A mode generator and multiplexer at visible wavelength based on all‐fiber mode selective coupler
Han Yao, Fan Shi, Zhaoyang Wu, Xinzhu Xu, Teng Wang, Xiaomin Liu, Peng Xi, Fufei Pang, Xianglong Zeng
Abstract
Abstract Using an all‐fiber mode selective coupler (MSC) at the visible band, here we experimentally demonstrate a generating and wavelength multiplexing scheme for the cylindrical vector (CV) and vortex beams (VBs). The proposed MSCs act as efficient mode converters to produce spectrally insensitive high‐order modes (HOMs) at the wavelength ranging from 450 to 980 nm, which have broad operation bandwidth (more than 7 nm), high mode conversion efficiency (94%), and purity (98%), and low insert loss (below 0.5 dB). By adjusting the polarization state and the phase shift of linear polarization (LP) 11 mode respectively, the donut‐shaped CVs and circular‐polarization VBs are achieved. The focused intensity distribution of the donut beam on the cross‐ and axial‐sections is monitored by using a confocal system. The all‐fiber solution of producing and multiplexing HOMs opens a new route for stimulated emission depletion microscopy applications.