Periodic diffractive optics with curved phases

We give 3-scales WKB asymptotics for nonlinear hyperbolic systems with vari able coefficients. Our profiles are transported, at the slower scale, along the rays of geometric optics,and are diffracted, at the intermediate scale , according to some (variable coefficients) Schrodinger equation. (C) 2001 Academie des sciences/Editions scientifiques et medicales Elsevier SAS.