COUPLING EFFICIENCY OF BUTT-JOINED PLANAR WAVE-GUIDES WITH SIMULTANEOUS TILT AND TRANSVERSE OFFSET

An efficient method has been proposed for evaluating the;junction loss between two nonidentical arbitrarily graded-index planar optical wave guides caused by simultaneous transverse and angular misalignments. Th e salient feature of the method is an exact representation of the moda l fields which is particularly adapted to loss evaluation at imperfect junctions. The power transmission coefficient at the junction is expr essed via the overlap integral method as a weighted sum of simple Lagu erre-Gaussian functions, the weight factors being determined by solvin g a linear matrix eigenvalue problem. The present formulation has a ve ry broad scope of validity and can be used for the modal analysis of i ntegrated optical planar components such as waveguide lenses and to es timate the coupling efficiency of more practical fiber-to-channel butt -joints. The method can also be used to test the accuracies of other a pproximate methods such as those based on the Gaussian approximation o f the lowest order planar waveguide mode.