  Magnetoelectric coupling in multiferroic materials opens new routes to
control the propagation of light. The new effects arise due to dynamic
magnetoelectric susceptibility that cross-couples the electric and magnetic
fields of light and modifies the solutions of Maxwell equations in media. In
this paper two major effects will be considered in detail: optical activity and
asymmetric propagation. In case of optical activity the polarization plane of
the input radiation rotates by an angle proportional to the magnetoelectric
susceptibility. The asymmetric propagation is a counter-intuitive phenomenon
and it represents different transmission coefficients for forward and backward
directions. Both effects are especially strong close to resonance frequencies
of electromagnons, i.e. excitations in multiferroic materials that reveal
simultaneous electric and magnetic character.
