Diffraction gratings in uniaxial crystals

The authors present a rigorous electromagnetic approach to wave diffraction at periodic interfaces between isotropic and uniaxial media. The incident wave vector is orthogonal to the grooves and is associated either with a wave incident from the isotropic medium or with a wave incident from the uniaxial one. The direction of the optic axis of the crystal is arbitrary. Propagation equations and boundary conditions are first formulated in terms of the components of the fields parallel to the grooves. Then, a coordinate transformation is used and the transformed equations are solved using a differential method. Computations have been made for cycloidal gratings made of sodium nitrate, considering two different cases: 1) a plane wave (TE or TM polarization) is incident from free space, and 2) a plane wave (ordinary or extraordinary) is incident from the crystal.<>