Supercontinuum generation in methane-filled hollow-core antiresonant fiber

TL;DR

This paper demonstrates broad, flat supercontinuum light generation from 350 nm to 1700 nm using methane-filled hollow-core antiresonant fiber pumped with 1030 nm pulses, highlighting the role of Raman effects and practical power scaling limits.

Contribution

It introduces a novel supercontinuum generation method in methane-filled fiber, showing enhanced spectral properties and analyzing the effects of gas pressure, fiber length, and pulse duration.

Findings

Achieved supercontinuum spanning 350-1700 nm with high flatness.

Raman scattering enhances supercontinuum compared to pure modulational instability.

Power scaling limited by fiber damage due to absorption.

Abstract

We report the generation of a multi-octave supercontinuum spanning from 350 nm to 1700 nm with exceptional spectral flatness and high conversion efficiency to both the visible and near infrared region, by pumping a methane-filled hollow-core antiresonant fiber with 1030 nm laser pulses. The dynamics exhibited signs of both modulational instability and stimulated Raman scattering. Fiber lengths ranging from 15 to 200~cm were investigated along with gas pressures up to 50 bar and pump pulse durations from 220~fs up to 10~ps. The best supercontinuum, in terms of spectral width and flatness, was achieved with 220~fs pulses, 25~bar filling pressure, and 60~cm propagation length. Comparison with argon-filled fiber with matched nonlinearity and dispersion showed that the Raman contribution enhances the supercontinuum generation process compared to a pure modulational instability-based process. The average power was scaled up by increasing the pulse repetition rate to 50~kHz, but further scaling was hindered by linear and nonlinear absorption leading to fiber damage.