Self-waveguiding of relativistic laser pulses in neutral gas channel

TL;DR

This paper demonstrates that ultrashort high-intensity laser pulses can self-generate plasma waveguides in neutral gas channels, enabling long-distance propagation and guiding subsequent pulses, with potential applications in laser physics.

Contribution

It introduces the concept of self-waveguiding of relativistic laser pulses in neutral gas channels and experimentally demonstrates this phenomenon over significant distances.

Findings

Self-waveguiding occurs over 10 cm or ~100 Rayleigh ranges.

Characteristic mode-beating oscillations are observed during propagation.

A fully ionized plasma waveguide is left behind for guiding subsequent pulses.

Abstract

We demonstrate that an ultrashort high intensity laser pulse can propagate for hundreds of Rayleigh ranges in a prepared neutral hydrogen channel by generating its own plasma waveguide as it propagates; the front of the pulse generates a waveguide that confines the rest of the pulse. A wide range of suitable initial index structures will support this "self-waveguiding" process; the necessary feature is that the gas density on axis is a minimum. Here, we demonstrate self-waveguiding of pulses of at least $1.5\times10^{17} W/cm^2$ (normalized vector potential $a_0\sim0.3)$ over 10 cm, or $\sim100$ Rayleigh ranges, limited only by our laser energy and length of our gas jet. We predict and observe characteristic oscillations corresponding to mode-beating during self-waveguiding. The self-waveguiding pulse leaves in its wake a fully ionized low density plasma waveguide which can guide another pulse injected immediately following; we demonstrate optical guiding of such a follow-on probe pulse