Field microstructure and temporal and spatial instability of photonic Bloch waves in nonlinear periodic media

(Received 14 March 1994, accepted 10 May 1994)

Abstract
The nonlinear dispersion relation of monochromatic optical Bloch modes in a periodic half-space is derived for both normal and oblique incidence. It is shown that strong nonlinear beam steering can occur in the vicinity of the Bragg condition. By studying the field microstructure, and making use of diagrams of wavevector versus frequency, a fresh perspective is gained on the physical mechanisms that govern the behaviour of light in nonlinear periodic media. A linearised analysis is used to identify parameter ranges of temporal and spatial instability, and to quantify the gain of the associated modulational instability.