Mechanisms connected with a new diffraction order formation in surface-relief gratings

This contribution concentrates on modeling of diffraction processes in surf aces-relief gratings, occurring particularly within resonant regions. First , the characterization of mechanisms and diffraction processes is briefly p resented, together with the regions with typical diffraction regimes, types of volume phase synchronism and their periodicity. The resonant regions ar e characterized by strong energy interchange processes (since new diffracti on orders start to become propagating), the diffraction efficiency behavior within such a region is described and interpreted. Two main subregions of resonant regions are found: (1) the region with effective behavior "mound" and (2) the region with resonant coupling. The conditions for the existence of the first subregion are presented and explained.