Spectral broadening in convex-concave multipass cells

TL;DR

This paper introduces a novel convex-concave multi-pass cell design that enhances spectral broadening capabilities, enabling higher energy pulses with improved homogeneity and efficiency, overcoming previous limitations like damage and ionization.

Contribution

The paper presents a new convex-concave multi-pass cell configuration that significantly improves spectral broadening performance and energy scaling in ultrafast pulse generation.

Findings

Achieved spectral broadening of 260 fs pulses to ~50 fs with 90% efficiency.

Demonstrated high spatio-spectral homogeneity across the beam profile.

Showcased potential for energy scaling beyond previous limitations.

Abstract

Since its first demonstration in 2016, the multi-pass spectral broadening technique has covered impressive ranges of pulse energy (3 $\mu$J - 100 mJ) and peak power (4 MW - 100 GW). Energy scaling of this technique into the joule-level is currently limited by phenomena such as optical damage, gas ionization and spatio-spectral beam inhomogeneity. These limitations can be overcome by the novel multi-pass convex-concave arrangement, which exhibits crucial properties such as large mode size and compactness. In a proof-of-principle experiment, 260 fs, 15 $\mu$J and 200 $\mu$J pulses are broadened and subsequently compressed to approximately 50 fs with 90 % efficiency and excellent spatio-spectral homogeneity across the beam profile.