Smart Materials Laboratory, Department of Applied Physics, Northwestern Polytechnical University, Xi'an 710129, P. R. China.
Sci Rep. 2014 Apr 16;4:4713. doi: 10.1038/srep04713.
A visible negative-index metamaterial was fabricated by adopting a template-assisted and self-assembled electrochemical deposition method. Originating from the inherent characteristic of bottom-up fabrication, it has been demonstrated by the effective medium theory that the metamaterial resonance could realize a negative index at visible wavelengths if the degree of asymmetry is kept in a moderate range. This was experimentally substantiated by fabricating an asymmetric Ag-polyvinyl alcohol (PVA)-Ag multilayer nanostructure with two apertured silver films on the opposite sides of PVA film. The extraction of constitutive parameters shows negative index in the wavelength range from 535 to 565 nm, with a minimum value close to -0.5. Simultaneously, an optically active medium Rhodamine B was incorporated into the PVA layer, which readily changed the transmission peak through control experiments. Finally, the enhanced transmission was realized through a flat sample.
采用模板辅助自组装电化学沉积法制备了可见负折射率超材料。源于自下而上的制造固有特性，有效媒质理论表明，如果不对称度保持在适度范围内，超材料共振可在可见光波长下实现负折射率。通过在 PVA 薄膜两侧制备具有两个开口银膜的不对称 Ag-聚乙烯醇（PVA）-Ag 多层纳米结构，实验证实了这一点。本征参数的提取表明在 535nm 到 565nm 的波长范围内存在负折射率，最小值接近-0.5。同时，将具有光活性的 Rhodamine B 掺入 PVA 层中，通过控制实验很容易改变透过率峰。最后，通过平面样品实现了增强的传输。
