Study On Surface Solitons Of Optical Lattice And Uniform Nonlinear Medium Interface

Recently,light propagation in periodic optical systems such as waveguide arrays,optically-induced photonic lattices,and photonic crystals has attracted a lot of attention due to its physics and light-routing applications.Surface waves are a special type of waves,are confined at the very boundary between two different media,and have been researched widely.Surface solitons not only provide possibilities for optical routing and optical guiding.The thesis mainly research surface kink solitons in optical lattices,surface vector solitons in optical lattices and surface lattice solitons in photovoltaic-photorefractive crystals.The formation process and stability of the soliton are analyzed in detail.First of all,we research the surface kink solitons at the interface of optical lattices in defocusing nonlinear media.The research show that out-of-phase kink solitons and in-phase kink solitons exist in different region,and the region of existence of kinks does not occupy a whole gap.Modulation depth affects the generation of solitons and there is a corresponding threshold.Out-of-phase kink solitons are completely stable in a substantial part of their existence region,except that there is a relatively narrow unstable region near the first band lower boundary which is unstable due to oscillation.In-phase kink solitons were found to be always unstable,the oscillatory instabilities of solitons develop mainly on their tails inside the lattice and typically are so weak that solitons can propagate without any appreciable distortion over hundreds of diffraction lengths.Next,we research the surface vector lattice solitons in nonlinear media with harmonic transverse modulation of linear refractive index.The research show that in focusing media and defocusing media,odd vector solitons are stable in the considerable part of region where they exist and even vector solitons are stable in a little part of region where they exist.In focusing media,soliton stabilization occurs because of local increase of refractive index in neighboring lattice sites created by stable twisted component via XPM.In defocusing media,twisted first component can be stabilized through XPM interaction with the stable even second component.It was found that multi-humped vector solitons that are unstable in uniform media where XPM strength is higher than that of self-phase modulation,can also be stabilized by the lattice.Finally,we research the surface lattice solitons at the interface between the photonic lattices and the uniform photovoltaic-photorefractive crystals.The research show that surface lattice solitons exist only in the semi-infinite gap and are stable in the considerable part of moderate power region and unstable in the high,a little part of moderate,and low power regions.The power of surface lattice solitons decreases with an increase in the propagation constant in the high,considerable part of moderate,and low power regions and increases with the propagation constant in a little part of moderate power region.