光诱导光子晶格中基于涡旋光轨道角动量的光传输调控

All-optical networks provide a very promising platform to deal with the task, which is able to efficiently transmit and rapidly process huge amounts of data has become almost indispensable to our daily lives. Within such networks all-optical routing and switching, where light is directed by light, are a crucial building block for an effective operation. Nonlinear effects of weak-light, such as optically induced photonic lattices, that has been successfully realized within the bulk of photorefractive crystals, self-accelerating beams give the effective means that light is controlled by light, Optical waves propagation in linear and nonlinear periodic photonic structures exhibit behanvior characteristic of that encountered in discrete systems, which in many cases has no counterparts in homogeneous systems. We have meet challenge which light beam is not deflected with the azimuthal angle by optical signals for constricted by the maximum deflection angle in photorefractive crystals. According to our results about properties of light beam propagating in photonic lattices and recent references of vortex beam、orbital angular momentum, We predict there are the defect localized states in optically induced photonic lattices in photorefractive crystals, which combinations of vortex beam that carries phase singularity, and steering beams. The project will be doing：① We are going to investigate optical vortices propagation in 2D optically induced photonic lattices with photorefractive effect, the optical field obeys a saturable nonlinear Schrödinger equation and we experimentally observe it; ②The robustness and existence of the defect localized states of vortex solitons in 2D optically induced photonic lattices with photorefractive effect, phase singularity of vortex beam and orbital angular momentum is going also studied experimentally; ③We will experimentally and theoretically study the light propagation in 2D optically induced photonic lattices using the beam propagation method, We is going to explore relationship of shape and tunable defect localized state and deflection of optical signals, We want to discover how to control the optical signals by means of changing shape and strengh of defect localized state。Possible breakthrough：We predict there is controlled defect localized state of vortex soliton; We will realize that optical signals is controlled by defect localized state and orbital angular momentum of vortex beams; The project open new field of research which vortex beam propagation in photonic lattice is dominated by discrete effect, nonlinearity and its orbital angular momentum. Many new phenomana and effects are expected. These distinct features of discreteness can be exploited for potentially important application in all-optical signal data processing, optical communication systems, switching networks and orbital angular momentum multiplex.

光控光是实现光交换网络、光开关之关键问题。近年来弱光非线性理论的发展为实现光控光提供了有效手段，本项目组前期的研究发现光诱导光子晶格对光信号的任意偏转调节控制问题尚待解决。结合前期研究基础、涡旋光轨道角动量及自加速光束研究进展，我们预测：光诱导的光子晶格、涡旋光轨道角动量及自加速光束共同作用会形成光子晶格中的缺陷局域态并实现对光束的调控。本项目拟开展：①采用非线性薛定谔方程和实验研究涡旋光轨道角动量变化对其在光诱导的缺陷光子晶格中的传播行为；②研究涡旋光轨道角动量变化在光子晶格中形成涡旋孤子缺陷局域态的影响条件；③采用光束传播法研究光束在离散光子晶格、涡旋阵列晶格中的传播，探索涡旋孤子缺陷局域态深度、形状等对光束的控制条件。可能的突破：发现稳定、可控的光诱导光子晶格缺陷局域态；利用涡旋光角动量、光子晶格缺陷态控制光束的路径。本项目为光子晶格在光交换网络、光轨道角动量复用等方面的奠定了基础。

研究了空间尺寸缩放的四方晶格中的一阶涡旋离散孤子的存在性和稳定性。在矩形晶格中，由于晶格空间尺寸缩放的不对称性，涡旋孤子出现了强度分布的不对称，同时涡旋孤子特有的相位结构被破坏。菱形晶格中的孤子可以很好的保持涡旋的相位结构，每个相邻主峰之间的相位差仍然保持π/2。对孤子解的稳定性分析得到的结果是，低能量的孤子在矩形晶格中解呈现指数型不稳定；在菱形晶格中虽然同时表现出震荡不稳定和指数不稳定，但是不稳定模式的增长率比矩形晶格中小一个数量级。研究了中心对称光折变介质中具有单个缺陷的正方形光子晶格中的缺陷带隙孤子。研究发现对于正缺陷，缺陷孤子存在于半无穷带隙中，并且在低功率范围内是稳定。正缺陷孤子随缺陷强度的增加，存在和稳定的范围都会变窄。对于负缺陷，缺陷孤子可以同时存在于半无穷带隙和第一带隙中。在缺陷强度适中的情况下，半无穷带隙中的缺陷孤子在适当功率范围稳定。研究了二维艾里光束在自聚焦饱和非线性介质中的传输。在不存在光子晶格的自聚焦非线性介质中，发现二维艾里光束的主瓣能量发生会聚现象，传输距离增加，艾里光束原有的强度分布被破坏。在Lieb光子晶格中传输时，固定晶格强度，艾里光束的主瓣格点入射到Lieb光子晶格中，对于合适的外偏压，艾里光束的自加速停滞，形成一种稳定态，光束的整体尺寸减小，能流密度朝向主瓣初始入射的方向，能量得到会聚。研究了在自聚焦非线性单格点激励条件下二阶涡旋光与异相四极光束的相互转化。在合适的自聚焦非线性条件下二阶涡旋光会自陷形成周期性的旋转准涡旋孤子，以异相四极状光束作为过渡态来翻转拓扑电荷和旋转方向；对于异相四极光束来说，入射取向沿着晶格光轴方向或者对角轴方向的异相四极光束可以通过单格点激励自陷形成一个四极孤子，当改变相对于晶格光轴的初始角度后则会产生周期性振荡现象，在传播过程中会变为旋转的二阶涡旋孤子，并在旋转方向相反时经历拓扑电荷翻转。实现了对光的控制。