Acoustic measurement for the determination of ultrashort pulse duration

An entirely optics-free technique for pulse duration estimation and monitoring is proposed. The approach relies on the generation and monitoring of an acoustic signal resulting from the air breakdown induced by focused ultrashort laser pulses. The experimentally determined dependence of the acoustic signal amplitude on pulse energy and duration is in accordance with the plasma physics of air breakdown. The proposed technique offers simplicity of implementation, compatibility with laser radiation of all spectral ranges, and suitability for in-situ monitoring of pulse duration and energy fluctuations in laser materials processing.