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We investigate band formation in one-dimensional periodic arrays of rectangular holes which have a nanoscale width but a length of 100 m. These holes are tailored to work as resonators in the terahertz frequency regime. We study the evolution of the electromagnetic response with the period of the array, showing that this dependence is not monotonic due to both the oscillating behavior of the coupling between holes and its long-range character. DOI: 10.1103/PhysRevLett.106.013902 PACS numbers: 41.20.Jb, 42.25.Fx, 42.79.Ag Band formation in covalent solids is mainly determined by the short-range electronic interaction between their constituent atoms [1]. Because of that, when forming a periodic array of N atoms with period d, the bandwidth enlarges when N increases and/or when d is reduced. Fundamental studies on how this picture is translated into the photonic case are scarce and were done in connection with the emergence of band gaps in dielectric photonic crystals [2][3][4]. In this Letter we carry out a fundamental analysis, both experimental and theoretical, of the photonic band formation in metallic structures. As an illustrating example, we consider as the constituent atom a very elongated rectangular hole perforated on a metal film. A single rectangular hole can support an electromagnetic (EM) resonance for light polarized along the short side of the rectangle [5,6], its spectral location appearing close to the cutoff wavelength of the hole waveguide [7]. Very recently, resonant field enhancements of up to 10 3 have been reported in the terahertz (THz) regime [8]. The transmission properties of periodic arrays of rectangular holes have also been analyzed [9][10][11][12], mainly in the context of the phenomenon of extraordinary optical transmission [13,14].Here we investigate EM band formation through the study of the evolution of the cutoff resonance of a rectangular hole as a 1D array of N resonators separated by a distance d is arranged [see sketch in Fig. 1(a)]. We will show how its EM response presents a nonmonotonic evolution with N and d, in contrast to its electronic counterpart. The experimental results are faithfully reproduced by numerical calculations. We also develop a minimal model that clearly relates the anomalous band formation to the long-range character of the interhole EM coupling.We have fabricated several 1D periodic arrays of rectangular holes, with a fixed length l ¼ 100 m and different widths around w ¼ 200 nm, perforated on 100 nm thick Au films deposited onto Si substrates, as shown schematically in Fig. 1(a). The period of the array is varied from 2 to 200 m. The arrays were fabricated by electron beam lithography [see Fig. 1(b)]. In our studies, we use the transmitted field through a large aluminum aperture of 1 mm  1 mm as a reference field [15]. Because the sample area is limited by the aperture, the number of holes depends on the period, ranging from N ¼ 5 holes for the case of d ¼ 200 m to N ¼ 500 for d ¼ 2 m. In order to obtain high signal-to-noise ratio, the 1D struct...

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. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

We report on the terahertz modulation based on the micro-and nano-sized apertures with metal-insulator phase transition of VO 2 thin film. Terahertz wave transmission through subwavelength apertures is controlled by temperature driven refractive index change of VO 2 substrate.

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