# Pulse contrast enhancement via non-collinear sum-frequency generation with the signal and idler of an optical parametric amplifier

## TL;DR

This paper presents a technique using non-collinear sum-frequency generation to enhance the temporal contrast of high-intensity laser pulses by over 8 orders of magnitude, improving pulse quality for advanced laser systems.

## Contribution

It introduces a novel, energy-scalable method for temporal contrast enhancement using non-collinear sum-frequency generation with the signal and idler of an optical parametric amplifier.

## Key findings

- Achieved >10^12 contrast relative to pre-pulses and ASE >5 ps prior to main pulse
- Maintained percent-level energy stability during operation
- Produced 1 J, 40 fs laser pulses with >10^10 contrast >30 ps before main pulse

## Abstract

We outline an approach for improving the temporal contrast of a high-intensity laser system by $>$8 orders of magnitude using non-collinear sum-frequency generation with the signal and idler of an optical parametric amplifier. We demonstrate the effectiveness of this technique by cleaning pulses from a millijoule-level chirped-pulse amplification system to provide $>$10$^{12}$ intensity contrast relative to all pre-pulses and amplified spontaneous emission $>$5~ps prior to the main pulse. The output maintains percent-level energy stability on the time scales of a typical user experiment at our facility, highlighting the method's reliability and operational efficiency. After temporal cleansing, the pulses are stretched in time before seeding two multi-pass, Ti:sapphire-based amplifiers. After re-compression, the 1~J, 40~fs (25~TW) laser pulses maintain a $>$10$^{10}$ intensity contrast $>$30~ps prior to the main pulse. This technique is both energy-scalable and appropriate for preparing seed pulses for a TW- or PW-level chirped-pulse amplification laser system.