Multiple soliton compression stages from competing plasma nonlinearities in mid-IR gas-filled hollow-core fibers

TL;DR

This paper numerically studies how competing plasma nonlinearities in mid-IR gas-filled hollow-core fibers lead to multiple soliton self-compression stages and supercontinuum generation, enabling potential ultrafast pulse sequences.

Contribution

It reveals the mechanism of multiple soliton compression stages caused by competing nonlinearities, with implications for ultrafast pulse generation.

Findings

Multiple soliton self-compression stages observed.

Supercontinuum spanning 1-4 μm generated.

Plasma nonlinearities can be tuned to control soliton dynamics.

Abstract

We investigate numerically soliton-plasma interaction in a noble-gas-filled silica hollow-core anti-resonant fiber pumped in the mid-IR at 3.0 {\mu}m. We observe multiple soliton self-compression stages due to distinct stages where either the self-focusing or the self-defocusing nonlinearity dominates. Specifically, the parameters may be tuned so the competing plasma self-defocusing nonlinearity only dominates over the Kerr self-focusing nonlinearity around the soliton self-compression stage, where the increasing peak intensity on the leading pulse edge initiates a competing self-defocusing plasma nonlinearity acting nonlocally on the trailing edge, effectively preventing soliton-formation there. As the plasma switches off after the self-compression stage, self-focusing dominates again, initiating another soliton self-compression stage in the trailing edge. This process is accompanied by supercontinuum generation spanning 1-4 {\mu}m. The technique could be exploited to generate an ultrafast sequence of several few-cycle pulses.