以飞秒激光器为光源, 搭建记录测量聚焦光斑的光学实验系统, 研究飞秒径向偏振光紧聚焦特性.数值模拟表明当物镜数值孔径为0.9, 波长为750 nm时, 线偏振光和径向偏振光焦斑的最小半高全宽分别是1.3 μm和1.0 μm.实验中, 使用全息干板作为记录介质, 记录和测量微小的聚焦光斑, 并通过精密电动平移台实现几十纳米量级步长的移动, 获得精确焦平面处的聚焦光斑.测量结果表明, 线偏振光和径向偏振光焦斑的最小半高全宽分别是4.6 μm和2.9 μm.在高数值孔径聚焦条件下, 径向偏振光可以获得比线偏振光更细锐的聚焦光斑.

The tight focusing properties of the femtosecond radially polarized light was analyzed on experimental setup, which including a femtosecond laser source and focal spot recording setup. According to the numerical simulation, in the case of being focused with the objective lens of NA=0.9, the linearly polarized light with the wavelength of 750 nm can get its smallest focal spot with FWHM of 1.3 μm, while that of the radially polarized light is 1.0 μm. The holographic plates were used as the recording media to record and measure the tiny focal spots, which were placed on a electric power-driven precise translation stage with precision of tens of nonameters so as to obtain the exactly minimum focal spots for the measurements by precise step-scan. The measurement result indicated that the radially polarized light can achieve sharper and tinier focal spots than the lineraly polarized light when with high NA focussing lens, whose FWHMs are 4.6 μm and 2.9 μm respectively for the same cases as the somulations.