The population of Rydberg states as a function of the ellipticity of an intense field in the quasi-static limit
The creation of Rydberg states following interaction with an intense field is currently of topical interest in particular with respect to the proposed mechanisms at their origin, such as frustrated tunnelling or multi–‐photon excitation. We study the population of Rydberg states as a function of the ellipticity of the laser field and of its intensity, for long and short pulses, and we compare our results with recent theory and experiment.
For linear polarization, by solving the time dependent Schrödinger equation (TDSE), we have shown that multi–‐photon excitation plays an important role in explaining the yield of Rydberg states as a function of intensity and pulse length for intense laser fields in the quasi–‐static limit (with wavelengths as long as 1800 nm). For elliptically polarized light, we have compared our quantum results with semi–‐classical approaches and although we obtain a gaussian distribution as a function of ellipticity as predicted semi–‐classically, we see important differences with semi–‐classical predictions in the dependence on the pulse length and the intensity of the pulse.
The STSM has led to a new paper on population trapping in the quasi–‐static limit for linearly polarized pulses which has been sent for publication to Physical Review A. A second paper on the dependence on the ellipticity of the polarization of the pulse is currently in preparation.
Figure: The total excited state probability as a function of ellipticity for an 800 nm laser pulse with an intensity of 2×1014 W/cm2 and for two pulse lengths (LHS) and (RHS) for a fixed pulse length but at two different intensities.