Coherent subcycle optical shock from superluminal plasma wake

TL;DR

This paper introduces a novel method to generate coherent subcycle optical pulses using relativistic electron beams in plasma with a density gradient, producing highly directional, tunable, and ultra-short radiation.

Contribution

It presents a new mechanism for subcycle pulse generation via superluminal plasma wake, combining simulations and analytical models to demonstrate its effectiveness.

Findings

Produced isolated subcycle optical shocks at the Cherenkov angle.

Achieved ultra-short attosecond-scale pulses with high intensity.

Demonstrated tunability of the central frequency across a wide spectrum.

Abstract

We propose a new mechanism for generating coherent subcycle optical pulse by directing a relativistic electron beam (REB) into a plasma with a density up-ramp. The subcycle pulse is coherently emitted by bubble-sheath electrons in REB-induced superluminal plasma wake. Using three-dimensional particle-in-cell and far-field time-domain radiation simulations as well as analytical modeling, we show that an isolated subcycle optical shock can be produced at the Cherenkov angle. This radiation has ultra-short attosecond-scale duration and high intensity and exhibits excellent directionality with ultra-low angular divergence and stable carrier envelope phase. Its central frequency can be easily tuned over a wide range, from the far-infrared to the ultra-violet, by adjusting the plasma and driver-beam density.