Energy transfer characteristics of photorefractive contradirectional two-wave mixing

Expressions of the coupling constant for contradirectional two-wave mixing (CTWM) have been derived. The calculations show that the energy transfer in CTWM has some unique characteristics different from the forward two-wave mixing (FTWM), in which the energy transfer direction is dependent on the two beam orientations with respect to the crystal polar axis and the sign of the light-induced carriers as well as the electro-optic coefficients. As a result, the CTWM can have a reverse energy transfer direction to the FTWM under a certain condition. The experimental results in two typical crystals of Rh-doped BaTiO3 and in Ce-doped strontium barium niobate (SBN:Ce) demonstrate the theoretical investigations very well. (C) 1997 Elsevier Science B.V.