A ray approach to a problem of corrugated waveguide excitation by an external light beam

Excitation process of a corrugated optical waveguide is analyzed with using notions about zigzag light propagation in a waveguide layer. A plane incident wave is shown to be undergone with total reflection at a moment of maximum excitation in the case of infinite length of a grid on the waveguide. Conditions of optimal excitation of a corrugated waveguide are found in an approximation of geometrical optics. In the general case (noncollinear) a new third condition is obtained for excitation optimum and its physical interpretation is given.