用旋转多普勒方法解析矢量涡旋光的偏振特征

Recognition of polarization rotation in vector vortex beam enabled by rotational Doppler effect

矢量涡旋光在光学微操控和光通信领域均具有独特优势。旋转多普勒效应常应用于涡旋光拓扑荷的研究,分析矢量涡旋光的旋转多普勒效应可以有效导出其丰富的偏振性质。提出了一种基于旋转多普勒效应分辨矢量涡旋光偏振旋转方向的方法,对应于矢量涡旋光符号的识别。在所提出方法中,矢量光经过旋转物体散射,散射光由于多普勒效应,各组分之间产生强度随时间周期性变化的拍频信号。拍频信号变化函数的相位取决于矢量涡旋在高阶庞加莱球上的代表点的赤道角,相位变化率取决于涡旋光拓扑荷。本工作提出测量理论并通过实验验证了涡旋方向相反的两种矢量光的拍频信号,为矢量涡旋光拓扑荷的符号测量提供了一种新的可行方法。

Vectorial vortex beam possesses unique advantages in the fields of micro optical manipulation and optical communication. Rotational Doppler effect is usually applied in the researches of topological charges of optical vortex, and analysis of rotational Doppler effect of vectorial vortex beam is meaningful to deduce properties of polarization. Here a method to discriminate the direction of rotation of cylindrical vector beams is proposed based on rotational Doppler effect. In the method, the scattered light of an incident vectorial vortex beam carries beating signal whose intensity changes periodically with time due to Doppler frequency shift. The phase of the beating signal variation function depends on equator angle of vectorial vortex on high-order Poincaré sphere and the slope of the function depends on topological charge of optical vortex. The measurement theory of beating signals of two vectorial vortex beams with opposite handnesses are proposed and experimentally verified, which provides a new effective method to measure the signs of topological charges of cylindrical vector beams.