Coupled-wave method for systems with directional energy transfer

The application of a coupled-wave method to a distributed-coupling structure with directional energy transfer from one of the coupled waves to another is discussed. A consequence of the method is the possibility of realizing optical elements the characteristics of which are dependent on the direction of wave propagation. Consideration is given to a description of the wave-coupling process, dissipation in distributed coupling structures, and distributed coupling structures on a waveguide corrugation. The peculiarity of the optical elements is that they are realized without magneto-optical materials but are made using a distributed coupling structure of any type. Examples of the possible applications of directional coupling are given and include nonreciprocal optical elements, optical logic, a grating coupler, a radiative Bragg mirror, and an asymmetrical DFB laser.