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 $\sim 0.36\lambda$ over its extent. The proposed method is more flexible than traditional methods for customizing the optical needle with prescribed characteristics.

与沿光轴定向的传统光针不同，我们提出了一种方法，通过在 4Pi 聚焦系统中反向聚焦来自空间均匀线源 (ULS) 天线的辐射方向图，生成具有指定偏振方向和长度的光针。位于 4Pi 配置焦点处的空间 ULS 天线用于通过使用时间反转全息方法在光瞳平面获得所需的照明，以创建上述光学针。数值结果表明，所创建的光针的空间极化方向与空间ULS天线的空间极化方向一致，其长度近似等于ULS天线的长度，光针的横向尺寸为$～0.36\lambda$超过其范围。所提出的方法比定制具有规定特性的光学针的传统方法更灵活。