Department of Applied Physics, Northwestern Polytechnical University, Xi'an, 710129, China.
Department of Physics, University of South Florida, 4202 East Fowler Ave, Tampa, FL, 33620-5700, USA.
Sci Rep. 2017 Sep 6;7(1):10730. doi: 10.1038/s41598-017-11242-9.
Because of the strong inherent resonances, the giant optical activity obtained via chiral metamaterials generally suffers from high dispersion, which has been a big stumbling block to broadband applications. In this paper, we propose a type of planar chiral metamaterial consisting of interconnected metal helix slat structures with four-fold symmetry, which exhibits nonresonant Drude-like response and can therefore avoid the highly dispersive optical activity resulting from resonances. It shows that the well-designed chiral metamaterial can achieve nondispersive and pure optical activity with high transmittance in a broadband frequency range. And the optical activity of multi-layer chiral metamaterials is proportional to the layer numbers of single-layer chiral metamaterial. Most remarkably, the broadband behaviors of nondispersive optical activity and high transmission are insensitive to the incident angles of electromagnetic waves and permittivity of dielectric substrate, thereby enabling more flexibility in polarization manipulation.
由于强烈的固有共振，通过手性超材料获得的巨大旋光性通常具有较高的色散性，这一直是宽带应用的一大障碍。在本文中，我们提出了一种由具有四重对称的互连金属螺旋板结构组成的平面手性超材料，其表现出非共振 Drude 响应，因此可以避免由于共振引起的高度色散的旋光性。结果表明，精心设计的手性超材料可以在宽带频率范围内实现无分散和纯旋光性以及高透过率。多层手性超材料的旋光性与单层手性超材料的层数成正比。最显著的是，无分散旋光性和高透射率的宽带行为对电磁波的入射角和介电基底的介电常数不敏感，从而在手性的偏振控制方面具有更大的灵活性。
