微粒在结构矢量光场的横向光学操控研究

Shaping structured optical fields and engineering microparticles with different physical characteristics can significantly improve optical manipulations and give rise to some new applications. In this project, we will investigate the optical manipulation of microparticles with different optical properties illuminated by various elaborately designed vector optical fields, and, in particular, pay much more attention to the novel physical phenomena as well as the potential applications. Using the accurate full wave simulation and the dipolar and multipolar expansion approximations, we will reveal the underlying physics of these exotic phenomena. To be specific, our researches are going to concern the following aspects. (i) We will explore the new mechanism for inducing a transverse optical force. To this end, we propose to specially design a vector light field that can exert an enhanced transverse gradient optical force on microparticles with the size ranging from subwavelength to Rayleigh scale. (ii) We will examine the transverse optical force acting on dipolar particles illuminated by multiple plane waves, and focus on the anomalous lateral optical force perpendicular to the direction of light propagation as well as reveal its new physical origin based on the dipole approximation. (iii) We will derive the analytical expression of the optical fore on nonlinear particles in generic monochromatic pulsed light fields within the dipole approximation, and then exhibit the influence of nonlinear optical effects of different orders on the transverse optical force. The aforementioned works not only help for further understanding the novel phenomena in transverse optical manipulations of microparticles and their physical mechanisms, but also offer the theoretical reference for optical manipulations in the practical applications.

设计结构光场和构造不同物理性质的微粒可以有效改善光学操控并带来新的应用。本项目主要研究不同光学性质的微粒在各种结构矢量光场中的横向光学操控，着重探索新奇的物理现象及潜在的应用，并拟采用精确的全波模拟方法和偶极与多极展开近似理论揭示这些新现象的物理机制。具体来说，主要研究内容包括：（1）探索新的横向光力诱发机制，并基于此设计特别的结构光场，以增强尺寸在亚波长到Rayleigh尺度的微小粒子在光场中受到的横向梯度光力。（2）考察偶极粒子在多个平面波干涉场中的横向光力，着重研究在垂直于传播方向上的反常侧向光力，并揭示其新的物理机制。（3）基于偶极近似理论推导非线性微粒在任意单色脉冲光场中的光力解析表达式，并展示各阶非线性光学效应对横向光力的影响。本项目的研究有助于人们更加深入认识和理解微粒横向光学操控的新奇现象及其物理机制，同时为光学操控的实际应用提供理论依据。

基于光力的无接触光学操控已成为众多微粒操控手段中不可或缺的工具，而改善光学操控和拓展其应用的主要途径在于研究操控光场和被操控微粒。本项目主要研究不同物理性质的微粒在设计的结构矢量光场中的横向和纵向光学操控，重点考察了在操控中出现的新物理现象及可能的应用，并发展相应的解析理论和计算程序，以此揭示这些现象的物理机制，为实际的光学操控应用提供依据。研究内容主要包括：①建立计算任意尺寸微粒在任意单色光场中光学梯度力和散射力的理论体系，并通过设计不同的结构光场来调制Rayleigh到Mie尺寸范围的微粒受到的梯度力和散射力，以此实现对微粒的捕获、输运或筛选等。②研究任意尺寸的微粒在任意多个平面波形成的干涉光场中受到的反常侧向光力，以及偶极微粒对在平面波光场中的侧向光力及光学捆绑，并发展相关的解析理论以揭示其物理起源，同时提出相应的侧向操控理论方案。③考察非线性偶极微粒在任意单色脉冲光场中的光力，并分析微粒各阶非线性效应对光力的影响。④另外，还研究在光子晶体中激发的拓扑边缘态，该结构激发的表面光场有望用于长距离的微粒操控。这些研究结果不仅进一步丰富了光力的研究理论，而且为优化光学操控提供理论参考。