EVALUATION OF DIFFRACTION LOSS IN PRISM LIGHT GUIDES BY FINITE-DIFFERENCE TIME-DOMAIN FIELD MODELING

Prism light guides are hollow dielectric tubes that use prismatic face ts to guide light by means of total internal reflection. An unresolved problem has been to determine the magnitude of loss caused by diffrac tion in prism Light guides. Neither experimental measurement nor an an alytical solution has yet been achieved, so we attacked the problem nu merically, in two steps. First, we found a way to represent such a tra nsitionally invariant three-dimensional system as an equivalent two-di mensional problem. Second, we employed the finite-difference time-doma in algorithm, with periodic boundary conditions, to yield a computatio n problem of manageable size. We found that the diffraction-induced tr ansmissivity of a prism light guide wall is of the order of the wavele ngth divided by the prism size-a result that has encouraging practical implications. (C) 1998 Optical Society of America.