非线性周期结构中的离散光涡旋现象研究

Optical vortex beams are intriguing special optical structures with helical wave fronts, which attract much attention for their well-defined orbital angular momentum properties. This kind of special optical field has been applied widely in many fields that include optical micromanipulation，optical microscopy, optical information processing and nonlinear optics.The propagation dynamics of optical vortices in continuous bulk media has been well understood. However, people know little about the properties of optical vortices in periodic structures which limits the application of optical vortices in discrete systems. This project tends to fill the gap and expand the study of optical vortices from bulk materials to periodic media. We will study the discretizing light behaviors of optical vortices inside and at the surface of both linear and nonlinear 2D optically induced lattices in photorefractive crystals and explore the relationship between the topological charge of the optical vortices and the bandgap structures, the generation of the discrete vortices from the Bloch modes, the interaction between discrete vortex solitons and the propagation dynamics of the vortex beam in the defective lattices and at the boundary of photonic lattices. We want to reveal the law of the interaction between the angular momentum of the optical vortices, the bandgap structures of photonic lattices and the nonlinearity. Furthermore, we will realize a variety of novel discrete vortex states, defect vortex states , discrete surface vortex states and related discrete vortex phenomena in optical periodic structures. Our study not only provides the possibility of manipulation of the orbital angular momentum in periodic structures, but also has a direct impact on similar discrete vortex phenomenona in other nonlinear periodic systems beyond optics.

涡旋光是一种具有轨道角动量的特殊光场，它在光学微操纵、光学显微、光信息传输、非线性光学等领域得到了广泛的应用。目前，人们对涡旋光的研究主要集中在连续介质中，对于涡旋在光学周期结构中的传播规律还不是很清楚，这就限制涡旋光在周期结构中的应用。本项目拟将涡旋光的研究从连续介质拓展到光学周期结构中，研究涡旋光在光学诱导法制备的二维光子晶格中的线性与非线性离散传播行为，阐明涡旋光的拓扑电荷与带隙结构的关系；光子晶格的布洛赫模式与离散涡旋的关系；离散涡旋孤子之间相互作用以及涡旋光与光子晶格中缺陷及晶格表面相互作用的规律。从而揭示由于涡旋光的轨道角动量、光子带隙结构及非线性相互作用的新规律。实现多种新颖的离散涡旋孤子态、缺陷涡旋态及离散表面涡旋态。我们的研究不仅为在周期结构中操控轨道角动量提供了可能，而且能为其它非线性周期系统中的离散涡旋现象提供有益的借鉴。

涡旋是一种普遍存在的物理现象，从宏观的宇宙星系、到微观的超流、超导量子体系中都存在涡旋。在光学领域的光涡旋由于具有轨道角动量特性，在光操纵、光通信及成像等方面的应用引起了人们极大的兴趣。通常关于涡旋光的研究都是在连续介质中。本项目主要研究周期结构中的光涡旋现象，揭示光学周期结构中的离散光涡旋的新物理与新现象。在项目执行期间，我们重点研究了光诱导方法制备的蜂巢型光子晶格和四方光子晶格中的离散涡旋现象。我们实现了与子晶格自由度相关的整数涡旋和分数涡旋的可控产生，揭示了蜂巢型光子晶格中赝自旋与涡旋角动量的关系；发现了高带非线性涡旋模式与四极光模式的相互作用及周期性转化现象，此外我们还实现了复杂光子晶格中的平带模式及图像传输。我们的研究不仅为在周期结构中操控轨道角动量提供了可能，而且能为其它非线性周期系统中的离散涡旋现象提供有益的借鉴。相关结果发表在了Nature Communications、Optics Letters、Optical Express、2D materials等国际学术期刊上。