Laser beam coherence and divergence angle complex controlling technique

Abstract

To reduce the complexity and cost of partially coherent optical system, increase the convenience of partially coherent laser beam application, in this paper, we presents a method to control the coherence and divergence angle of laser beam complexly, using a liquid crystal spatial light modulator (LC-SLM). First, we introduce the basic theory and method to control the coherence and divergence angle of laser beam complexly using an LC-SLM; then, we put forward the experiment to test the coherence and divergence angle controlling accuracy. The experiment results show that, for a partially coherent laser beam with the coherence and divergence angle of 0.9 mm, 7.5 mrad and 1.5 mm, 3.8 mrad, the error of coherence is less than 5%, the root-mean-square errors of the degree of coherence are 0.027 386 and 0.031 314, and the peak-to-valley values are 0.084 658 and 0.089 103 respectively; the error of divergence angle is less than 5%, the root-mean-square errors of the divergence angle are 0.022 478 and 0.023 186, and the peak-to-valley values are 0.081 201 and 0.092 130 respectively. This method can control degree of coherence and divergence angle with high accuracy.