  We demonstrate electromagnetically induced transparency (EIT) in a sample of
rubidium atoms, trapped in an optical dipole trap. Mixing a small amount of
$\sigma^-$-polarized light to the weak $\sigma^+$-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.
