二元凝聚体中亮-亮孤子的振荡-局域转变行为

考虑时间相关的种间相互吸引作用,研究了局限于谐振外部势阱中的二元玻色-爱因斯坦凝聚体中亮-亮孤子的传播特性.结果表明,当种内和种间相互吸引作用都不变时,亮-亮孤子呈现出周期性的振荡;如果种内相互吸引作用仍保持不变,而种间相互吸引作用随时间指数增加时,发现凝聚体中产生振荡-局域转变行为,且这种振荡-局域的转变行为可通过调节谐振势阱的横向囚禁频率来控制.此外,还设计了实验方案来观察孤子的这种振荡-局域转变行为.     

深光晶格势阱中凝聚体的扭结包络隙孤子

发展准离散多尺度法结合紧束缚近似,解析地研究了局陷于光晶格势阱中凝聚体的非线性动力学性质.结果发现,系统中出现稳定的对称包络孤子外,还可观察到一种新的非线性元激发:扭结包络隙孤子.有趣的是,该隙孤子并不传播且局域在初始位置,其幅度可通过光晶格势阱的晶格常数和势阱深度来调控.相应的实验方案是:通过改变形成光晶格势阱的两交叉耦合激光束之间的夹角和(或)激光光强来调控扭结包络隙孤子的幅度.     

二元玻色-爱因斯坦凝聚体中矢量孤子的转化行为

考虑种内和种间相互作用均为排斥作用,研究了局限于谐振外部势阱中的二元玻色-爱因斯坦凝聚体中灰-灰和黑-黑孤子的动力学行为.结果表明:当谐振势阱的轴向囚禁频率为零时,灰-灰和黑-黑孤子均能保持局域稳定;而当轴向囚禁频率不为零时,凝聚体中的原子向势阱中心聚集,发现灰-灰孤子可以转化成亮-亮孤子.     

高斯势垒/阱作用下非局域矢量光孤子 的传输特性

非局域非线性介质中高斯势垒或势阱作用下矢量光孤子的传输特性,由具有高斯型线性势的耦合非局域非线性薛定谔方程描述,通过平方算子法对方程进行数值计算,并利用分步法仿真矢量光孤子的传输.在非局域非线性大块介质中,异相位矢量孤子的分量总是自发地分离,高斯势垒可以抑制分量间的排斥作用;同相位矢量孤子的分量则总是自发地融合,高斯势阱可以抑制分量间的吸引作用.通过定量分析势垒高度(或势阱深度)或宽度与矢量孤子两个分量在归一化传输距离为500处的间距之间的关系,发现如果势垒(或势阱)的高度(或深度)及宽度太大或太小,高斯线性势都不能抑制这一过程,甚至会恶化矢量光孤子的传输.对于异相位孤子,最有效抑制分量分离过程的高斯势垒设置是高度为1.10,宽度为1.00;对于同相位孤子,最有效抑制分量融合过程的高斯势阱应设置是深度为-1.50,宽度为1.00.研究结果可为全光开关、光逻辑门、光计算等光控光技术提供参考.     

强非局域光晶格中空间孤子的脉动传播

根据强非局域结构中空间孤子的演化方程——非局域非线性薛定谔方程,采用分步傅里叶方法,对一维强非局域光晶格结构中空间孤子的脉动传播进行数值研究.分析了孤子的初始光束能量、非局域程度、光晶格调制强度、光晶格周期以及线性折射率的纵向调制率与空间孤子的脉动传播周期之间的关系,并对影响脉动传播的内在物理机制进行了讨论.同时,还研究了在线性折射率纵向调制情况下强非局域光晶格结构中空间孤子传输的开关行为. 关键词： 非局域非线性薛定谔方程 光晶格 空间孤子 光开关     

玻色-爱因斯坦凝聚体中的双孤子相互作用操控

考虑周期性驱动线性势, 利用Darboux变换法解析地研究了玻色-爱因斯坦凝聚体(BEC)中的双孤子相互作用, 得到了S-波散射长度的临界值. 结果表明: 当S-波散射长度高于临界值时, BEC中的两个亮孤子相互吸引并融合; 而当S-波散射长度低于临界值时, 两个亮孤子保持局域稳定. 此外, 在外部势阱的驱动下, 两个稳定的亮孤子产生周期性振荡行为.     

