Post-compression of a Q-switched laser in a glass-rod multi-pass cell

TL;DR

This paper introduces a novel post-compression method using a multi-pass cell to shorten nanosecond Q-switched laser pulses to the picosecond regime, bridging the gap between traditional Q-switched and mode-locked lasers.

Contribution

The authors demonstrate a compact, effective post-compression scheme for Q-switched lasers using a glass-rod multi-pass cell, achieving pulse durations in the picosecond range.

Findings

Successfully compressed 0.5 ns pulses to 24 ps experimentally

Spectral broadening achieved with a compact glass-rod MPC

Numerical verification suggests compression to a few picoseconds is feasible

Abstract

Q-switched lasers are compact, cost-effective, and highly pulse energy-scalable sources for nanosecond-scale laser pulses. The technology has been developed for many decades and is widely used in scientific, industrial and medical applications. However, their inherently narrow bandwidth imposes a lower limit on pulse duration - typically in the few-hundred-picosecond range - limiting the applicability of Q-switched technology in fields that require ultrafast laser pulses in the few-picosecond or femtosecond regime. In contrast, mode-locked lasers can produce broad-band, ultrafast (< 1 ps) pulses, but are complex, expensive, and typically require a large footprint. To bridge the parameter gap between these two laser platforms - in terms of pulse duration and achievable peak power - we here propose a Herriott-type multi-pass cell (MPC) based post-compression scheme for shortening the pulse durations of Q-switched lasers down to the ultrafast, picosecond regime. We experimentally demonstrate post-compression of 0.5 ns, 1 mJ pulses from a Q-switched laser to 24 ps using a compact glass-rod MPC for spectral broadening. We verify this result numerically and show that compression down to a few picoseconds is possible using the nanosecond MPC (nMPC).