Narrow bandwidth electromagnetically induced transparency in optically trapped atoms

We demonstrate electromagnetically induced transparency (EIT) in a sample of rubidium atoms, trapped in an optical dipole trap. Mixing a small amount of σ − -polarized light to the weak σ + -polarized probe pulses, we are able to measure the absorptive and dispersive properties of the atomic medium at the same time. Features as small as 4 kHz have been detected on an absorption line with 20 MHz line width. (Some figures in this article are in colour only in the electronic version)