Temporal Characterization of Laser Pulses Using an Air-Based Knife-Edge Technique

The characterization of ultrashort laser pulses is presented by using the plasma-induced frequency-resolved optical switching technique, implemented in ambient air. The 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 a 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. Herein, the ability of this technique, initially designed for use in rare gases, is reported 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.