An analysis of the three-valence model of photorefraction

In this paper we present an analysis of the three-valence model of photorefraction. The basic equations of the model are studied and solved to find zero- and first-order solutions in the steady state, including expressions for the space-charge field and the effective trap density. The intensity dependence of the solutions for the population densities and space-charge field are analysed and discussed for varying proportions of the different valence states in the material, and the influence of some important material parameters considered. The possible applications of these results to the experimental characterisation of three-valence-state materials are discussed and some comparisons are made between the three-valence and the two-independent-centre models of photorefraction. Received: 17 November 1998 / Revised version: 8 January 1999 / Published online: 31 March 1999