title: Near-diffraction-limited flattop laser beam adaptively generated by stochastic parallel gradient descent algorithm.
abstract: We demonstrate the adaptive generation of a near-diffraction-limited flattop laser beam in the near field based on the stochastic parallel gradient descent algorithm and dual-phase-only liquid crystal spatial light modulators (LC-SLMs). One LC-SLM redistributes the intensity, and the other compensates the wavefront of the output beam. The experimental results show that approximately 69% of the power is enclosed in a region with less than 6% rms intensity variation. The 5mm diameter near-diffraction-limited output beam retains a flattop intensity distribution without significant diffraction peaks for a working distance of more than 30 cm.
authors.affiliation: College of Photon-electron Science and Engineering, National University of Defense Technology, Changsha, Hunan, 410073, China.
authors.forename: Haotong
authors.initials: H
authors.lastname: Ma
authors.forename: Zejin
authors.initials: Z
authors.lastname: Liu
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Xu
authors.forename: Sanhong
authors.initials: S
authors.lastname: Wang
authors.forename: Changhai
authors.initials: C
authors.lastname: Liu