A photorefractive oscillator in a c-cut Ce-doped BaTiO3 plate is demonstrat
ed. The output characters of this oscillator show that the contradirectiona
l two-wave mixing (CTWM) is an important interaction as well as forward two
-wave mixing (FTWM). According to the experimental results, the oscillation
conditions of this oscillator and a new method to determine the photorefra
ctive index are presented.