Abstract

The theory of a polarization-splitting directional coupler is developed with a coupled-mode approach for two interacting planar optical waveguides separated by a thin metal film. For TM guided modes and TE guided modes the coupled-mode equations governing the evolution of the modal amplitudes are obtained in an analytically closed form that provides a clear description of how the presence of a metal film brings about a strong polarization selectivity in the coupling between two optical waveguides. Representative numerical results show that, when silver or gold is used as the metal, polarization splitting with extinction ratios ∼ − 30 dB and throughput losses ∼0.2 dB is attainable in three typical wavelengths of 0.85, 1.30, and 1.55 μm.

© 1994 Optical Society of America

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