical conversion lens 40 and the diffraction grating 60 is L. Then the position requirements for the first cylindrical conversion lens 40 and the second cylindrical conversion lens 50 are:

[0039] d = L / 2.

[0040] According to the position requirements, the focal length f1 of the first cylindrical conversion lens 40 and the focal length f2 of the second cylindrical conversion lens 50 can be determined. The specific calculation formulas are as follows:

[0041]

[0042] where f represents the focal length of the conversion lens group.

[0043] The design requirements for the f-number F1 of the first cylindrical conversion lens 40 and the focal length F2 of the second cylindrical conversion lens 50 are as follows:

[0044]

[0045] Among them, F represents the f-number of the conversion lens group.

[0046] In the conversion lens group, the first cylindrical conversion lens 40 is mainly used to compress the spectral width of the light beam. After compression, the second cylindrical conversion lens 50 reshapes the light beam so that the four light beams in the parallel light group can be incident on the same position of the diffraction grating 60 at different angles, that is, the diffraction grating 60 is arranged at the focal position of the four light beams. Then, through the dispersion effect of the diffraction grating 60 on light, the four light beams are diffracted to the coupling mirror 70 at the same angle for spectral beam combination, effectively realizing spectral width compression and reducing the beam combination optical path.

[0047] Embodiment 2:

[0048] As Figure 3 shown, the difference between the laser spectral width compression device provided in Embodiment 2 of the present invention and Embodiment 1 is that: there are two sets of light sources to be combined, that is, the four laser units 10 in Embodiment 1 are replaced with two standard 976nm bars each containing 19 laser units 10, and the intervals between the 19 laser units 10 in each bar are the same. Each bar is correspondingly provided with one fast-axis collimator 20 and one slow-axis collimator 30 to collimate the 38 light beams output from the bar. The collimated parallel light group is then subjected to spectral width compression through the first cylindrical conversion lens 40 and the second cylindrical conversion lens 50, and the compressed spectral width is approximately equal to the spectral width of a single bar. After being converted by the first cylindrical conversion lens 40 and the second cylindrical conversion lens 50, the 38 light beams are incident on the same position of the transmission grating 60 at different angles, and all are diffracted to the output coupling mirror 70 at the same angle through the dispersion effect, and are fed back to each laser unit 10 through the output coupling mirror 70 and locked to different wavelengths to complete spectral beam combination.

[0049] The laser spectral width compression device of Embodiment 2 of the present invention is simulated by Zemax, an experimental model is built, and the beam combination effect is verified. Through actual measurement, it is obtained that: the laser spectral width compression device has obvious effects on the overall optical path and spectral width compression, and at the same time, the output power and laser brightness after final beam combination are also effectively improved. The output power after final beam combination is about 75% of the sum of the powers of all laser units 10. The laser spectral width compression device has a good compression effect on the spectral width and improves the problem of too long optical path during spectral beam combination of the bar array. In Embodiment 2, only two bars are taken as an example, and more bars can be set according to the requirement of output power.

[0050] Embodiment 3:

[0051] As Figure 4 shown, the difference between the laser spectral width compression device provided in Embodiment 3 of the present utility model and Embodiment 1 lies in that: there are 5 laser units 10 provided, and in addition to the first cylindrical conversion lens 40 and the second cylindrical conversion lens 50, the conversion lens group further includes a third cylindrical conversion lens 80. The optical power of the third cylindrical conversion lens 80 is positive, that is, it is a positive lens, which is mainly used for secondary compression of the spectral width of the light beam, further shortening the beam combination optical path, and more laser units 10 can be arranged in a limited space, further improving the output power of the combined laser.

[0052] After the 5 light beams output by the 5 laser units 10 are collimated by the fast-axis collimating mirror 20 and the slow-axis collimating mirror 30, they first pass through the first cylindrical conversion lens 40 transmissively. The spectral width of the light beam is greatly compressed in the spectral beam combination direction, and then passes through the second cylindrical conversion lens 50 transmissively. The second cylindrical conversion lens 50 shapes the compressed light beam. The shaped light beam continues to pass through the third cylindrical conversion lens 80 transmissively. The third cylindrical conversion lens 80 makes the 5 light beams enter the same position of the diffraction grating 60 at different angles and is diffracted by the diffraction grating 60 to the output coupling mirror 70 at the same angle, and the external cavity feedback is completed through the output coupling mirror 70 to realize spectral beam combination.

[0053] Although the embodiments of the present utility model have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present utility model. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present utility model.

[0054] The above specific implementation manners of the present utility model do not constitute a limitation to the protection scope of the present utility model. Any other corresponding changes and deformations made according to the technical concept of the present utility model shall be included in the protection scope of the claims of the present utility model.

Claims

1. A laser spectrum width compression device, characterized in that: include: A plurality of laser units, wherein the laser units are arranged in order of wavelength, wherein the lasers output by the laser units have the same emission direction and the intervals between the laser units are the same; Along the laser optical path of the laser unit, a collimating lens group, a conversion lens group, a diffraction grating and an output coupling mirror are sequentially arranged; The collimating lens group is used to collimate the laser output by the laser unit; the conversion lens group is used to compress the spectral width of the incident laser so that the incident laser is incident to the same position of the diffraction grating at different angles, and the diffraction grating is used to diffract the incident laser to the output coupling mirror at the same angle; The conversion lens group includes a first cylindrical conversion lens and a second cylindrical conversion lens, the first cylindrical conversion lens is a positive lens, and the second cylindrical conversion lens is a negative lens; the distance between the first cylindrical conversion lens and the second cylindrical conversion lens is d, d=L / 2, where L represents the distance between the first cylindrical conversion lens and the diffraction grating; The focal length of the first cylindrical conversion lens for: ； in, represents the focal length of the conversion lens group; The focal length of the second cylindrical conversion lens for: 。 2. The laser spectrum width compression device according to claim 1, characterized in that: The laser unit is a semiconductor laser.

3. The laser spectrum width compression device according to claim 1, characterized in that: The multiple laser units are bars with multiple single-tube lasers built in.

4. The laser spectrum width compression device according to claim 1, characterized in that: The collimating lens group includes a fast-axis collimating lens and a slow-axis collimating lens.

5. The laser spectrum width compression device according to claim 1, characterized in that: The aperture number of the first cylindrical conversion lens for: ； in, represents the aperture number of the conversion lens group; The aperture number of the second cylindrical conversion lens for: 。 6. The laser spectrum width compression device according to claim 1, characterized in that: The conversion lens group includes a third cylindrical conversion lens, and the third cylindrical conversion lens is a positive lens for converging laser light.

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