Generation of femtosecond optical vortex beams in all-fiber mode-locked fiber laser using mode selective coupler

TL;DR

This paper reports the first experimental demonstration of a mode-locked fiber laser producing high-order femtosecond optical vortex beams using a mode selective fused coupler, enabling broadband conversion and direct vortex pulse output.

Contribution

It introduces a novel all-fiber mode-locked laser setup with a fused coupler for high-order vortex pulse generation, expanding capabilities in fiber laser beam shaping.

Findings

Generated 140 fs vortex pulses with 67 nm spectral width

Broadband mode conversion over 100 nm

First demonstration of high-order vortex pulses in mode-locked fiber laser

Abstract

We experimentally demonstrated a high-order optical vortex pulsed laser based on a mode selective all-fiber fused coupler composed of a single-mode fiber (SMF) and a few-mode fiber (FMF). The fused SMF-FMF coupler inserted in the cavity not only acts as mode converter from LP01 mode to LP11 or LP21 modes with a broadband width over 100 nm, but also directly delivers femtosecond vortex pulses out of the mode locked cavity. To the best of our knowledge, this is the first report on the generation of high-order pulse vortex beams in mode-locked fiber laser. The generated 140 femtosecond vortex beam has a spectral width of 67 nm centered at 1544 nm.