Optical grating multiplexing spectrum synthesis system

Abstract

The invention belongs to the technical field of laser, and discloses a grating multiplexing spectrum synthesis system, which comprises a beamlet dense array, a diffraction grating and a turn-back mirror, each beamlet emitted by the beamlet dense array is diffracted by the diffraction grating and then is emitted in the form of convergent light, and the light is reflected twice by the turn-back mirror to form a light beam; each laser sub-beam is incident on the diffraction grating again along the opposite direction parallel to the original light, the sub-beams converge into one point on the diffraction grating by adjusting the distance between the turn-back mirror and the diffraction grating, and at the moment, the incident angle of each sub-beam is equal to the diffraction angle diffracted from the diffraction grating for the first time; and the diffraction angles of the sub-beams subjected to the second diffraction on the diffraction grating are equal and equal to the incident angle of the sub-beams subjected to the first diffraction, that is, the synthesized light beam is emitted along the direction parallel to and opposite to the direction of the light beam emitted from the sub-beam dense array. The invention provides a spectrum synthesis system which is simple in structure, easy in engineering implementation and compact in volume.

Description

Technical Field

[0001] The invention belongs to the field of laser technology and relates to a grating multiplexing spectrum synthesis system. Background Art

[0002] Currently, due to the limited output power of single-fiber fiber lasers, it is difficult to meet the high-power laser light source requirements of defense laser weapons. To address this issue, spectrum synthesis has become the most mature and widely used technical solution. Spectral synthesis technology based on multilayer dielectric film gratings is the current mainstream development direction in the field of high-energy laser beam combining. It is mainly divided into two solutions: dual-grating spectrum synthesis and single-grating spectrum synthesis.

[0003] Among them, double-grating spectral synthesis uses two gratings with the same line density to combine multiple parallel incident narrow-linewidth laser sub-beams into one beam. Its advantage is that the incident narrow-linewidth laser sub-beams only need to be incident on the first grating in parallel. Then, by adjusting the distance between the two parallel gratings, the multiple sub-beams of laser are converged on the second grating, and finally diffracted into a high-power combined beam. The structure of the double grating can compensate for the introduced angular dispersion, and the linewidth requirements of the narrow-linewidth laser sub-beams are not high. The disadvantage is that the spatial pitch and azimuth of the two gratings need to remain absolutely parallel, otherwise the beam quality of the combined beam spot will be poor.

[0004] Single-grating spectral synthesis uses a single grating to combine narrow-linewidth laser sub-beams incident at different incident angles into one beam. Its advantage is that only one grating is needed to complete the spectral synthesis of multiple narrow-linewidth laser sub-beams, eliminating the trouble of adjusting the spatial pitch and azimuth parallelism of the two gratings; the disadvantage is that multiple narrow-linewidth laser sub-beams need to be incident strictly according to the predetermined design incident angle, the optical path adjustment is more complicated, and because a single grating cannot compensate for the introduced character dispersion, the line width requirements of the narrow-linewidth laser sub-beams are high, otherwise the beam quality after combining is difficult to guarantee.

[0005] Both dual-grating and single-grating spectral synthesis methods face the common challenges of adjusting the parallelism of the gratings or the incident angle of the sub-beams. Therefore, it is extremely important to develop a spectral synthesis solution that is simple in principle, easy to implement, and provides high beam quality. Summary of the Invention

[0006] (1) Purpose of the invention

[0007] The purpose of the present invention is to provide a grating multiplexing spectrum synthesis system, which solves the problem of grating parallel adjustment or sub-beam laser incident angle adjustment by grating multiplexing.

[0008] (2) Technical solution

[0009] In order to solve the above technical problems, the present invention provides a grating multiplexing spectrum synthesis system, which includes: a sub-beam array 1, a diffraction grating 2 and a returning mirror 3. Each sub-beam emitted by the sub-beam array 1 is diffracted by the diffraction grating 2 and emitted in the form of converged light. After two reflections by a returning mirror 3, each laser sub-beam is incident on the diffraction grating 2 again in the opposite direction parallel to the original light. By adjusting the distance between the returning mirror 3 and the diffraction grating 2, each sub-beam converges to a point on the diffraction grating 2. At this time, the incident angle of each sub-beam is equal to the diffraction angle of the first diffraction from the diffraction grating 2, and the diffraction angle of each sub-beam diffracted for the second time on the diffraction grating 2 is equal, equal to the incident angle of the first diffraction, that is, the synthesized light beam is emitted in a direction parallel to and opposite to the light beam emitted from the sub-beam array 1.

