Spatiotemporal couplings under tight focusing of an ultrashort laser pulse by an off-axis parabolic mirror
Phys. Rev. A 114, 033527 – Published 28 September, 2026
DOI: https://doi.org/10.1103/y1tj-8ksc
Abstract
The tight focusing of ultrashort laser pulses by an off-axis parabolic (OAP) mirror beyond the slowly varying temporal envelope (SVTE) approximation is studied. Nonmonochromatic effects are found to generate appreciable spatiotemporal coupling even near the focus, and the SVTE approximation leads to an overestimate of the pulse powers in the focal spot by up to 25%. To describe this regime, we develop a model based on Stratton-Chu integrals and use it to quantify the spatiotemporal coupling effects depending on the laser pulse duration, its position, and mirror off-axis angle. A comparison with the SVTE description yields an explicit criterion for the SVTE approximation. The fields, predicted by the nonmonochromatic model, are validated in three-dimensional smilei simulations, providing a compact framework for modeling few-femtosecond OAP focusing in high-intensity laser-plasma experiments.
