Analysis of grating-assisted backward coupling employing the unified coupled-mode formalism

Grating-assisted backward coupling between two parallel waveguides is analy zed with a set of four coupled equations. The equations were recently deriv ed by a unified approach that is appropriate for other coupling problems as well. Examples include three different operation regions and provide for t he field variation along the guides as well as for the reflectivity and tra nsmission coefficients. It is shown that the reduction of the four-wave cou pling problem to a set of two coupled equations is possible only for some s pecific cases and at the cost of reduced accuracy. The model may be especia lly useful for the design of optical components for various applications su ch as optical switching and multiplexing. (C) 1999 Optical Society of Ameri ca [S0740-3232(99)03405-5].