Adaptive control of waveguide modes in a two-mode-fiber

Abstract

We experimentally demonstrate an adaptive-optics-based approach that allows selective excitation of waveguide modes and their mixtures in a two-mode fiber (TMF). A phase-only spatial light modulator is used for wavefront control, using feedback signals provided by the correlation between the experimentally measured field distribution and the desired mode profiles. Experimental results show the optical field within the TMF can be shaped to be pure linearly polarized (LP) modes or their combinations. Analysis shows selective mode excitation can be achieved using only 5 × 5 independent phase blocks. With proper feedback signals, this method should enable one to precisely control the optical field within any multimode fiber or other types of waveguides in real time.

Wavefront shaping for optimized many-mode Kerr beam self-cleaning in graded-index multimode fiber

“…Its mechanical orientation as well as the position of the lens for injection in the MMF were finely tuned to obtain efficient coupling into the fiber, and to observe self-cleaning on the fundamental mode, as the launched beam power was progressively raised. Optimization of the input wavefront was based on the intensity correlation between the experimental output image Iexp and the target output mode pattern Itar, in a way to minimize the cost function [22]…”

Hundred-watt level high-order mode all-fiberized random distributed feedback Raman fiber laser with high mode purity

“…Fiber lasers with effective modal control to achieve specific highorder modes (HOMs) output have attracted much attention in the past few decades, thanks to their unique polarization, amplitude, and phase characteristics, which have been applied to mode division multiplexing [1] , industrial processing [2] , and so on. Moreover, further generation of cylindrical vector beams and vortex beams based on HOMs has also been verified [3][4][5][6][7][8][9] , which finds a tremendous range of applications, including plasmon excitation [10] , optical tweezers [11] , and electron acceleration [12] .…”

All-Fiber Laser With Agile Mode-Switching Capability Through Intra-Cavity Conversion

“…Fiber lasers with pure high-order-mode (HOM) output have been intensively studied in recent years owing to their unique polarization, amplitude and phase characteristics. Generally, there are several commonly used approaches to realize HOM operation, including adopting spatial light modulators [1], [2], employing long period gratings [3], [4], introducing adaptive control [5]- [7], using few-mode fiber Bragg gratings (FBGs) [8]- [10] and taking advantage of mode selective couplers [11], [12]. Currently, exploration on HOM fiber lasers has focused on power scaling [13], nonlinear conversion [4], [14], vector beam generation [15], etc.…”