The report is devoted to the optical properties of glass-nanocomposites - glasses containing metal nanoparticles. Methods for the creation and modification of nanocomposites, as well as the technique for creating diffraction structures based on them are considered. A theoretical analysis of the spectral properties of these structures shows that they demonstrate both the phase and amplitude character, while heavily influenced by the excitation of waveguide and polariton modes in glass-nanocomposites.