Self-compression of stimulated Raman backscattering by flying focus

TL;DR

This paper introduces a new plasma-based backward Raman amplification regime using a flying focus, enabling direct pulse compression and simplifying the setup by eliminating the need for seed synchronization.

Contribution

It proposes a novel self-compression regime for BRA with flying focus, supported by 2D PIC simulations showing significant pulse compression without seed synchronization.

Findings

Pump pulse compressed from 26ps to 116fs

Output amplitude comparable to synchronized short seed

Simplifies Raman amplifiers and reduces jitter issues

Abstract

A novel regime of self-compression is proposed for plasma-based backward Raman amplification(BRA) upon flying focus. By using a pumping focus moving with a speed equal to the group velocity of stimulated Raman backscattering(SRBS), only a short part of SRBS which does always synchronize with the flying focus can be amplified. Due to the asymmetrical amplification, the pulse can be directly compressed in the linear stage of BRA. Therefore, instead of a short pulse, the Raman spontaneous or a long pulse can seed the BRA amplifiers. The regime is supported by the 2D particle-in-cell(PIC) simulation without a seed, presenting that the pump pulse is compressed from 26ps to 116fs, with an output amplitude comparable with the case of a well-synchronized short seed. This method provides a significant way to simplify the Raman amplifiers and overcome the issue of synchronization jitter between the pump and the seed.