Study Of Propagation Characteristics Of The Third-order Nonlinear Optical Lattice Soliton

It is of great scientific importance and practical value to study methods and techniques of propagation and control of the flow of light in periodic photonic structures. Especially,because of the unique features of the periodic photonic lattice, it can be effectively used to make high-performance devices based on bran-new theories and those would have been otherwise impossible. Therefore, it has important uses in the field of optics communication. The propagation and control of soliton in nonlinear Kerr optical lattice with harmonic modulation of refractive index are investigated analytically and numerically in this paper. And some innovative research results have been worked out.The forming conditions of lattice soliton from Gauss beam and the two modes of its stable propagation are obtained for the first time. According to the nonlinear Schr?dinger equations, by which propagation of optic lattice soliton is governed, the moment method is applied to deduce the evolution equations of lattice soliton's primary parameters. And conditions of formation and stable transmission of lattice soliton are found by further analysis. It is show that the initial power and the incident angle of the beam are important factors of formation and stable propagation of soliton. When the initial power matches with the beam width, a balance of diffraction and nonlinearity effects in propagation will be maintained and therefore the stable nonlinear lattice soliton comes into being. Due to the different values of incident angle, there are two different propagation formats. One case is that the beam is finally trapped in a guide-like channel and propagates stably along the channel when the launching angle is smaller than a critical value. Otherwise, it will propagate along the incident direction all along. The theoretical expression of the critical angle is acquired, showing that it rises with the increase of the depth and period of modulation of refractive index. Also, it increases as the beam width decreases.The method that initial chirp is used to control the propagation of lattice soliton is put forward for the first time. Under the condition that the beam is chirped, demands for soliton formation from Gauss beam and the evolution equations of the beam chirp in the propagation are obtained. The results show that linear spatial chirp upsets the balance between diffraction and nonlinearity, leading to radiation and thus destroying the condition for the formation of soliton, although it doesn't affect the central...