WAVE-GUIDE BEAM-SPLITTERS AND RECOMBINERS BASED ON MULTIMODE PROPAGATION PHENOMENA

Novel waveguide beam splitters and recombiners based on multimode propagation phenomena in hollow step-index wave guides are predicted and demonstrated. The splitter designs are based on symmetrically feeding the fundamental-mode field from a square cross-section waveguide, 2a x 2a, into a multimode rectangular guide, 2a x 2b (b > a). As a result of multimode superposition phenomena, unique transverse-field patterns representing different-order multiway splitting of the input field occur at predictable positions along the rectangular-guide axis. The predictions are verified experimentally at 10.6-mu-m with hollow dielectric waveguides but are considered to be more widely applicable.