Picosecond ultrasonics with a free-running dual-comb laser

TL;DR

This paper introduces a high-power, free-running dual-comb laser system for picosecond ultrasonic measurements, demonstrating its effectiveness and advantages over traditional locked-laser setups in non-destructive testing.

Contribution

The work presents the first application of a free-running dual-comb laser for picosecond ultrasonics, simplifying the setup and reducing costs compared to locked-laser systems.

Findings

Successfully measured ultrasonic signatures in semiconductor structures.

Demonstrated comparable results to locked femtosecond laser systems.

Showed potential for cost-effective non-destructive testing.

Abstract

We present a free-running 80-MHz dual-comb polarization-multiplexed solid-state laser which delivers 1.8 W of average power with 110-fs pulse duration per comb. With a high-sensitivity pump-probe setup, we apply this free-running dual-comb laser to picosecond ultrasonic measurements. The ultrasonic signatures in a semiconductor multi-quantum-well structure originating from the quantum wells and superlattice regions are revealed and discussed. We further demonstrate ultrasonic measurements on a thin-film metalized sample and compare these measurements to ones obtained with a pair of locked femtosecond lasers. Our data show that a free-running dual-comb laser is well-suited for picosecond ultrasonic measurements and thus it offers a significant reduction in complexity and cost for this widely adopted non-destructive testing technique.