Wang Zuojia, Yao Kan, Chen Min, Chen Hongsheng, Liu Yongmin
Department of Mechanical and Industrial Engineering, Northeastern University, Boston, Massachusetts 02115, USA.
College of Information Science and Electronic Engineering, Zhejiang University, Hangzhou 310027, China.
Phys Rev Lett. 2016 Oct 7;117(15):157401. doi: 10.1103/PhysRevLett.117.157401. Epub 2016 Oct 6.
Swift electrons moving closely parallel to a periodic grating produce far-field radiation of light, which is known as the Smith-Purcell effect. In this letter, we demonstrate that designer Babinet metasurfaces composed of C-aperture resonators offer a powerful control over the polarization state of the Smith-Purcell emission, which can hardly be achieved via traditional gratings. By coupling the intrinsically nonradiative energy bound at the source current sheet to the out-of-plane electric dipole and in-plane magnetic dipole of the C-aperture resonator, we are able to excite cross-polarized light thanks to the bianisotropic nature of the metasurface. The polarization direction of the emitted light is aligned with the orientation of the C-aperture resonator. Furthermore, the efficiency of the Smith-Purcell emission from Babinet metasurfaces is significantly increased by 84%, in comparison with the case of conventional gratings. These findings not only open up a new way to manipulate the electron-beam-induced emission in the near-field region but also promise compact, tunable, and efficient light sources and particle detectors.
快速移动且与周期性光栅紧密平行的电子会产生光的远场辐射，这被称为史密斯 - 珀塞尔效应。在本信函中，我们证明了由C型孔径谐振器组成的定制巴比涅特超表面能够对史密斯 - 珀塞尔发射的偏振态进行有力控制，而这几乎无法通过传统光栅实现。通过将源电流片处固有的非辐射能量耦合到C型孔径谐振器的面外电偶极子和面内磁偶极子上，由于超表面的双各向异性，我们能够激发交叉偏振光。发射光的偏振方向与C型孔径谐振器的取向一致。此外，与传统光栅的情况相比，巴比涅特超表面的史密斯 - 珀塞尔发射效率显著提高了84%。这些发现不仅为在近场区域操纵电子束诱导发射开辟了一条新途径，还有望实现紧凑、可调谐且高效的光源和粒子探测器。
