Weng, Xiaoyu, Guo, Hanming, Sui, Guorong, Hu, Qi, Zheng, Jihong, Wang, Yang, and Zhuang, Songlin
Abstract: Vectorial properties of light have significant effects on the focusing properties, especially for the case of tightly focusing, where the requirements on the ratio of the longitudinal field to the traverse fields (RLT) are different for various applications, such as particle acceleration, micronano-fabrication, fluorescent imaging, determination of three dimensional orientation of individual molecules and so on. Here, utilizing inhomogeneous polarization modulation (IPM) method, we demonstrate how to adjust the numbers of focal spots, the RLT, and the depth of focus (DOF) in terms of requirements and create successfully single or multiple focal spots with dominant transverse or longitudinal fields and small size. In terms of this method, not only the asymmetry of the focal spot for linearly polarized illumination with IPM can be obviously decreased, but also its size is the same as that of the short axis of the elliptical focusing spot for the case without IPM. Moreover, it can not only produce the focal spot with dominant transverse field, low sidelobe, and size slightly smaller than that of the radial polarization, but also can realize the identical resolutions in the transverse direction. In addition, for a focal spot with dominant transverse or longitudinal field, both the subdiffraction sizes (0.4λ or 0.5λ) and the DOF of 6.92λ are also achieved. [Copyright &y& Elsevier]