In the last years, modeling, i.e. both analysis and synthesis in diffractive optics have been of great interest due to increasing amount of applications of diffractive elements in many optical areas. As far as the analysis problem is concerned, originally-used scalar theoretical methods became inapplicable soon, and more complicated treatments had to be developed. Among several rigorous methods for the analysis of diffraction characteristics of diffraction gratings proposed, the rigorous coupled-wave analysis (RCWA) has been employed and significantly improved the most since it is a deterministic, noniterative, relatively straightforward technique for obtaining the exact solution from the exact electromagnetic formulation [1-4]. Up to date, however, much less attention has been devoted to a specific part of the analysis problem, i.e. to the interpretation of the diffraction efficiency results obtained.

The purpose of this contribution is mainly to present, discuss and interpret on several examples new results obtained by using RCWA to model some interesting diffraction characteristics of a surface-relief grating. Our goals can be seen on two levels: (1) to show and discuss mechanisms of diffraction connected with volume phase synchronisms, together with the regions with typical diffraction regimes, types of volume phase synchronism, and their periodicity; and especially (2) to concentrate on a specific part of resonant processes in diffraction gratings, i.e. on the threshold effects which appear when a new-diffraction order is formed (resonant regions).

Such resonant regions are characterized by strong energy interchange processes (since new diffraction orders starts 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.

References

[2] Richter,I. - Fiala,P.: Mechanisms connected with a new diffraction order formation in surface-relief gratings submitted for publication to OPTIK - International Journal for Light and Electron Optics, 1999.

[3] Richter,I. - Fiala,P. - Ryzí,Z.: Physical interpretation of diffraction processes in surface-relief gratings EOS digest series Vol.22, p. 113, 1999 (EOS Topical Meeting on Diffractive Optics, Jena, Germany, August, 1999).

[4] Fiala,P. - Richter,I. - Ryzí,Z.: Analysis of diffraction processes in gratings SPIE Proceedings Vol.3820, p. 131, 1999.

This research has been supported by GA CR grant No. 202/98/P232.

Zpět