  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 $^{85}$Rb and $^{87}$Rb, 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.

Atomic Physics