# Spatio-temporal pulse cleaning in multi-pass cells

## TL;DR

This paper investigates nonlinear temporal filtering techniques, NER and XPW, for improving the contrast and quality of high-energy femtosecond laser pulses in a multi-pass cell, achieving significant contrast enhancement and high efficiency.

## Contribution

It introduces the application of NER and XPW techniques for spatio-temporal cleaning of high-energy laser pulses within a multi-pass cell, demonstrating record efficiencies and contrast improvements.

## Key findings

- Contrast enhancement > 3 orders of magnitude
- High conversion efficiencies achieved
- Effective control of pulse duration through nonlinearity and dispersion balancing

## Abstract

We study both numerically and experimentally the use of two third-order nonlinear temporal filtering techniques, namely nonlinear ellipse rotation (NER) and cross-polarized wave (XPW) generation, for spatio-temporal cleaning of mJ energy 30 fs Titanium:Sapphire laser pulses in a multi-pass cell. In both cases, a contrast enhancement greater than 3 orders of magnitude is observed, together with excellent output pulse quality and record high conversion efficiencies. Careful balancing of nonlinearity and dispersion inside the multi-pass cell helps tune the spectral broadening process and control the post-compressed pulse duration for specific applications.