Wavelength-tunable doughnut beam generation using few-mode long-period fiber grating

TL;DR

This paper demonstrates a broadband, wavelength-tunable method for generating optical doughnut beams using a long-period fiber grating combined with a tunable ytterbium-doped fiber laser, observing the vector nature of the beams.

Contribution

It introduces a novel approach to generate wavelength-tunable doughnut beams with ultra-broadband fiber gratings and fiber lasers, expanding spectral control and beam shaping capabilities.

Findings

Achieved ultra-broadband long-period fiber grating with 155 nm bandwidth.

Generated optical doughnut beams from 1030 nm to 1099 nm.

Observed the vector nature of the generated optical fields.

Abstract

Ultra-broadband long-period fiber grating with 10-dB bandwidth of 155 nm and 3-dB bandwidth of 415 nm is demonstrated around 1060 nm, which has been combined with a tunable ytterbium-doped fiber laser to generate optical doughnut beams in the spectral range from 1030 nm to 1099 nm, and the vector nature of generated optical fields are observed. The long-period fiber grating has also been used to transform the amplified spontaneous emission of an ytterbium-doped fiber amplifier into a broadband optical doughnut beam.