4pi聚焦系统中振幅和相位调制的径向偏振涡旋光束聚焦特性的研究

基于Richards-Wolf矢量衍射积分公式, 研究了径向偏振涡旋光束在振幅和相位调制下的4pi聚焦特性.振幅调制是通过振幅滤波实现, 即改变入射光束起始积分值达到调节,相位调制是通过添加相位延迟角δ 的液晶相位延迟器来改变入射光束的偏振态.模拟结果显示,随着振幅的减小, 4pi聚焦系统焦点附近的光轴上呈现出多光球结构; 而相位调制对焦点附近的光强分布产生拉伸作用, 即调节入射光束的拓扑核m和相位延迟器的延迟角δ,可以得到特殊的光强分布. 随着相位δ增大, m=0产生的多光球结构慢慢向光链结构转变,最终变成暗通道;而m=1产生的光链结构慢慢变成光球结构; m=2产生的暗通道变成光球和光链叠加的结构, 这种特殊聚焦光束在光学微操纵领域具有潜在的应用价值.关键词：物理光学偏振光链4pi聚焦系统

Study of the focusing features of spatial amplitude and phase modulated radially polarized vortex beams in a 4pi focusing system

The focusing properties of phase and amplitude modulated radially polarized vortex beams in a 4pi focusing system are theoretically investigated near the focal plane by using Richards-Wolf vectorial diffraction method. The amplitude modulation of vortex beams can be adjusted by changing the start integration value. The phase modulation of vortex beams can be realized by adding liquid crystal variable retarder with the phase delay angle δ. The simulated results show that multiple spherical spots can be obtained near the focus of the 4pi focusing system with the decrease of amplitude. The phase delay angle δ of the input beams can generate extruding effect for the electrical field distribution near the focus of the 4pi focusing system. Some special intensity distributions can be obtained by changing topological charge m and phase delay angle δ. Optical chain can be generated in the case of m=1. Dark channel can be obtained in the case of m=2. These special focusing beams can also transform with phase modulation. With the increase of phase δ, the multiple spherical spots at m=0 change slowly into an optical chain, and finally become a dark channel. In contrast, the optical chain at m=1 changes slowly into multiple spherical spots; and the dark channel at m=2 changes into the superposition of optical spherical spots and the optical chain. These special focusing beams have potential applications in optical trapping and micro-manipulation.
Keywords：physical opticspolarizationoptical chain4pi focusing system