Doubly Tunable Metamaterials

Thin layers of semiconductors, superconductors, correlated electron systems, and polymers are the core elements of modern science and technology. Metamaterials research also heavily utilizes thin films, nonlinear index increases of which caused by photo-excitation, voltage, or temperature have been used to actively control technologically important long wavelength electromagnetic waves. These control attempts are however met with only partial success, because the l/1,000 ~ l/100,000 films are optically too thin even considering the large dielectric constants, and also because the control has limited spectral range around resonance. Here, we show that broadband, long wavelength nano antennas on VO2 (vanadium dioxide) films, initially transparent to incoming electromagnetic waves, achieve a 100,000 to 1 extinction by phase transition of the underlying thin film, thereby increasing the dielectric constant to over 500,000. Our scheme, utilizing strongly evanescent wavevector components below the nanoscale features, offering orders of magnitudes tenability of nonlinearities and dielectric constants, bridges the gap between thin film technology, nanotechnology, and active metamaterials researches.