Research On The Soliton Sequence In Photovoltaic Photorefractive Crystals

The research of photorefractive spatial solitons is currently one of the briskest subjects and has been widely studied in nonlinear optics.When nonlinear optical wave propagate in periodic structures such as arrays made in photovoltaic photorefractive crystals,the nonlinear effects and the diffraction effects produced by optical wave may achieve a exactly balance,optical wave will forward propagate without change of form and the propagation constants falls within the gap,which forms gap solitons.Gap solitons has considerable features of formation at very low power,fast response and large nonlinearity,it makes gap solitons has potential application in all optical communicational,optical switching,optical routing,optical photonic devices.In this thesis,characteristics of the sequence of odd and even gap solitons and twisted solitons are analyzed and simulation in detail by such means as plane wave expansion method,modified squared operator iteration method,beam propagation method based on split step fourier methods,fourier collocation method.Firstly,we analyze that the formation an odd and even numbered sequence of multiple gap solitons and twisted solitons supported by waveguide arrays made in self-focusing photovoltaic-photorefractive crystals imprinted harmonic transverse linear modulation of the refractive index based on Nonlinear Schrodinger equation.These gap solitons and twisted solitons only exist in the semi-infinite gap,the energy flow value of these gap solitons and twisted solitons increases with an increase in the propagation constants and increases with the order of these solitons when propagation constants is fixed.The existence domain of these odd and even numbered gap solitons decreases with decreasing the lattice depth.The intensities of side and middle lobes of the higher-order gap soliton can be controlled by changing the propagation constants.The middle lobes of the higher-order gap soliton are the small intensity,which decrease with the propagation constants.The existence domain of these odd and even numbered twisted solitons shrinks with growth the saturation parameters.The lateral side lobes of the higher-order twisted soliton are the small intensity,which decrease with the propagation constant.The stability of these gap solitons and twisted solitons has been investigated numerically and they are proved to be stable.On the other hand,we show that the formation an odd and even numbered sequence of multiple gap solitons and twisted solitons supported by waveguide arrays made in self-defocusing photovoltaic-photorefractive crystals.These gap solitons and twisted solitons only exist in the first-finite gap.the energy flow value of these gap solitons and twisted solitons decreases with an increase in the propagation constant and increases with the order of these solitons when propagation constants is fixed.The existence domain of these odd and even numbered gap solitons decreases also with decreasing the lattice depth.The side lobes of the higher-order gap soliton are the small intensity,which increase with the propagation constant.The existence domain of these odd and even numbered twisted solitons also shrinks with growth the saturation parameters.The middle lobes of the higher-order twisted soliton are the small intensity,which increase with the propagation constant.The stability of these gap solitons and twisted solitons has been investigated numerically and it has been found that gap soliton are stable,twisted solitons are unstable.