Intensity of parametric fluorescence pumped by ultrashort pulses

TL;DR

This paper analyzes the intensity of parametric fluorescence generated by ultrashort ultraviolet pulses, providing analytical and numerical insights into different conversion regimes and the effects of pulse duration and spatial divergence.

Contribution

It introduces a simple analytical model for photon flux in low-conversion regimes and uses numerical simulations to explore high-conversion regimes, highlighting the influence of pulse duration and beam divergence.

Findings

Photon flux can be accurately described by perturbative expressions even in non-perturbative regimes.

Maximum fluorescence intensity occurs at frequencies where pump and down-conversion group velocities match for short pulses.

Fluorescence intensity depends strongly on spatial divergence for small pump beams.

Abstract

We investigate intensity of the parametric down conversion of ultrashort, ultraviolet pulse both in a low- and high-conversion regime. In the first regime, we develop a simple analytical expressions for the photon flux of the fluorescence. Numerical simulations using three-dimensional stochastic Wigner method provide results in the latter regime. We find that the perturbative approximation for the photon flux as a function of the wavelength of the signal and the observation angle, quantitatively describes even the non-perturbative regime. For short pump pulses the intensity of the fluorescence is highest at frequencies where the group velocities of the pump and the down-conversion are equal. For longer pump pulses this requirement is gradually relaxed. Additionally, for small pump beams, the intensity strongly depends on the spatial divergence between interacting fields.