Abstract

We present a design technique for accurately predicting coupling efficiency in guided-wave applications of gratings. We approach the problem by separating the planar waveguide and diffraction grating. The wave guiding is treated by ray optics techniques, and grating diffraction is treated by rigorous diffraction grating theory or direct measurement. In this way, we get more feeling for the working of the grating as a diffraction element and how it interacts with the waveguide structure. When the grating groove depth is small our results agree with the phenomenological expressions given by Zory¹ and the result of coupled-mode theory by Yariv.² It is shown that the phase difference between reflected plane waves with and without the presence of the grating is important for determining the reflection coefficient of a distributed feedback reflector.

© 1987 Optical Society of America