Temporal dynamics of two-beam coupling and the origin of compensation photorefractive gratings in Sn 2 P 2 S 6 :Sb

The photorefractive effect in Sn2P2S6 (SPS) is caused by a spatial redistribution of both positively charged and negatively charged carriers, which leads to the formation of two out-of-phase space charge gratings that partially compensate each other in the steady state. The unusual intensity dependence of the compensation grating buildup time is reported in this article for antimony doped SPS; it is explained by the thermal excitation of electrons into conduction band from the optically recharged Sb3+ → Sb2+ impurity ions.