Abstract

Waveguide junctions are important for performing splitting and recombining of optical signals for guided-wave optics applications.¹ We describe a new class of multichannel waveguide junction which is useful for a variety of guided-wave manipulations. These junctions consist of an m-mode channel waveguide that branches into m single-mode channels, each having a different refractive-index profile. It is shown that each mode of these junctions becomes localized in a different single-mode channel as the channel separation increases. Thus, for sufficiently small branching angles, the junctions can route each mode of the multimode waveguide into a different output channel. When the junctions are excited from their single-mode channels end, they can serve to excite selectively each mode of the multimode waveguide. Furthermore, when both the width and refractive index of the single-mode channels are properly varied across the junction, the mode localization scheme becomes wavelength-dependent. Hence such junctions can operate as wavelength multiplexers/demultiplexers. Finally, by dynamically varying the refractive-index steps of the junction channels, e.g., via the electrooptic effect or optical nonlinearities, the waveguide junctions can perform multiport switching, modulation, and dynamic wavelength multiplexing/demultiplexing of guided waves.

© 1987 Optical Society of America