Abstract

The power transfer between waveguides in a codirectional coupler depends on the interaction length, the coupling coefficient, and the wavelength.¹ Since power transfer is wavelength dependent, these devices act as filters or switches. The filter response can be controlled by varying the coupling coefficient along the propagation direction. Since the coupling coefficient increases exponentially with waveguide separation, this variation may be realized by tapering the spacing between the guides. The filtering action of waveguide directional couplers is modeled by the following pair of first-order coupled mode equations.

© 1990 Optical Society of America