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The derivations of several conservation laws of the generalized nonlocal nonlinear Schrodinger equation are pre- sented. These invariants are the number of particles, the momentum, the angular momentum and the Hamiltonian in the quantum mechanical analogy. The Lagrangian is also presented.

The propagation and interaction properties of optical vortex solitons in a self-defocusing Kerr-type nonlocal medium are investigated by the numerical simulation method. It is indicated that the singly charged vortices are stable and the multicharged vortices are topologically unstable in both the nonlocal and local cases. And in the nonlocal and local cases the point vortices model is applicable for describing the interactions of vortices provided that the interval distances between vortices are much larger than the size of the core of the vortices. However, vortices interact differently in short distance, depending on the nonlocality, and the larger the characteristic nonlocal respond length, the larger the rotating period of two singly charged vortices.

The interaction between photovoltaic spatial solitons with difference wavelengths in photovoltaic-photorefractive crystals is investigated by numerical method. Our numerical study indicates that the interaction between these solitons is inelastic, and these solitons keep their shapes only within some propagation distance. Besides the attraction with each other, the energy of soliton would be coupled from one waveguide to other waveguide during propagation.

The parallel interaction between two photovoltaic spatial solitons of dark and dark as well as dark and bright with different wavelengths is investigated by numerical method. Our numerical study indicates that the dark solitons can both remain as quasi soliton form in certain distance while they propagate coaxially. H owever,they attract each other while closely overlapping. And they have a conver gent effect on each other at the slowly varying region of optical field while in larger separations. For the case of interaction between dark and bright, the br igh t one may experience compression, expansion or energy transfer depending on thei r mutual separation.The physical interpretation of this solitons interaction is also given in terms of the refractive index waveguide they jointly induce.

The photovoltaic effect of a background beam do not affect the spatial-charge field in a photovoltaic crystal with a constant external applied field, but has an effect on the current density in the crystal.If the crystal is connected with an external circuit which includes a resistor and a constant voltage source, the photovoltaic effect of the background beam will affect the full width at half maximum of the solitons, even switch the bright solitons, to the dark solitons, or vice versa.