Modulational instability of incoherently coupled beams in azobenzene-containing polymer with photoisomerization nonlinearity

The modulational instability of two incoherently coupled beams in azobenzene-containing polymer with photoisomerization nonlinearity is investigated analytically and numerically. Our results show that as a precursor to spatial optical soliton formation, modulational instability can be adjusted and controlled by the wavelength combinations of the signal and background beams. We also discuss the dependences of strength of modulational instability on intensities of two signal beams and background beam. These findings make it possible to predict the formation of incoherently coupled soliton pairs in azobenzene-containing polymer.     

Internal mode of incoherent photovoltaic vector solitons

The internal modes of incoherent vector solitons (IVSs) in photovoltaic photorefractive materials are investigated in the framework of coupled nonlinear Schr\"{o}dinger equations. It is found that there is a pair of internal modes corresponding to a bright--bright IVS. The propagation dynamics of the bright-bright IVS perturbed by the internal modes is simulated by numerical method.     

光折变空间孤子研究进展

光折变空间孤子足目前非线性光学领域的热点课题之一.光折变空间孤子以其低功率、快响应和强非线性效应等特点以及在全光开关、光波导、光互联等方面的潜在应用而受到人们的关注.文章详细介绍了光折变空间孤子的产生机制并综述其研究历史及发展现状.     

相干光伏空间孤子非对称碰撞研究

采用数值方法研究了三个呈非对称分布的相干光伏空间孤子碰撞相互作用.结果表明,随着信号光的入射角度在一定范围内逐渐改变,三个孤子在晶体中碰撞后会产生孤子的分裂或湮没现象.当孤子碰撞后出现分裂或湮没时,若保持孤子的碰撞角度不变,改变其中任意一个孤子的初始相对相位,孤子的碰撞行为也将随之迅速改变,产生新的孤子分裂、湮没或其他碰撞现象.另外,研究结果还表明,作为具有不可积哈密顿系统特性的光伏孤子,其小角度碰撞过程中动量和能量仍然是守恒的. 关键词： 光伏孤子 非对称碰撞 分裂 湮没     

Bloch oscillation and Landau\ben Zener tunnelling in a modulated optical lattice in a photovoltaic photorefractive crystal

We theoretically study the beam dynamical behaviour in a modulated optical lattice with a quadratic potential in a photovoltaic photorefractive crystal.We find that two different Bloch oscillation patterns appear for the excitation of both broad and narrow light beams.One kind of optical Landau–Zener tunnelling also appears upon the Bloch oscillation and can be controlled by adjusting the parameter of the optical lattice.Unlike the case of linear potential,the energy radiation due to Landau–Zener tunnelling can be confined in modulated lattices of this kind.For high input intensity levels,the Landau–Zener tunnelling is suppressed by the photovoltaic photorefractive nonlinearity and a symmetry breaking of beam propagation from the modulational instability appears.     

光伏暗孤子和灰孤子的自偏转

分别用数值法和微扰法研究了考虑背景光时光伏暗空间孤子的自偏转特性.与亮孤子不同，暗孤子光束中心的运动轨迹不为抛物线.在归一化的直角坐标系(ξ,ζ)中，暗孤子朝ξ>0的方向偏转；同时，暗孤子光束中心光强发生改变.通过调节晶体对信号光和背景光的有效光伏系数之比r或信号光光强可以控制它的自偏转.还用数值方法研究了灰空间孤子的自偏转特性，发现灰孤子光束自偏转特性依赖于横向初速度v.当v>0时，灰孤子光束朝ξ>0的方向 关键词： 光伏空间暗孤子 光伏空间灰孤子 扩散效应 自偏转     

非相干耦合的亮和暗光伏空间孤子对的偏转特性

采用数值方法研究了在一个具有扩散效应的光伏光折变晶体中的非相干耦合的亮和暗光伏空间孤子对的偏转特性.结果表明,由于非相干相互作用,晶体中的一个亮孤子和一个暗孤子互相俘获,且两个孤子的中心沿着相同的轨迹移动.发现,当亮孤子的入射峰值强度不变时,通过调节暗孤子的入射背景强度可以控制亮孤子的偏转;当暗孤子的入射背景强度处于一个特殊值时,亮孤子的偏转被抑制,而当暗孤子的入射背景强度偏离这个特殊值时,亮孤子发生偏转.同样,当暗孤子的入射背景强度不变时,其偏转可以通过调节亮孤子的入射峰值强度来控制.