1] Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA [2] Maryland Nano-Center, University of Maryland, College Park, Maryland 20742, USA.
Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
Nat Commun. 2014 Jun 17;5:4141. doi: 10.1038/ncomms5141.
Asymmetric electromagnetic transmission has been recently demonstrated using Lorentz-reciprocal devices, which exploit a variety of patterned structures of linear materials to break spatial inversion symmetry. However, nanofabrication challenges have so far precluded the fabrication of passive transmission structures with highly asymmetric responses at visible frequencies. Here we show that high-contrast asymmetric transmission of visible light can be provided by a planar device of wavelength-scale thickness incorporating a pair of nonsymmetric subwavelength gratings and a passive hyperbolic metamaterial engineered to display a transmission window centred at a lateral spatial frequency substantially exceeding the diffraction limit. Fabricated devices designed for operation at central wavelengths of 532 and 633 nm, respectively, display broadband, efficient asymmetric optical transmission with contrast ratios exceeding 14 dB. Owing to its planar configuration, small footprint and passive operation, this reciprocal transmission approach holds promise for integration within compact optical systems operating at visible frequencies.
最近，利用洛伦兹互易器件展示了非对称电磁传输，这些器件利用各种线性材料的图案结构来打破空间反转对称性。然而，纳米制造的挑战迄今为止阻止了在可见光频率下具有高度非对称响应的无源传输结构的制造。在这里，我们展示了一种基于平面器件的高对比度可见光非对称传输，该器件的厚度为波长量级，包含一对非对称亚波长光栅和一个被动超材料，设计用于显示中心位于横向空间频率的传输窗口，该频率大大超过衍射极限。分别为 532nm 和 633nm 中心波长设计的制造器件显示出宽带、高效的非对称光传输，对比度超过 14dB。由于其平面结构、小尺寸和无源操作，这种互易传输方法有望集成到在可见光频率下工作的紧凑光学系统中。
