Generating an optical needle with prescribed length and polarization direction through reversing the radiation pattern from a spatial ULS antenna
Yongxi Zeng, Musheng Chen, Han Huang, Pinghui Wu, Mianmian Zhou, Yanzhong Yu
Abstract
Unlike the conventional optical needle directed along the optical axis, we propose an approach to generate an optical needle with prescribed polarization direction and length by inversely focusing the radiation pattern from a spatial uniform line source (ULS) antenna in a 4Pi focusing system. The spatial ULS antenna situated at the foci of the 4Pi configuration is employed to obtain the required illumination at the pupil plane for creating the above optical needle through the use of a time-reversal holographic methodology. Numerical results show that the spatial polarization direction of the created optical needle is consistent with that of the spatial ULS antenna, that its length is approximately equal to the length of the ULS antenna, and that the transverse size of the optical needle is ∼0.36λ over its extent. The proposed method is more flexible than traditional methods for customizing the optical needle with prescribed characteristics.