Gao Xiaoqing, Zhai Cong, Lin Zuzeng, Chen Yulu, Li Hongbin, Hu Chunguang
State Key Laboratory of Precision Measuring Technology and Instruments, School of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin 300072, China.
Department of Chemistry, University of British Columbia, Vancouver, BC V6T 1Z1, Canada.
Micromachines (Basel). 2022 Apr 13;13(4):608. doi: 10.3390/mi13040608.
The highly focused laser beam is capable of confining micro-sized particle in its focus. This is widely known as optical trapping. The Janus particle is composed of two hemispheres with different refractive indexes. In a linearly polarized optical trap, the Janus particle tends to align itself to an orientation where the interface of the two hemispheres is parallel to the laser propagation as well as the polarization direction. This enables a controllable approach that rotates the trapped particle with fine accuracy and could be used in partial measurement. However, due to the complexity of the interaction of the optical field and refractive index distribution, the trapping trajectory of the Janus particle in the linearly polarized optical trap is still uncovered. In this paper, we focus on the dynamic trapping process and the steady position and orientation of the Janus particle in the optical trap from both simulation and experimental aspects. The trapping process recorded by a high speed camera coincides with the simulation result calculated using the -matrix model, which not only reveals the trapping trajectory, but also provides a practical simulation solution for more complicated structures and trapping motions.
高度聚焦的激光束能够将微米级粒子限制在其焦点处。这被广泛称为光学捕获。Janus粒子由两个具有不同折射率的半球组成。在线偏振光阱中，Janus粒子倾向于使其自身排列成两个半球的界面与激光传播方向以及偏振方向平行的取向。这实现了一种可控方法，能够以高精度旋转被捕获的粒子，并且可用于局部测量。然而，由于光场与折射率分布相互作用的复杂性，Janus粒子在线偏振光阱中的捕获轨迹仍未被揭示。在本文中，我们从模拟和实验两个方面关注Janus粒子在光阱中的动态捕获过程以及稳定位置和取向。高速摄像机记录的捕获过程与使用矩阵模型计算的模拟结果一致，这不仅揭示了捕获轨迹，还为更复杂的结构和捕获运动提供了一种实用的模拟解决方案。
