Solitons in two- and three-dimensional crystals at Fermi resonance of optical modes

It is shown that soliton excitations of the peak, crater, and dark types, previously found by authors only in one-dimensional crystals, exist in two- and three-dimensional crystal systems of the superlattice type at Fermi resonance of modes of adjoining crystals. An analytical solution for the central part of soliton envelopes is presented. A numerical calculation gives results coinciding with the analytical solution in the central part of the solitons and demonstrates the presence of oscillations of the envelopes on the wings of peak and crater solitons in two- and three-dimensional crystals, which are not observed in one-dimensional crystals. (C) 1999 American Institute of Physics. [S1063-7834(99)03104-4].