Temporal characterization of laser pulses using an air-based knife-edge technique

TL;DR

This paper demonstrates a simple, reliable method for ultrashort laser pulse characterization in ambient air using plasma-induced optical switching, enabling detailed temporal and spectral analysis without extra optical components.

Contribution

The study extends the PI-FROSt technique from rare gases to ambient air, simplifying implementation and maintaining high accuracy in pulse characterization.

Findings

Effective pulse reconstruction in ambient air

No additional optical components needed

Comparable performance to gas-based methods

Abstract

We present the characterization of ultrashort laser pulses by using the plasma-induced frequency resolved optical switching (PI-FROSt) technique, implemented in ambient air. This recently developed method allows for a temporal reconstruction of a pulse at its focal spot by utilizing a moderately intense pump laser pulse for generating an ionization-induced ultrafast defocusing lens. When propagating through the produced plasma lens, the probe beam to characterize experiences an increase of its size in the far field. The spectrum of the defocused probe field, measured as a function of the pump-probe delay, allows for a comprehensive characterization of the temporal and spectral attributes of the pulse. We report herein the ability of this technique, initially designed for use in rare gases, to operate in ambient air conditions with similar performance. The method is remarkably straightforward to implement and requires no additional optical component other than a focusing mirror, while delivering laser pulse reconstructions of high reliability.