影响空间变化偏振矢量光束强聚焦后焦斑移位的因素

利用衍射积分公式数值模拟了不同阶次的空间变化偏振矢量贝塞尔高斯(BG)光束经过强聚焦系统后在焦点附近的强度分布。数值结果显示空间变化偏振矢量BG光束聚焦后在光束传播轴负方向存在焦斑移位现象,其焦斑移位的大小与光束的模阶次、光束宽度、波长以及局部偏振状态密切相关。矢量光束偏振态的变化依靠液晶相位延迟器(LCVR)的相位延迟角度来控制,由于LCVR的相位延迟角度可以在0～π之间连续变化,从而改变光束的局部偏振状态,间接实现了对矢量光束焦斑移位大小的实时控制,在光学微操纵领域具有潜在的应用价值。

Effect Factors of the Focal Shift in Spatial-Variant Polarized Vector Beams

The intensity distribution of focused spatial-variant polarized Bessel-Gauss vector beams is numerically simulated in the vicinity of the focal plane by using Richards-Wolf vectorial diffraction method. The existence of the focal shift in the negative direction of propagation is proved. The magnitude of the focal shift is closely associated with the order number of beam, beam width, wavelength and local polarization. The polarized state can be changed by adjusting the phase delay angle of the liquid crystal variable retarder, which can be continuously varied from 0 to π. The controllability of the focal shift in real time aroused by the phase delay angle will have great potential applications in optical micro-manipulations.