A. Crego | Searcharxiv

arXiv2026

Focusing and light collection effects on plasma-induced frequency-resolved optical switching (PI-FROSt) traces

Plasma-Induced Frequency-Resolved Optical Switching (PI-FROSt) is a promising and recently proposed phase-matching-free technique for characterising ultrafast pulses across broad spectral ranges. We investigate the mechanisms of PI-FROSt trace formation through numerical simulations and experimental validation. The results reveal that trace characteristics are highly sensitive to the relative focusing geometry between pump and probe pulses, as well as the spatial region selected for signal collection. Depending on these conditions, the interplay between plasma defocusing and positive lens-like nonlinear effects causes either intensity depletion or enhancement in the probe beam, flipping the PI-FROSt trace. Simulations demonstrate that optimal gate stability also depends strongly on the focusing scheme and the collecting region. This study highlights that precise spatial and temporal optimisation is essential to properly exploit the benefits of this broadband pulse characterisation technique.

physics.optics↗

arXiv2016

Laser-based X-ray and electron source for X-ray fluorescence studies

In this work we present a modification to conventional X-rays fluorescence using electrons as excitation source, and compare it with the traditional X-ray excitation for the study of pigments. For this purpose we have constructed a laser-based source capable to produce X-rays as well as electrons. Because of the large penetration depth of X-rays, the collected fluorescence signal is a combination of several material layers of the artwork under study. However electrons are stopped in the first layers allowing therefore a more superficial analysis. We show that the combination of both excitation sources can provide extremely valuable information about the structure of the artwork.

physics.ins-det↗