Mechanisms for optical oscillations in ferroelectric films

Under steady laser illumination, aperiodic spatio-temporal oscillations are observed in the light transmitted and reflected by parallel-sided samples of the ferroelectrics PMN (lead magnesium niobate, Pb(Mg1/3Nb2/3)O-3), PLZT (lanthanum doped lead zirconium titanate, Pb(Zr1-xTix)O-3:La), BNN (barium sodium niobate, Ba2NaNb5O15) and Ce:SBN (cerium doped strontium barium nio bate, Ce3+ :SrxBa1-xNb2O6). There are two distinct mechanisms for such osci llations, namely (1) unistable thermal focusing oscillations, which occur i n BNN and Ce:SBN and (2) bistable or multistable, Fabry-Perot switching osc illations, as observed in PMN and PLZT. The two types of oscillation have c haracteristic time scales differing by several orders of magnitude. We deri ve temperature profiles as a function of incident laser power, beamwidth an d sample thickness, which quantitatively predict the spatiotemporal charact eristics of the transmitted beam patterns. (C) 2001 Elsevier Science Ltd. A ll rights reserved.