  We present a theoretical study of the dispersion and energy properties of the
eigenwaves (TE- and TM- modes) in a four-layer structure composed of a
magneto-optical yttrium iron garnet guiding layer on a dielectric substrate
covered by a planar nanocomposite guiding multilayer. The bigyrotropic
properties of yttrium-iron garnet are taken into account for obtaining the
dispersion equation and an original algorithm for the guided modes
identification is proposed. We demonstrated the polarization switching of TE-
and TM-modes dependent on the geometrical parameters of the guiding layers. The
dispersion diagrams and field profiles are used to illustrate the change of
propagation properties with variation of the multilayer thickness ratio of the
nanocomposite layers. The energy flux distributions across the structure are
calculated and the conditions of the optimal guiding regime are obtained. The
power switching ratio in the waveguide layers of about 6 dB for the wavelength
range of 100 nm is shown to be achieved.
