Abstract

A directional coupler consisting of three parallel waveguides is analyzed. The radiation is coupled between the two external guides, while the center-guide refraction index controls the coupling. By means of a coupled-mode analysis, a cross-and-bar diagram is drawn for the device, and regions are located in it for near-complete energy transfer between the guides. A rigorous mode analysis is presented for a three-guide layered structure, and the radiation-transfer process is numerically simulated for single-mode as well as for highly multimode guides. Although the analysis is carried out only for slab waveguides, the results are applicable for channel guides as well when the method of effective index approximation is utilized.

© 1984 Optical Society of America

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