Modulation-Slippage Tradeoff in Resonant Four-Wave Upconversion

TL;DR

This paper investigates four-wave mixing in underdense plasma for x-ray pulse amplification, revealing a tradeoff between modulation and slippage effects, and identifies optimal configurations for efficiency.

Contribution

It provides the first numerical simulations demonstrating seed amplification via four-wave mixing in plasma and explores strategies to mitigate limiting effects.

Findings

Parasitic effects limit amplification efficiency.

Dual seed approach is hindered by pulse slippage.

Single seed optimization yields best performance.

Abstract

Following up on a proposal to use four-wave mixing in an underdense plasma at mildly relativistic laser intensities to produce vastly more energetic x-ray pulses [V. M. Malkin and N. J. Fisch, Phys. Rev. E, 101, 023211 (2020)], we perform the first numerical simulations in one dimension to demonstrate amplification of a short high frequency seed through four-wave mixing. We find that parasitic processes including phase modulation and spatial pulse slippage limit the amplification efficiency. We numerically explore the previously proposed "dual seed" configuration as a countermeasure against phase modulation. We show how this approach tends to be thwarted by longitudinal slippage. In the examples we considered, the best performance was in fact achieved through optimization of signal and pump parameters in a "single seed" configuration.