| Fiber laser has excellent performance and a wide application prospect.However,with the increase of output power,the degradation of beam quality caused by the nonlinear effect and other factors seriously restricts the use of fiber lasers.The multi-mode fiber laser has less restriction on structure and other factors and can withstand higher power output,while the output brightness is affected by the poor quality of the multi-mode beam.Therefore,the structure of the output mode of multi-mode fiber laser has grown up to be a hot spot.The measurement of multi-transverse mode optical field is the basis of multi-transverse mode beam control.In this paper,a multi-transverse mode beam coherence measurement method based on liquid crystal spatial light modulator is proposed,which can provide important data support for mode decomposition of high-power fiber lasers,and is of great reference value for beam control of high-power fiber lasers.Firstly,the physical properties of multi-mode beams are analyzed based on partially coherent light theory,and the related physical quantity to measure coherence are analyzed,which provides the theoretical basis for the subsequent multi-transverse mode optical field coherence measurement.Based on the liquid crystal spatial light modulator,a method for measuring the coherence distribution of multi-transverse mode optical field is proposed,and the verification experiment was conducted.Secondly,a multi-transverse mode optical field coherence measurement system based on liquid crystal spatial light modulator is constructed.The measurement of beam coherence is studied theoretically and experimentally.In this paper,the optical field coherence distribution of 635 nm single / multimode fiber laser and 1064 nm single / multimode fiber laser can be measured rapidly and accurately by using the liquid crystal spatial light modulator,which verifies the correctness of the method and measurement system. |
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