Electromagnetically induced transparency with Laguerre–Gaussian modes in ultracold rubidium

We demonstrate electromagnetically induced transparency with the control laser in a Laguerre–Gaussian mode. The transmission spectrum is studied in an ultracold gas for the D2 line in both 85Rb and 87Rb, where the decoherence due to diffusion of the atomic medium is negligible. We compare these results to a similar configuration, but with the control laser in the fundamental laser mode. We model the transmission of a probe laser under both configurations, and we find good agreement with the experiment. We conclude that the use of Laguerre–Gaussian modes in electromagnetically induced transparency results in narrower resonance linewidths as compared to uniform control laser intensity. The narrowing of the linewidth is caused by the spatial distribution of the Laguerre–Gaussian intensity profile.