Photon wave-packet manipulation via dynamic EIT in multilayer structures
The control of light pulse propagation in matter is a key element of optical devices for fundamental science as well as for technological applications. In many cases, this is made difficult by the presence of competing effects like dispersion and absorption. Furthermore, the available time for manipulation is often limited by the very high propagation speed of light in conventional materials.
New perspectives in light propagation are opened by the observation of long-living coherence effects in optical media. Among these, Electromagnetically Induced Transparency (EIT) has been shown to produce strong modification to the response of optical media. The incoming light is coupled to a dark-state polariton which shows vanishing absorption and dispersion and whose group velocity can be controlled via the intensity of a control laser field.
We present a theoretical study of the dynamics of a light pulse propagating through a multilayer system consisting of alternating blocks of EIT media and vacuum. We study the effect of a dynamical modulation of the EIT control field on the shape of the wavepacket. Interesting effects due to the group velocity mismatch at the interfaces are found. Modulation schemes that can be realized in ultracold atomic samples with standard experimental techniques are proposed and discussed: dilute atomic clouds are in fact particularly interesting because of the significant reduction of dephasing processes with respect to solid-state systems.