Full characterization of the photorefractive bright soliton formation process using a digital holographic technique

An extensive characterization of the photorefractive bright soliton writing process in a lithium niobate crystal is presented. An interferometric approach based on a digital holographic technique has been used to reconstruct the complex wavefield at the exit face of the crystal. Temporal evolution of both intensity and phase profile of the writing beam has been analysed. The effective changes of the refractive index of the medium during the writing process and after the soliton formation are determined from the optical phase distribution. This method provides a reliable way to observe the process of soliton formation, whereas the determination of the intensity distribution of the output beam does not show clearly whether the soliton regime has been achieved or not. Furthermore, a detailed analysis of the soliton in a steady-state situation and under different writing conditions is presented and discussed.