  We investigate the propagation of light with ultra low group velocity in a
Bose-Einstein condensate where the phase is not uniform. The light is shown to
couple strongly to the phase gradient of the condensate. The interaction
between the light and the condensate enables us to perform a phase imprinting
where the phase of the condensate is imprinted on the light. We illustrate the
effect by showing how one can measure the fluctuating phase in an elongated
quasicondensate.
