Spectral Pulse Distortion from Two-Beam Coupling of Sub-Picosecond Pulses in a Photorefractive Crystal

Abstract

Consider the coupling between two trains of mode-locked pulses in a photorefractive crystal. Let each optical pulse be so weak that it takes a large number of pulses to built up a quasi-steady-state refractive-index grating in the crystal. In this case the shape of the pulses will change as the result of beam coupling.1 The temporal pulse shape changes for two reasons. First, interference between the diffracted pulse and the transmitted pulse alters the pulse shape, as shown in Fig. 1. Second, only a portion of each pulse's full frequency spectrum is diffracted by the volume photorefractive grating.