CN-120999391-B - Large-array scale polarization spectrum hybrid synthesis optical system

CN120999391BCN 120999391 BCN120999391 BCN 120999391BCN-120999391-B

Abstract

A large-array scale polarization spectrum hybrid synthesis optical system comprises (1) a polarization synthesis module based on a reflection type polarization beam combining grating, which is used for improving the output power of single sub-beam laser and providing high-power and high-beam quality sub-beam incident light for a subsequent system module, and (2) a spectrum synthesis module which is used for combining multi-wavelength unpolarized or single sub-beam laser to obtain higher-power synthesis laser output. The synthetic optical system is based on the reflective all-medium polarization beam combining grating and the spectral beam combining grating, adopts a mixed synthesis technology combining polarization beam combining and spectral beam combining, and can greatly increase the laser output power and keep the whole beam quality unchanged, thereby realizing the output of the laser system with high power, high beam quality and high synthesis efficiency.

Inventors

CAO HONGCHAO
CAI YALIN
JIN YUNXIA
WANG RUI
ZHANG YIBIN
WANG YUNKUN
HAN YUXING
KONG FANYU

Assignees

中国科学院上海光学精密机械研究所

Dates

Publication Date: 20260512
Application Date: 20250728

Claims (5)

1. A large-array-scale polarization spectrum hybrid synthesis optical system, comprising, in order along a beam transmission direction: the polarization synthesis module is used for receiving the multi-beam laser and carrying out polarization beam combination treatment to output linearly polarized light or unpolarized light; The spectrum synthesis module is connected with the light path of the polarization synthesis module, selects different beam combination modes according to the polarization characteristics of the output light of the polarization synthesis module, and performs spectrum beam combination on the multi-wavelength laser; The polarization synthesis module consists of a plurality of S-polarization sub-beam lasers, P-polarization sub-beam lasers, a reflective polarization beam combining grating and a polarization conversion module, wherein S-polarization light emitted by the S-polarization sub-beam lasers and P-polarization light emitted by the P-polarization sub-beam lasers are modulated into the polarization state of the beam laser through the reflective polarization beam combining grating; two modes of operation of the spectral synthesis module: When the sub-beam laser output by the polarization synthesis module is unpolarized, adopting a reflection type polarization independent beam combination grating and a reflecting mirror to form a structure; when the sub-beam laser output by the polarization synthesis module is linearly polarized light, adopting a cascade structure of a double-grating spectrum beam combining system I, a polarization conversion module, a plane mirror and a double-grating spectrum beam combining system II; The double-grating spectrum beam combining system I comprises a first grating and a second grating which are arranged in parallel, and is used for receiving the multi-wavelength S polarized light from the polarization combining module for dispersion compensation so as to realize high diffraction efficiency and high beam quality beam combination of the multi-wavelength incident S light and outputting the combined S polarized light to the polarization conversion module; the polarization conversion module is used for converting the S polarized light after beam combination into P polarized light; the plane reflector is used for reflecting and adjusting the angle of incidence of the P polarized light to the double-grating spectrum beam combining system II so as to realize high-efficiency beam combining of a subsequent system; The double-grating spectrum beam combining system II adopts a spectrum beam combining grating and a broadband polarization beam combining grating which are arranged in parallel, wherein, The spectrum beam combining grating receives S polarized light with different wavelengths output from different polarization combining modules, diffracts and combines the S polarized light into S polarized light which is diffracted and emergent at a 1-level, the broadband polarization beam combining grating receives P polarized light output by the double-grating spectrum beam combining system I, and the P polarized light is reflected at a 0-level of the broadband polarization beam combining grating and then combines the P polarized light with the S polarized light which is diffracted and emergent at the 1-level into a high-power laser, so that high-efficiency beam combining of the S light at the 1-level and the P light at the 0-level is realized.
2. The large-array-scale polarization spectrum hybrid synthesis optical system according to claim 1, wherein the polarization synthesis module operates in a manner comprising: the working mode one is that by locking the phase difference of the S polarized sub-beam laser and the P polarized sub-beam laser, linear polarized light is output, and a plurality of polarization beam combining gratings are used and matched with a polarization conversion module, so that large-scale combined beams can be realized; and in the second working mode, when the phase difference of the S-polarization sub-beam laser and the P-polarization sub-beam laser is not locked, unpolarized light is output.
3. The large-array-scale polarization spectrum hybrid synthesis optical system according to claim 1, wherein the grating in the dual-grating spectrum beam-combining system II has the same reticle density, and the grating belongs to a wide-spectrum polarization beam-combining grating, has-1-level diffraction efficiency for broad-spectrum laser incident with S polarization, and has 0-level reflectivity for broad-spectrum laser incident with P polarization.
4. The large-scale polarization spectrum hybrid synthesis optical system according to claim 1, wherein the polarization beam-combining grating is composed of a grating etching layer, a phase matching layer, a periodic film system and a grating substrate, which are sequentially arranged from top to bottom, wherein the periodic film system is composed of a high refractive index material layer and a low refractive index material layer which are laminated, the grating substrate material and the periodic film system form a bottom high reflection layer, the film system of the bottom high reflection layer is S (H2L) m H, wherein S is a low expansion and high thermal conductivity grating substrate, and H and L respectively represent optical thicknesses of A high refractive index material layer and a low refractive index material layer, The phase matching layer is formed by laminating an upper high refractive index material layer and a lower low refractive index material layer, the top grating etching layer with a trapezoid groove-shaped section is formed by a lower high refractive index material sub-grating layer and an upper low refractive index material top grating layer, when the grating is used in 1030-1080 nanometer wave band, the linear density of the grating is 1100-1500 lines/millimeter, the etching depth (h 1 +h 2 ) is 445.7-453.4 nanometers, and the inclination angle between the grating side wall and the grating vector direction is between At 80 deg., w is the width of the top of the grating, the width ratio w/lambda of the top of the grating is 0.1-0.2.
5. The large-array-scale polarization spectrum hybrid synthesis optical system according to claim 1, wherein the grating etching layer of the polarization beam combining grating, the phase matching layer and the periodic film system are made of SiO 2 , the grating etching layer and the phase matching layer are made of HfO 2 , and the periodic film system is made of Ta 2 O 5 .

