Time-frequency mapping of two-colour photoemission driven by harmonic radiation

TL;DR

This paper introduces a simplified model and analytical method for real-time estimation of pulse dispersion in two-color photoemission experiments driven by harmonic radiation, enhancing pulse characterization techniques.

Contribution

It presents a new analytical approach to interpret time-frequency mapping of sideband signals and estimate pulse dispersion without iterative algorithms.

Findings

Derived an analytical solution for pulse dispersion estimation.

Proposed a real-time, non-iterative characterization method.

Linked temporal dispersion directly to spectrogram shape.

Abstract

The use of few-femtosecond, extreme ultraviolet (XUV) pulses, produced by high-order harmonic generation, in combination with few-femtosecond infrared (IR) pulses in pump-probe experiments has great potential to disclose ultrafast dynamics in molecules, nanostructures and solids. A crucial prerequisite is a reliable characterization of the temporal properties of the XUV and IR pulses. Several techniques have been developed. The majority of them applies phase reconstruction algorithms to a photoelectron spectrogram obtained by ionizing an atomic target in a pump-probe fashion. If the ionizing radiation is a single harmonic, all the information is encoded in a two-color two-photon signal called sideband (SB). In this work, we present a simplified model to interpret the time-frequency mapping of the SB signal and we show that the temporal dispersion of the pulses directly maps onto the shape of its spectrogram. Finally, we derive an analytical solution, which allows us to propose a novel procedure to estimate the second-order dispersion of the XUV and IR pulses in real time and with no need for iterative algorithms.