Enhanced diffraction efficiency of gratings in multilayers

Computations with the rigorous differential method show that single grating s made by ion implantation have a diffraction efficiency in the + 1 transmi tted order under TE illumination of only 0.78%. The insertion of such grati ngs into multilayer dielectric Fabry-Perot cavities leads to an enhancement of the free-space diffraction efficiency. Different designs for the multil ayer are considered. An 18.8% efficiency is reached with Ii-layer mirrors. This result is obtained by optimization of the thickness of the spacer of t he Fabry-Perot cavity that contains the grating and centering of the wavele ngth of the mirrors. The dependence of optical properties of the structure on the various optogeometrical parameters of the structure is discussed. (C ) 2000 Optical Society of America OCIS codes: 050.1950, 050.1970, 050.2230.