[0010] Furthermore, the dense array of sub-beams 1 is a fiber laser array composed of narrow linewidth laser sub-beams with different central wavelengths and arranged in one dimension.

[0011] Furthermore, the laser sub-beams of the sub-beam array 1 are emitted in parallel.

[0012] Furthermore, the diffraction grating 2 is a reflective grating.

[0013] Furthermore, the diffraction grating 2 is a transmission grating.

[0014] Furthermore, the folding mirror 3 is a single 90° folding mirror.

[0015] Furthermore, the folding mirror 3 is a combination of multiple separate reflecting mirrors.

[0016] Furthermore, according to the grating diffraction equation When the incident angle θ is the same, the central wavelength λ of each beamlet is different, and the diffraction angle Not the same either.

[0017] Furthermore, the sub-beam array 1 emits 5 laser sub-beams with central wavelengths λ of 1062.00nm, 1062.52nm, 1063.03nm, 1063.52nm, and 1064.00nm, respectively. The spacing between adjacent sub-beams is 4mm, and all of them are incident on the diffraction grating 2 at an incident angle of θ=64°, causing diffraction, and the grating line density is 1740line / mm.

[0018] Furthermore, according to the grating diffraction equation Diffraction angle of each laser beam They are 71.64°, 71.80°, 71.97°, 72.13°, and 72.28° respectively; the distance between the position of the movable reflecting mirror 3 and the diffraction grating 2 is 503 mm.

[0019] (3) Beneficial effects

[0020] Compared with the dual-grating spectrum synthesis system and single-grating spectrum synthesis system in the prior art, the laser spectrum synthesis system provided by the present invention avoids the trouble of adjusting the pitch and azimuth parallelism of the two gratings, and does not need to adjust the different incident angles of each laser sub-beam; the present invention combines the advantages of the dual-grating and single-grating spectrum synthesis schemes, adopts the method of parallel incidence of laser sub-beams, single-grating multiplexing, and optical path reversal, and provides a spectrum synthesis system scheme with a simple structure, easy engineering implementation, and compact size. The specific advantages and disadvantages are shown in Table 1 below.

[0021] Table 1 Comparison of advantages and disadvantages of different spectrum synthesis schemes

[0022] BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the reflective grating spectrum synthesis optical path according to an embodiment of the present invention;

[0024] Figure 2 Schematic diagram of the transmission grating spectrum synthesis optical path of an embodiment of the present invention. DETAILED DESCRIPTION

[0025] In order to make the purpose, content and advantages of the present invention more clear, the specific implementation methods of the present invention are further described in detail below with reference to the accompanying drawings and examples.

[0026] Reference Figure 1 and Figure 2 As shown, the spectral synthesis system of the grating multiplexing in this embodiment includes a sub-beam array 1, a diffraction grating 2 and a returning mirror 3. Each sub-beam emitted by the sub-beam array 1 is diffracted by the diffraction grating 2 and emitted in the form of convergent light. After two reflections by a returning mirror 3, each laser sub-beam is incident on the diffraction grating 2 again in the opposite direction parallel to the original light. By adjusting the distance between the returning mirror 3 and the diffraction grating 2, each sub-beam converges to a point on the diffraction grating 2. At this time, the incident angle of each sub-beam is equal to the diffraction angle of the first diffraction from the diffraction grating 2, and the diffraction angle of each sub-beam at the second diffraction on the diffraction grating 2 is equal, which is equal to the incident angle at the first diffraction, that is, the synthesized light beam is emitted in a direction parallel to and opposite to the light beam emitted from the sub-beam array 1.

[0027] The sub-beam array 1 is a fiber laser array composed of narrow linewidth laser beams with different central wavelengths and arranged in one dimension, and each laser beam is emitted in parallel.

[0028] The diffraction grating 2 diffracts the narrow linewidth lasers of different wavelengths emitted by the sub-beam array 1, which are then reflected back by the returning mirror 3 and incident on the surface of the diffraction grating 2 again. By adjusting the distance between the returning mirror 3 and the diffraction grating 2, the laser sub-beams converge on the surface of the diffraction grating 2 and are diffracted and emitted again by the diffraction grating 2. The grating multiplexing method is used to achieve a spectral synthesis effect with high beam quality.

[0029] The diffraction grating 2 is a reflective grating or a transmissive grating.

[0030] The folding mirror 3 is a single 90° folding mirror, or a combination of multiple separate reflecting mirrors.

[0031] The sub-beam array 1 emits narrow linewidth fiber lasers with different central wavelengths and keeps them parallel to each other. They are incident on the diffraction grating 2 at the same incident angle. According to the grating diffraction equation When the incident angle θ is the same, the diffraction angle is Therefore, it is not the same.