Description

Large-array scale polarization spectrum hybrid synthesis optical system Technical Field The invention relates to the technical field of high-energy laser beam combining, in particular to a large-array-scale polarization spectrum hybrid synthesis optical system. Background The high-power laser system has great application value in the fields of leading-edge basic scientific research, intelligent manufacturing and the like. The high power density of single laser can cause optical damage to fiber core and end face, thermal effect and nonlinear effect of laser, which severely limits the output power and beam quality of fiber laser, so that the technology of synthesizing multiple laser beams to improve power output, called beam combination for short, has been developed. Therefore, in order to improve the output power of the laser, at present, methods such as spatial beam combination, polarization beam combination, wavelength beam combination and the like are mainly adopted at home and abroad to couple a plurality of lasers into a beam of laser for direct output or coupling output by an optical fiber. The diffraction grating-based Spectral Beam Combining (SBC) technology has the advantages of good beam quality and relatively simple structure, and is outstanding in a plurality of beam combining technologies. The spectrum beam combination diffracts laser with different wavelengths to the same direction to be emitted by using a diffraction element represented by a grating, thereby providing a technical path for realizing high-power and high-beam quality combined output. The combination technology of combining polarization beam combination and spectrum beam combination is expected to greatly improve the array scale and output power of the combined laser. At present, a polarization beam splitter (Polarization beam splitter, PBS) is mainly adopted to realize the beam combination of polarized light, but the PBS has a transmission beam, so the thermal damage and the multi-interface Fresnel reflection of the PBS under the action of high-power laser limit the power loading capacity and the combination efficiency. In contrast, the reflective polarization beam-combining grating based on the multilayer dielectric film has higher laser damage resistance and higher synthesis efficiency because of the absence of high-energy transmitted light beams. The polarization beam combination can improve the polarization characteristic of the laser, the spectrum beam combination can optimize the spectrum characteristic of the laser, and the combination of the polarization beam combination and the spectrum beam combination can further improve the beam quality of the combined laser. And the combination technology can reduce the dependence on a single beam combination technology and improve the reliability and stability of the system. Therefore, the combination technology of polarization beam combination and spectrum beam combination is an effective way for breaking through the bottleneck of the prior art and realizing the large-scale improvement of the beam combination laser array and the large-scale improvement of the output power. With the continuous development and perfection of the related technology, the combined technology plays an increasingly important role in the future laser technology field. Disclosure of Invention The invention aims to solve the problems of limited power improvement, reduced beam quality, low synthesis efficiency and the like in the existing laser beam combining technology, and provides a large-array-scale polarization spectrum hybrid synthesis optical system which performs multiple high-diffraction efficiency beam combining on incident linearly polarized light/unpolarized light through the synergistic effect of a polarization synthesis module and a spectrum synthesis module, so that the overall beam quality is kept unchanged while the laser module is greatly increased (namely, the output power is increased), and high-quality beam combining output is realized. The technical scheme of the invention is as follows: a large-array-scale polarization spectrum hybrid synthetic optical system, comprising: The polarization synthesis module consists of a plurality of S-polarization sub-beam lasers, P-polarization sub-beam lasers, a reflective polarization beam combining grating and a polarization conversion module, and is used for providing high-power and high-quality linearly polarized light or unpolarized light and providing high-power sub-beam lasers with different wavelengths and different polarization states for subsequent system modules; the spectrum synthesis module has two working modes according to different polarization characteristics of the sub-beam laser output by the polarization synthesis module: The mode 1 is that when the sub-beam laser output by the polarization synthesis module is unpolarized, the spectrum synthesis module consists of a reflection type polarization independent beam combining grating and