title: Adaptive conversion of multimode beam to near-diffraction-limited flattop beam based on dual-phase-only liquid-crystal spatial light modulators.
abstract: We propose and demonstrate the adaptive conversion of a multimode beam into a near-diffraction-limited flattop beam 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 multimode beam, and the other 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 fiber multimode beam show that the system is capable of adaptively creating square and rectangle flattop beams with desired parameters. Beam quality can be greatly improved by this system. The power in the main lobe of the far-field spot is about 4 times larger than that of the input multimode beam.
authors.affiliation: College of Photon-Electron Science and Engineering, National University of Defense Technology, Changsha, Hunan, China.
authors.forename: Haotong
authors.initials: H
authors.lastname: Ma
authors.forename: Haichuan
authors.initials: H
authors.lastname: Zhao
authors.forename: Pu
authors.initials: P
authors.lastname: Zhou
authors.forename: Xiaolin
authors.initials: X
authors.lastname: Wang
authors.forename: Yanxing
authors.initials: Y
authors.lastname: Ma
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Xu
authors.forename: Zejin
authors.initials: Z
authors.lastname: Liu
mesh_terms: D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005336:Fiber Optic Technology / Q000295:instrumentation*; D008027:Light; D050866:Liquid Crystals / Q000737:chemistry*; D012031:Refractometry / Q000295:instrumentation*; D012542:Scattering, Radiation