Zhu Yechuan, Yuan Weizheng, Li Wenli, Sun Hao, Qi Kunlun, Yu Yiting
Opt Lett. 2018 Jan 15;43(2):206-209. doi: 10.1364/OL.43.000206.
Slit arrays based on noble metals have been widely proposed as planar transverse-magnetic (TM)-lenses, illuminated by a linearly polarized light with the polarization perpendicular to slits and implementing the focusing capability beyond the diffraction limit. However, due to intrinsic plasmonic losses, these TM-lenses cannot work efficiently in the ultraviolet wavelengths. In this Letter, taking advantage of the unique transmission through metallic slits not involving plasmonic losses, a metallic slit array with transverse-electric (TE)-polarized design is proposed, showing for the first time, to the best of our knowledge, the realization of sub-diffraction-limit focusing for ultraviolet light. Additionally, in contrast to the situations of TM-lenses, a wider slit leads to a greater phase delay and much larger slits can be arranged to construct the TE-lenses, which is quite beneficial for practical fabrication. Furthermore, deep-subwavelength focusing can be achieved by utilizing the immersing technology.
基于贵金属的狭缝阵列已被广泛提议用作平面横向磁（TM）透镜，由偏振垂直于狭缝的线偏振光照射，并实现超越衍射极限的聚焦能力。然而，由于固有等离子体损耗，这些TM透镜在紫外波长下无法高效工作。在本信函中，利用通过金属狭缝的独特传输（不涉及等离子体损耗），提出了一种具有横向电（TE）偏振设计的金属狭缝阵列，据我们所知，首次实现了紫外光的亚衍射极限聚焦。此外，与TM透镜的情况相比，更宽的狭缝会导致更大的相位延迟，并且可以安排更大的狭缝来构建TE透镜，这对实际制造非常有利。此外，利用浸没技术可以实现深亚波长聚焦。