亮-暗复色光伏孤子

提出一种实现亮-暗复色光伏孤子的方法.不共轴的两束同频率相干但反相的亮光束共同形成一中空光束，在此暗区引入另一束不同频率的亮光束.这三束光在一定条件下可以通过非线性相互作用而形成亮-暗复色孤子.通过数值分析的方法对这种亮-暗复色光伏孤子的空间动力过程进行了研究.研究表明，这种亮-暗结构具有光控光特性. 关键词： 亮-暗复色光伏空间孤子 光控光     

方势阱中凝聚体的孤子动力学行为

利用多重尺度法, 解析地研究了方势阱中玻色-爱因斯坦凝聚体的孤子动力学行为. 结果表明, 方势阱对凝聚体中的孤子动力学有重要的影响. 进入方势阱时孤子作加速运动, 逃逸出势阱时孤子作减速运动; 且随着势阱深度的增加, 孤子的速度增加、幅度增加、宽度减小. 这为实验操控孤子的动力学行为提供一定的参考价值. 关键词： 玻色-爱因斯坦凝聚体 孤子 方势阱     

背景光光伏效应对屏蔽-光伏空间孤子的影响

在光伏晶体两端外加一恒定的直流偏压，背景光的光伏效应对形成屏蔽-光伏孤子的空间电荷场没有影响，但对晶体中的电流有影响.如果外电源的电动势是恒定的，则背景光的光伏效应与外电路的电阻协同起作用，可以通过晶体两端的电压降影响晶体中的空间电荷场，进而影响空间孤子的宽度.在一定的条件下甚至可以实现亮、暗孤子的转换. 关键词： 屏蔽-光伏 空间孤子 孤子宽度 亮暗孤子转换     

非局域非线性耦合器中多极亮孤子的特性

研究了一维非局域非线性耦合器中多极亮孤子的存在条件和稳定传输.用牛顿迭代法得到了二极和三极亮孤子.由于较强的非局域响应诱导孤子间的吸引作用比排斥作用大,此时二极孤子不能稳定传输,两孤子相互吸引,融合成一个孤子.随着非局域参数的减小,非线性效应和衍射效应达到平衡时,二极孤子能稳定传播.随着传播常数的减小,孤子的幅值减小,束宽变窄,使得孤子能稳定传播.对于三极亮孤子,在非局域参数较小的时候,耦合的两个三极孤子都不能进行稳定传输.传输一段距离后三极孤子发生碰撞,融合成两极孤子,两极孤子继续传输,最终融合成为一束振荡的光束.随着非局域参数的增大,三极孤子传播的稳定性增强.当传播常数取负数时,随着其绝对值的减小,三极亮孤子的幅值增大,束宽减小,孤子传播的稳定性增强.最后,通过加入白噪声进一步验证了这些亮孤子传播稳定性.     

Reflection-Transmission Transition of Bright-Bright Solitons Collision in Two Species Condensates with Repulsive Interspecies Interactions

Considering repulsive interspecies interactions,we study the dynamical properties of bright-bright solitons in two species Bose-Einstein condensates by using a variational approach combined with numerical simulation.It is shown that the interactions between bright-bright solitons vary from repulsive to attractive interactions with the increasing their separating distances,and at equilibrium position the bright-bright solitons are localized.Interestingly,a transition from reflection-to transmission-collision is firstly observed,different from previous results of only reflection collision appearing there.These results will be helpful for the experimental manipulating such solitons.     

Reflection-Transmission Transition of Bright-Bright Solitons Collision in Two Species Condensates with Repulsive Interspecies Interactions

Considering repulsive interspecies interactions, we study the dynamical properties of bright-bright solitons in two species Bose-Einstein condensates by using a variational approach combined with numerical simulation. It is shown that the interactions between bright-bright solitons vary from repulsive to attractive interactions with the increasing their separating distances, and at equilibrium position the bright-bright solitons are localized. Interestingly, a transition from reflection- to transmission-collision is firstly observed, different from previous results of only reflection collision appearing there. These results will be helpful for the experimental manipulating such solitons.     

Asymmetric vortex solitons in nonlinear periodic lattices

We reveal the existence of asymmetric vortex solitons in ideally symmetric periodic lattices and show how such nonlinear localized structures describing elementary circular flows can be analyzed systematically using the energy-balance relations. We present the examples of rhomboid, rectangular, and triangular vortex solitons on a square lattice and also describe novel coherent states where the populations of clockwise and anticlockwise vortex modes change periodically due to a nonlinearity-induced momentum exchange through the lattice. Asymmetric vortex solitons are expected to exist in different nonlinear lattice systems, including optically induced photonic lattices, nonlinear photonic crystals, and Bose-Einstein condensates in optical lattices.     

