Vector mode conversion based on an asymmetric fiber Bragg grating in few-mode fibers

Abstract

We propose a vector mode conversion approach based on asymmetric fiber Bragg gratings (AFBGs) written in step-index fiber and vortex fiber, respectively. The mode coupling properties of AFBGs are numerically investigated. Compared to step-index fiber, the large mode separation in the vortex fiber is beneficial to extracting the desired vector mode at specific wavelengths. In addition, the polarization of incident light and the attenuation coefficient of index change distribution of the AFBG play critical roles in the mode coupling process. The proposed AFBG provides an efficient method to realize high-order vector mode conversion, and it shows great potential for orbital angular momentum multiplexing and fiber lasers with vortex beam output.

Recent progress of dynamic mode manipulation via acousto-optic interactions in few-mode fiber lasers: mechanism, device and applications

“…Dynamic mode manipulation should be considered during generating spatial high-order modes (HOMs) directly, which can greatly improve the practical utilities of these light sources. Static methods of generating spatial modes in optical fibers can be mainly classified into four categories: mode selective couplers (MSCs) [29][30][31], photonic lanterns [32][33][34], long-period gratings (LPGs) [35][36][37][38] and fiber Bragg gratings (FBGs) [39][40][41]. MSC employs tapering fused fibers to demonstrate mode coupling via evanescent field interactions.…”

On-line Writing of Fiber Bragg Grating Array on a Two-mode Optical Fiber for Sensing Applications

“…It has been demonstrated that pressure, stress and curvature sensing can be realized individually using a few-mode fiber based sensing system [8,9,10,11]. If now we consider combining it with the FBG technology, a few-mode FBG, therefore, it can be expected to be used for multi-parameter measurements and comparatively reduced cross-sensitivity, as observed in single-mode FBG [12,13,14,15].…”