Active terahertz metamaterials: Nano-slot antennas on VO₂ thin films

We demonstrate a broadband metamaterial based on nano-slot antenna on a VO₂ thin film, which transforms itself from transparent to completely extinct over a broad spectrum when the underlying VO₂ thin film makes Mott-insulator-to-metal phase transition. Our structure, long wavelength nano resonators inspired by log-periodic antenna, has 2 terahertz (THz) wide spectral range with 10,000: 1 extinction ratio through thermal and photo excitation. Two of the most important demands for present metamaterials research, broadband operation and full transmission/extinction control, are met in our metamaterial. Our structure enables nano-scale thin film technology to fully enter into long wavelength applications, and we foresee a wide range of applications in areas where perfect modulation, giant nonlinearity, switching, and filtering in broad THz bands are desired.