Article

Tuning the resonance in high-temperature superconducting terahertz metamaterials.

MPA-CINT, MS K771, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
Physical Review Letters (Impact Factor: 7.73). 12/2010; 105(24):247402. DOI: 10.1103/PhysRevLett.105.247402
Source: arXiv

ABSTRACT In this Letter, we present resonance properties in terahertz metamaterials consisting of a split-ring resonator array made from high-temperature superconducting films. By varying the temperature, we observe efficient metamaterial resonance switching and frequency tuning. The results are well reproduced by numerical simulations of metamaterial resonance using the experimentally measured complex conductivity of the superconducting film. We develop a theoretical model that explains the tuning features, which takes into account the resistive resonance damping and additional split-ring inductance contributed from both the real and imaginary parts of the temperature-dependent complex conductivity. The theoretical model further predicts more efficient resonance tuning in metamaterials consisting of a thinner superconducting split-ring resonator array, which are also verified in subsequent experiments.

0 Bookmarks
 · 
107 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We demonstrate an all-optical terahertz modulator based on single-layer graphene on germanium (GOG), which can be driven by a 1.55 μm CW laser with a low-level photodoping power. Both the static and dynamic THz transmission modulation experiments were carried out. A spectrally wide-band modulation of the THz transmission is obtained in a frequency range from 0.25 to 1 THz, and a modulation depth of 94% can be achieved if proper pump power is applied. The modulation speed of the modulator was measured to be ~200 KHz using a 340 GHz carrier. A theoretical model is proposed for the modulator and the calculation results indicate that the enhanced THz modulation is mainly due to the third order nonlinear effect in the optical conductivity of the graphene monolayer.
    Scientific Reports 12/2014; 4:7409. · 5.08 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present a complementary THz metasurface realised with Niobium thin film which displays a quality factor Q=54 and a fully switchable behaviour as a function of the temperature. The switching behaviour and the high quality factor are due to a careful design of the metasurface aimed at maximising the ohmic losses when the Nb is above the critical temperature and minimising the radiative coupling. The superconductor allows the operation of the cavity with an high Q and inductive elements with an high aspect ratio. Comparison with three dimensional finite element simulations highlights the crucial role of the inductive elements and of the kinetic inductance of the Cooper pairs in achieving the high quality factor and the high field enhancement. Metamaterials 1–3 proved in the last 15 years to be an extremely flexible and useful concept 4 that has been im-plemented in many different contexts, from fundamental research 5 to applications 6 . The possibility to engineer the electromagnetic response of surfaces and materials 7 with 2D 8 and 3D structures 9–11 with constitutive ele-ments much smaller than the wavelength has opened new and exciting possibilities, from integrated optics 12 to solid state physics 13 and strong light-matter coupling 14 , just to name a few. Recently, we reported on experiments on ultrastrong light-matter coupling at THz frequencies with supercon-ducting Niobium (Nb) metasurfaces 15 . In order to ad-dress theoretical predictions on peculiar cavity QED ef-fects which arise in such ultrastrong coupling regime 16–19 , it is necessary to be able to perform non-adiabatic exper-iments at THz frequencies. Superconducting metamate-rials have been investigated in the THz 20–24 and super-conductors (SC) indeed display transition times of the order of the ps 25,26 when illuminated with high intensity, ultrafast optical pulses. The objective of our study is the realisation of a metasurface operating in the THz with high quality factor and displaying a pronounced switch-ing behaviour. We would like to achieve a metasurface that displays a two-state behaviour: a narrow band, high transmission in the range 200-400 GHz (well below the Nb gap frequency of 730 GHz) that can be commuted to a broadband, low transmission. At the same time, since we are interested in cavity QED at THz frequencies 14 , we aim at realising a meta-atom which provides a very small mode volume, in order to enhance the vacuum field fluctuations that scale as E vac ∼
    Applied Physics Letters 11/2014; · 3.52 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, a point has been proposed that coupling current exist in terahertz devices, especially some typical structures, such as split ring resonators. Gaps are no longer treated as capacitances are not exact. By varying the width of gap, a kind of relationship between coupling ratio and gap's width has been made. And it has been testified to be approximately suitable in some other structures. Equivalent electrical length has been brought in to explain how the currents with the same orient cause resonance, of which fabricate a frequency band, via S parameter. Our work may open another method to explain electromagnetic wave resonating in metal structure.
    2013 IEEE International Conference on Applied Superconductivity and Electromagnetic Devices (ASEMD); 10/2013

Full-text (3 Sources)

Download
46 Downloads
Available from
May 16, 2014