Resonant diffraction coupling between corrugated and regular optical waveguides

A study is reported of resonant diffraction coupling between two optical waveguides when a corrugated sinusoidal grating is formed on one of them. A theory is developed for diffused waveguides characterized by a smoothly inhomogeneous transverse distribution of the refractive index, dealing with the cases of both H and E waves. The dependences of the resonant coupling coefficient on the surface wavelength and on the difference between the effective refractive indices are deduced for waves in waveguides with different transverse refractive index profiles.