[0032] Taking specific parameters as an example, the sub-beam array 1 emits 5 laser sub-beams with central wavelengths λ of 1062.00nm, 1062.52nm, 1063.03nm, 1063.52nm, and 1064.00nm respectively. The spacing between adjacent sub-beams is 4mm, and all of them are incident on the diffraction grating 2 at an incident angle of θ=64°, causing diffraction. The grating line density is 1740 lines / mm. According to the grating diffraction equation Diffraction angle of each laser beam They are 71.64°, 71.80°, 71.97°, 72.13°, and 72.28° respectively.

[0033] The position of the moving return mirror 3 is calculated to be 503 mm away from the diffraction grating 2. The returned light beam converges on the diffraction grating 2, and each sub-beam is diffracted again and combined into one beam, which is emitted in the opposite direction parallel to the emission direction of the sub-beam array 1.

[0034] In the present invention, after the light trajectory of the sub-beam laser is folded back, the diffraction grating 2 is multiplexed twice, realizing a spectrum synthesis system with a simple structure, easy engineering implementation and compact size, avoiding the strict restrictions of the dual-grating spectrum synthesis system on the pitch azimuth parallelism and ultra-narrow sub-beam linewidth of the grating, and the single-grating spectrum synthesis system on the incident angle of each laser sub-beam; at the same time, by using the grating multiplexing method, the two diffractions can compensate for the angular dispersion caused by the grating, which is conducive to achieving higher spectrum synthesis beam quality.

[0035] The above merely describes the preferred embodiments of the present application, and it should be pointed out that, for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present application, and these improvements and modifications should also be considered as the protection scope of the present application.

Claims

1. A spectral synthesis system for grating multiplexing, characterized in that: include: A beamlet array (1), a diffraction grating (2) and a folding mirror (3) are provided. Each beamlet emitted by the beamlet array (1) is diffracted by the diffraction grating (2) and then emitted in the form of convergent light. After being reflected twice by a folding mirror (3), each laser beamlet is incident on the diffraction grating (2) again in the opposite direction parallel to the original light. By adjusting the distance between the folding mirror (3) and the diffraction grating (2), each beamlet is converged to a point on the diffraction grating (2). At this time, the incident angle of each beamlet is equal to the diffraction angle of the first diffraction from the diffraction grating (2), and the diffraction angle of each beamlet diffracted for the second time by the diffraction grating (2) is equal to the incident angle of the first diffraction, that is, the synthesized light beam is emitted in the opposite direction parallel to the light beam emitted from the beamlet array (1).

2. The spectral synthesis system for grating multiplexing according to claim 1, wherein: The beamlet dense array (1) is a fiber laser array composed of narrow linewidth laser beamlets with different central wavelengths arranged in one dimension.

3. The grating multiplexing spectrum synthesis system according to claim 2, wherein: The laser sub-beams of the sub-beam dense array (1) are emitted in parallel.

4. The grating multiplexing spectrum synthesis system according to claim 3, wherein: The diffraction grating (2) is a reflective grating.

5. The spectral synthesis system for grating multiplexing according to claim 3, wherein: The diffraction grating (2) is a transmission grating.

6. The grating multiplexing spectrum synthesis system according to claim 4 or 5, characterized in that: The folding mirror (3) is a single 90° folding mirror.

7. The grating multiplexing spectrum synthesis system according to claim 4 or 5, characterized in that: The folding mirror (3) is a combination of multiple separate reflecting mirrors.

8. The grating multiplexing spectrum synthesis system according to claim 4 or 5, characterized in that: According to the grating diffraction equation When the incident angle θ is the same, the central wavelength λ of each beamlet is different, and the diffraction angle Not the same either.

9. The grating multiplexing spectrum synthesis system according to claim 8, characterized in that: The sub-beam array (1) emits 5 laser sub-beams, with central wavelengths λ of 1062.00 nm, 1062.52 nm, 1063.03 nm, 1063.52 nm and 1064.00 nm respectively. The spacing between adjacent sub-beams is 4 mm, and all of them are incident on the diffraction grating (2) at an incident angle of θ=64°, causing diffraction. The grating line density is 1740 lines / mm.

10. The grating multiplexing spectrum synthesis system according to claim 9, characterized in that: According to the grating diffraction equation Diffraction angle of each laser beam They are 71.64°, 71.80°, 71.97°, 72.13°, and 72.28° respectively; the distance between the position of the movable return mirror (3) and the diffraction grating (2) is 503 mm.

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