The Study Of Spatial Optical Solitons In Nonlocal Nonlinear Materials

Spatial optical solitons represent beams, which propagate in nonlinear media without changing their profile. Their existence is a result of an interplay between size-determined diffraction and nonlinearity-induced phase modulation. There has recently been strong interest in the so-called nonlocal nonlinearity, because of its inherent features in many physical systems such as liquid crystals. The study of various kinds of nonlocal solitons have opened up a new direction in nonlinear science and led to many novel topics, providing theoretical support for further understanding of spatial solitons.We investigate theoretically the propagation of various kinds of solitons in material with nonlocal nonlinearity, including incoherent spatial solitons and elliptic incoherent solitons in highly nonlocal medium with noninstantaneous Kerr nonlinearity, dark solitons and the interaction of dark solitons in nonlocal materials with an arbitrary degree of nonlocality, and nonlocal complex solitons: vector dipole solitons and vector-necklace-ring soliton clusters.The main results are as follows:(1) We study the properties of one dimension incoherent accessible solitons in strongly nonlocal media with noninstantaneous Kerr nonlinearity. Following the coherent density theory, we obtain an exact solution of such incoherent solitons. The spatial width of the incoherent solitons is related to the incoherent angular power spectrum ? 0 as well as the incident power. The evolution properties of the intensity profile and the coherence characteristics are also discussed in detail when the solitons undergo periodic oscillation.(2) The propagation of elliptic incoherent beam in strongly nonlocal media with noninstantaneous anisotropic Kerr nonlinearity is fully investigated. Using the mutual coherence function approach, we obtain the existence curve of such solitons and an interesting outcome: correlation characteristics of the elliptic incoherent solitons can be anisotropic as well as isotropic. When the existence conditions of solitons are not satisfied, the elliptic incoherent beam will undergo periodic oscillation. Nonstationary evolution behaviors of the elliptic beam are shown in detail by numerical calculation. It is also obtained that the oscillation periods of the beam in x and y direction are different and the elliptic beam will become circular at some propagation distance under special conditions.(3) We investigate properties of dark solitons in nonlocal materials with an arbitrary degree of nonlocality. We employ the variational technique and describe dark solitons, for the first time to our knowledge, in the whole range of degree of nonlocality.(4) We investigate theoretically the interaction of dark solitons in materials with a spatially nonlocal nonlinearity. In particular we do this analytically and for arbitrary degree of nonlocality. We employ the variational technique to show that nonlocality induces an attractive force in the otherwise repulsive soliton interaction.(5) We study properties of the vector multipole solitons in nonlocal media with an arbitrary degree of nonlocality, such as two-dimensional vector dipole solitons and vector-necklace-ring solitons. We apply the variational approach to find the exact solution of such solitons and investigate their stability by using directly numerical simulations. We show that the nonlocality induces an attractive force, in combination with vector property can completely stabilize the vector mulitpole solitons.