Femtosecond Photoionization of Atoms under Noise

TL;DR

This paper explores how adding noise to femtosecond laser pulses can enhance atomic ionization, revealing a stochastic resonance effect and suggesting practical experimental implementations with broadband chaotic light.

Contribution

It demonstrates noise-induced ionization enhancement in atoms under weak femtosecond pulses and analyzes the underlying mechanisms, introducing a stochastic resonance perspective.

Findings

Noise addition significantly increases ionization probability.

A stochastic resonance-like curve shows an optimal noise level.

Broadband chaotic light can replicate white noise effects.

Abstract

We investigate the effect of incoherent perturbations on atomic photoionization due to a femtosecond mid-infrared laser pulse by solving the time-dependent stochastic Schr\"odinger equation. For a weak laser pulse which causes almost no ionization, an addition of a Gaussian white noise to the pulse leads to a significantly enhanced ionization probability. Tuning the noise level, a stochastic resonance-like curve is observed showing the existence of an optimum noise for a given laser pulse. Besides studying the sensitivity of the obtained enhancement curve on the pulse parameters, such as the pulse duration and peak amplitude, we suggest that experimentally realizable broadband chaotic light can also be used instead of the white noise to observe similar features. The underlying enhancement mechanism is analyzed in the frequency-domain by computing a frequency-resolved atomic gain profile, as well as in the time-domain by controlling the relative delay between the action of the laser pulse and noise.