This paper presents an experimental investigation of the propagation of a single laser pulse in a photorefractive crystal on a nanosecond time-scale. A time resolved observation of one doubled YAG:Nd 5 ns pulse self-focusing in electrically biased Bi12TiO20(BTO) is reported. Systematic measurements have been achieved in order to analyse the influence of different parameters such as the external applied electric field, the incident fluence, the input polarisation. Hints are then given to a theoretical modelling of pulsed self-focusing.