Hearing carrier-envelope offset frequency and phase in air with a microphone

TL;DR

This paper demonstrates that a microphone can detect carrier-envelope offset frequency and phase in air by measuring laser-induced acoustic waves, offering a new method for ultrafast pulse characterization.

Contribution

It introduces a novel optoacoustic technique to measure CEP and pulse waveform directly using acoustic signals, bypassing traditional optoelectronic methods.

Findings

Acoustic signals depend on CEP in few-cycle pulses.

Laser-driven ionization causes amplitude modulation detectable acoustically.

Method enables direct optical pulse waveform characterization.

Abstract

Attosecond science and frequency metrology rely on the precise measurement and control of the laser pulse waveform, a feat traditionally achieved using optoelectronic techniques. In this study, we conducted a laser-induced acoustic experiment in air ionized by carrier-envelope phase (CEP)-stabilized sub-4 femtosecond pulses. Our results reveal that the acoustic signal exhibits CEP dependence in few-cycle pulses, primarily through amplitude modulation from laser-driven ionization. This novel optoacoustic phenomenon enables not only the measurement of the carrier-envelope offset frequency but also the direct characterization of the waveform of optical pulses through a microphone. Our study highlights the potential of laser-induced acoustic waves for advancing frequency metrology and ultrafast science.