Ray picture for prism–film coupling

A description of the prism–film coupler, with use of the ray picture, was introduced by Tien and Ulrich [ J. Opt. Soc. Am.60, 1325– 1336 ( 1970)]. Here a discussion of this model is given, and it is argued that the effect of the Goos–Hanchen shift cannot be neglected in general. Further, relatively simple expressions are given for the computation of the coupling efficiency of a prism-loaded planar structure as a function of the angle of incidence of the incoming beam. Computational results are presented and compared with those of other methods.