Determination of leaky modes in planar multilayer waveguides

In this letter, we present a numerically exact and simple novel technique for the determination of leaky modes in planar multilayer waveguides. The technique uses a dispersion equation provided by the thin-film transfer matrix method. Complex roots, that correspond to leaky modes, are searched on the basis of a smooth transition between the bound modes of a closed waveguide and the leaky modes of an open waveguide. The technique does not use any approximation.