Adaptive conversion of input beam with unsymmetrical intensity distribution to flattop beam based on dual SLMs

Abstract

We propose and demonstrate the adaptive conversion of input beam with unsymmetrical intensity distribution into a near-diffraction-limited flattop beam with desired parameters in the near field based on a combination of dual phase-only liquid crystal spatial light modulators (LC-SLMs) and the stochastic parallel gradient descent (SPGD) algorithm. One phase-only LC-SLM redistributes the intensity of the input beam to the desired distributions at the other phase-only LCSLM plane, and the other phase-only LC-SLM compensates the wavefront of the output beam. The SPGD algorithm adaptively optimizes the phase distributions of dual phase-only LC-SLMs to reduce the variance between the actual beam shape and the target beam shape. The experimental results on a prefabricated unsymmetrical input beam show that the technique is capable of adaptively creating near-diffraction-limited flattop beams with desired parameters.