Dynamic stability and manipulation of bright matter-wave solitons by optical lattices in Bose-Einstein condensates

An extended variation approach to describing the dynamic evolution of self-attractive Bose-Einstein condensates is developed. We consider bright matter-wave solitons in the presence of a parabolic magnetic potential and a time-space periodic optical lattice. The dynamics of condensates is shown to be well approximated by four coupled nonlinear differential equations. A noteworthy feature is that the extended variation approach gives a critical strength ratio to support multiple stable lattice sites for the condensate. We further examine the existence of the solitons and their stabilities at the multiple stable lattice sites. In this case, the analytical predictions of Bose-Einstein condensates variational dynamics are found to be in good agreement with numerical simulations. We then find a stable region for successful manipulating matter-wave solitons without collapse, which are dragged from an initial stationary to a prescribed position by a moving periodic optical lattice.     

Combined periodic wave and solitary wave solutions in two-component Boseben Einstein condensates

In this paper, the Jacobi elliptic function expansion method provides an effective approach to obtain the exact periodic wave solutions of two-component Bose-Einstein condensates. Exact combined bright-bright and dark-dark soliton wave solutions can be achieved in their limit conditions. We also obtain the different formation regions of combined solitons. Our results show that the intraspecies (interspecies) interaction strengths clearly affect the formation of dark-dark, bright-bright and dark-bright soliton solutions in different regions.     

Superposition solitons in two-component Bose-Einstein condensates

We develop the Hirota bilinear method and obtain the exact one and two superposition soliton solutions for two-component Bose-Einstein condensates. The conversion of three kinds of solitons including the superposition solitons, bright-bright solitons, and dark-bright solitons is discussed. With the energy analysis, we find that the superposition soliton state is an excitation state for this system. Moreover, the collision of two superposition solitons is found to be elastic.     

Ground states, solitons and spin textures in spin-1 Bose-Einstein condensates

We present an overview of our recent theoretical studies on the quantum phenomena of the spin-1 Bose-Einstein condensates, including the phase diagram, soliton solutions and the formation of the topological spin textures. A brief exploration of the effects of spin-orbit coupling on the ground-state properties is given. We put forward proposals by using the transmission spectra of an optical cavity to probe the quantum ground states: the ferromagnetic and polar phases. Quasi-one-dimension solitons and ring dark solitons are studied. It is predicted that characteristics of the magnetic solitons in optical lattice can be tuned by controlling the long-range light-induced and static magnetic dipoledipole interactions; solutions of single-component magnetic and single-, two-, three-components polar solitons are found; ring dark solitons in spin-1 condensates are predicted to live longer lifetimes than that in their scalar counterparts. In the formation of spin textures, we have considered the theoretical model of a rapidly quenched and fast rotating trapped spin-1 Bose-Einstein condensate, whose dynamics can be studied by solving the stochastic projected Gross-Pitaevskii equations. Spontaneous generation of nontrivial topological defects, such as the hexagonal lattice skyrmions and square lattice of half-quantized vortices was predicted. In particular, crystallization of merons (half skyrmions) can be generated in the presence of spin-orbit coupling.     

Tunable ground-state solitons in spin–orbit coupling Bose–Einstein condensates in the presence of optical lattices

Properties of the ground-state solitons, which exist in the spin–orbit coupling(SOC) Bose–Einstein condensates(BEC) in the presence of optical lattices, are presented. Results show that several system parameters, such as SOC strength,lattice depth, and lattice frequency, have important influences on properties of ground state solitons in SOC BEC. By controlling these parameters, structure and spin polarization of the ground-state solitons can be effectively tuned, so manipulation of atoms may be realized.     

Matter-Wave Solitons in Two-Component Bose-Einstein Condensates with Tunable Interactions and Time Varying Potential

We present three families of exact matter-wave soliton solutions for an effective one-dimension two-component Bose-Einstein condensates (BECs) with tunable interactions, harmonic potential and gain or loss term.We investigate the dynamics of bright-bright solitons, bright-dark solitons
and dark-dark solitons for the time-dependent expulsive harmonic trap potential,periodically modulated harmonic trap potential, and kinklike modulated harmonic trap potential.Through the Feshbach resonance, these dynamics can be realized in experiments by suitable control of time-dependent trap parameters, atomic interactions, and interaction with thermal cloud.