Propagation of light in a system of two radiatively coupled waveguides

A system of waveguides coupled radiatively by leaky modes is considered. The dispersion curves and the dependence of the coupling length on the parameters of the system are calculated. The optimal distance between the waveguides, corresponding to the maximum degree of radiation transfer, is determined. The coupling length then has its maximum value L_c^max = π/2α_rad, where α_rad is the coefficient representing the radiative losses in a single waveguide (decay coefficient of a waveguide mode). The results are given of an experimental study in which radiation was transferred in a system of radiatively coupled waveguides separated by a distance of 95 μm.