Resonant dispersive wave emission in hollow capillary fibres filled with pressure gradients

TL;DR

This paper explores how a pressure gradient in hollow capillary fibres influences resonant dispersive wave emission, enabling efficient, short-duration ultraviolet pulses for ultrafast science applications.

Contribution

It introduces a simple scaling rule for gas pressure in pressure-gradient fibres and demonstrates the generation of transform-limited 3 fs pulses.

Findings

Pressure gradients enable dispersion-free pulse delivery.

Short waveguides produce 3 fs transform-limited pulses.

Pressure gradients influence the dispersive wave spectrum.

Abstract

Resonant dispersive wave (RDW) emission in gas-filled hollow waveguides is a powerful technique for the generation of bright few-femtosecond laser pulses from the vacuum ultraviolet to the near infrared. Here we investigate deep-ultraviolet RDW emission in a hollow capillary fibre filled with a longitudinal gas pressure gradient. We obtain broadly similar emission to the constant-pressure case by applying a surprisingly simple scaling rule for the gas pressure and study the energy-dependent dispersive-wave spectrum in detail using simulations. We further find that in addition to enabling dispersion-free delivery to experimental targets, a decreasing gradient also reduces the pulse stretching within the waveguide itself, and that transform-limited pulses with 3 fs duration can be generated by using short waveguides. Our results illuminate the fundamental dynamics underlying this frequency conversion technique and will aid in fully exploiting it for applications in ultrafast science and beyond.