Spatio-temporal measurement of ionization-induced modal index changes in gas-filled PCF by prism-assisted side-coupling

TL;DR

This study uses prism-assisted side-coupling to explore the spatio-temporal evolution of ionization effects in gas-filled photonic crystal fibers, revealing gas dynamics and fiber vibrations over microsecond timescales.

Contribution

It introduces a novel experimental approach to measure ionization-induced index changes and gas dynamics in gas-filled fibers with high temporal and spatial resolution.

Findings

Gas density waves match hydrodynamic models.

Periodic fiber vibrations occur at MHz frequencies.

Ionization effects cause measurable index changes.

Abstract

We report the use of prism-assisted side-coupling to investigate the spatio-temporal dynamics of photoionization in an Ar-filled hollow-core photonic crystal fiber. By launching four different LP core modes we are able to probe temporal and spatial changes in the modal refractive index on timescales from a few hundred picoseconds to several hundred microseconds after the ionization event. We experimentally analyze the underlying gas density waves and find good agreement with quantitative and qualitative hydrodynamic predictions. Moreover, we observe periodic modulations in the MHz-range lasting for a few microseconds, indicating nanometer-scale vibrations of the fiber structure, driven by gas density waves.