Double-Pass Multipass Cell Compressor for Peak Power Enhancement of μJ Pulse Energies

Temporal pulse compression of Yb-based laser systems via multipass cell (MPC) compression continues to be a highly active research area, enabling high-efficiency temporal pulse compression at very high average powers in a wide variety of parameter windows [1]. MPCs based on bulk material are the most simple and attractive approach for <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mu \mathrm{J}$</tex> pulse energies but face challenges in achieving high compression ratios and peak power due to complex pulse propagation dynamics, often requiring multiple stages for boosting peak power enhancement. Fritsch et al. demonstrated pulse compression from 220 fs down to 18 fs at an input pulse energy of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$3.5 \mu \mathrm{J}$</tex>, by implementing three bulk-based MPC stages with 60% transmission [2]. In 2020, Vicentini et al. compressed <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$15.6-\mu \mathrm{J}$</tex> pulses from 460 fs to 22 fs using two compression stages with 76% transmission [3]. In this work, we demonstrate a simpler implementation for bulk nonlinear pulse compression with large compression ratios, using a double propagation scheme in a single-stage MPC, with an intermediate partial compression between two passes. We optimize and use this concept to compress a 100W-average-power class oscillator, achieving high peak power enhancement by a factor of 9.5 and a temporal compression ratio of 15, which could so far only be achieved with multi-stage compressors. The peak power of the oscillator is thus increased from 13 MW to 125 MW.