D. Engin et al., AMPLITUDE-EQUATION FORMALISM FOR 4-WAVE-MIXING GEOMETRY WITH TRANSMISSION GRATINGS, Journal of the Optical Society of America. B, Optical physics, 14(12), 1997, pp. 3349-3362
An amplitude equation is derived for a four-wave-mixing geometry with
nearly counterpropagating, mutually incoherent, nondiffracting pump be
ams, spatially overlapping in a photorefractive material with a nonloc
al response. This equation extends the earlier linear two-dimensional
theory to the weakly nonlinear regime. The analysis also starts from a
more complete equation for the photorefractive effect, which leads to
the prediction of novel effects especially apparent in the nonlinear
regime. Precise predictions for the spatiotemporal behavior of the gra
ting amplitude in the nonlinear regime are presented. The range of val
idity of the amplitude equation is studied. The characteristics of the
instability in the nonlinear regime are analyzed through a front-sele
ction analysis. (C) 1997 Optical Society of America [S0740-3224(97)018
12-2].