Wavevector Selective Metasurfaces and Tunnel Vision Filters

A multifunctional metasurface: from extraordinary optical transmission to extraordinary optical diffraction in a single structure

We show that, a metasurface composed of subwavelength metallic slit array embedded in an asymmetric environment can exhibit either extraordinary optical transmission (EOT) or extraordinary optical diffraction (EOD). By employing an analytical model expansion method and the diffraction order chart in k-vector space, we found that the resonance decaying pathway of the local slit cavity mode can be tuned to either 0th or -1st diffraction order by changing the parallel wavevector, which gives rise to enhanced 0th transmission (EOT) of the structure for small incident angles, and enhanced -1st diff…

Tailoring accidental double bound states in the continuum in all-dielectric metasurfaces

Bound states in the continuum (BICs) have been thoroughly investigated due to their formally divergent Q-factor, especially those emerging in all-dielectric, nanostructured metasurfaces from symmetry protection at the $Γ$ point (in-plane wavevector $k_{||}=0$). Less attention has been paid to accidental BICs that may appear at any other $k_{||}\not =0$ in the band structure of supported modes, being in turn difficult to predict. Here we make use of a coupled electric/magnetic dipole model to determine analytical conditions for the emergence of accidental BICs, valid for any planar array of met…

Asymmetric surface wave excitation through metasurface-edge diffraction

The selective excitation of localized surface wave modes remains a challenge in the design of both leaky-wave and bound-wave devices. In this Letter, we show how the truncation of a metasurface can play an important role in breaking the spatial inversion symmetry in the excitation of surface waves supported by the structure. This is done by combining a large anisotropy in the dispersion relation and the presence of an edge which also serves as a coupling mechanism between the plane wave excitation and the induced surface waves. By resorting to the exact solution of the scattering problem based…

调控共振超表面中的 Friedrich-Wintgen 干涉：按需倾斜角发射的涡旋激光

Taming Friedrich-Wintgen interference in resonant metasurface: vortex laser emitting at on-demand tilted-angle

提出并实验验证在光学超表面中按需调控 FW-BIC 偏振奇点，并基于钙钛矿实现斜角高定向、动量空间偏振涡旋激光。

脉冲驱动的光子跃迁与时空调制超材料中的非互易性

Pulse-driven photonic transitions and nonreciprocity in space-time modulated metasurfaces

本研究通过单周期超快脉冲调制实现光子跃迁，消除持续调制需求，展示自由空间波的强非互易性，拓展超快光学技术应用。

Fourier plane optical microscopy and spectroscopy

Intensity, wavevector, phase, and polarization are the most important parameters of any light beam. Understanding the wavevector distribution has emerged as a very important problem in recent days, especially at nanoscale. It provides unique information about the light-matter interaction. Back focal plane or Fourier plane imaging and spectroscopy techniques help to measure wavevector distribution not only from single molecules and single nanostructures but also from metasurfaces and metamaterials. This review provides a birds-eye view on the technique of back focal imaging and spectroscopy, di…