An analysis of photorefractive (PR) oscillators consisting of two facing fo
ur-wave mixing regions is carried out. The threshold and operation conditio
ns of different phase conjugate mirrors are discussed with the help of the
grating action method. In particular, the threshold and the operation of th
e two-zone double phase conjugate mirror (DPCM) is compared with other rela
ted PR oscillators, the interconnected ring, and different connected DPCM.
(C) 2001 Elsevier Science B.V. All rights reserved.