光阱中的CaCO_3晶体微粒的光致旋转

Optical Rotation of Crystal CaCO_3 Micro-Particle in Optical Tweezers

从理论上分析了偏振光束与双折射晶体粒子的相互作用过程,讨论了由于光束自旋角动量向晶体粒子的传递所导致的光致旋转效应的原理,并在纳米光镊装置上利用线偏振He Ne激光器(633 nm,10 mW)形成了光镊光阱,利用1/4波片来改变光镊光束的偏振状态,在不同的椭圆偏振状态下实现了直径约为几微米的CaCO3 晶体微粒的捕获和光致转动.同时利用CCD相机和四像限探测器(QD)测量了粒子光致旋转的转动频率,研究了粒子的旋转频率随激光功率的变化关系.结合实验结果从理论上详细讨论了粒子自身的性质,如厚度、半径和晶体粒子的光轴取向等因素对粒子光致旋转转动速度与激光功率关系的影响.

In the paper the principle of optical rotation due to the transfer of spin angular momentum from light to particles was discussed by analyzing the interaction between the beam of light and birefringent crystal particles, and then an optical tweezers was formed on nanometer optical tweezers system with a linearly polarized light beam (He-Ne laser 633 nm, 10 mW). A quarter wavelength plate was used to change the polarization of light. The calcite particles (about several μm in diameters) were then trapped by the optical tweezers under different polarization of light. At the same time optical rotation of the particles was realized. The rotation frequency was measured by CCD camera and quadrant photodiode detector (QD). The dependence of the rotation frequency of the trapped particle on the laser-power was analyzed and experimentally studied for several calcite crystallites with different sizes in the optical tweezers. The effects of several particle parameters such as thickness, radius, and orientation of its optic axis etc. were also discussed.