Temporal optical processes in a Rydberg gas

In this paper, we discuss a variety of temporal optical phenomena in a gas of Rydberg atoms, which can take place in the presence of varying quasi-static electric fields and control laser beams. This includes the discussion of temporal spectral changes of probe laser beams, associated with purely temporal processes created by Stark and ac-Stark shifts of the atomic susceptibility. Such changes include phase and group velocity perturbations, time delays, frequency shifts, and other temporal changes of the transmitted and reflected probe signals. We mainly focus on ultrafast temporal transitions, known as time-refraction, and their specific signatures, which envolve the occurrence of a temporally induced reflection coefficient. Our model assumes that the temporal variations of the applied Stark shifts are much shorter than the Rydberg life-times. We also discuss the Rydberg atom response to ultrashort laser pulses, in the attosecond time domain, and derive the corresponding atomic susceptibilities. Finally, the optical properties of a temporally perturbed Rydberg-EIT configuration, and the expected influence of dipole blockade are considered. This could eventually lead to new experimental studies in Rydberg optics.