Quadriwave lateral shearing interferometry (QWLSI) could acquire the phase and intensity distribution of laser beam with remarkable resolution in only one measurement. It’s a potential method to measure the phase step of multimode laser. However, the discontinuity point of intensity will reduce the quality of interferogram and lead to wrong wavefront retrieve result. In this paper, analysis and simulations have been conducted on the measuring ability of the QWLSI for the higher-order modes (HOM) in large mode area (LMA) fiber. A set of interferogram image of ideal linearly polarized (LP) mode are calculated and analyzed by a commercial retrieve software. The results show that the proper ratio of the shearing distance to the gap size between HOM petals is the critical parameter to retrieve wavefront correctly. To study the influence of coherence on wavefront retrieving, we calculated the interferogram of multimode laser with different modal phase fluctuation. The results indicate that the partially coherent beam will introduce significant ambiguity into the retrieved wavefront. Finally, the feasibility of wavefront correction of multimode laser with LSI and spatial light modulator is demonstrated with simulations.
Kun Xie, Wenguang Liu, Qiong Zhou, Hongmiao Zhao, and Xiaojun Xu, "Numerical study of the measurement capability of quadriwave lateral shearing interferometry for multimode fiber laser (Conference Presentation)," Proc. SPIE 10436, High-Power Lasers: Technology and Systems, Platforms, and Effects, 104360A (Presented at SPIE Security + Defence: September 14, 2017; Published: 26 October 2017); https://doi.org/10.1117/12.2277995.5626166863001.
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