A NOVEL WAVE-GUIDE MACH-ZEHNDER INTERFEROMETER BASED ON MULTIMODE INTERFERENCE PHENOMENA

A novel form of Mach-Zehnder interferometer based on multimode interfe rence (MMI) phenomena in multimode waveguides is predicted and demonst rated. The interferometer is based on symmetrically feeding fundamenta l mode fields from two square waveguides, 2a X 2a, in cross section, i nto a multimode rectangular guide, 2a X 2b, (b > a). As a result of mu ltimode interference phenomena, depending on whether the input fields are ''in'' or ''out of'' phase, two completely different forms of resu ltant field pattern are produced at a distance of 2b2/lambda(c), along the multimode guide. The predictions are verified experimentally at 1 0.6 mum with hollow dielectric guides, but the underlying design conce pts are considered to be much more broadly applicable.