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We present an electrically modulated nonlinear metamaterial at terahertz frequencies. The device consists of a planar array of split-ring resonators (SRRs) fabricated on n-type GaAs. Increasing the incident THz field strength induces carriers in the GaAs substrate, shorting the SRR capacitive gap and modulating the MM resonance. The application of a 15V bias to the MM reduces the net field modulation...
An ultrathin Terahertz (THz) quarter wave plate with high transmittance by flexible metamaterial is proposed in this paper. The device employs double layers of split ring resonator (SRR) with a polymer as the substrate. Due to the anisotropy of the SRR, it obtains a quarter wave plate with the transmittance of 0.72 and the ellipticity of 0.9994 at 0.854 THz from simulation. The device has a thickness...
We describe experimental characterization of switchable THz metasurfaces using variable-angle broadband THz ellipsometry. A theoretical framework is used to extract surface susceptibility tensors as a function of frequency and applied DC bias. This will allow us to make a priori predictions of the performance of these devices for applications as metasurface active components.
We report ultra-broadband, easily tuned, and highly efficient metamaterial terahertz wave retarders that are able to convert linear polarization into circular and elliptical polarization states. The broadband nature arises from the combination of the plasmonic effect and the property of polarization conversion. The dielectric response of the metamaterial microstructure and the angular phase dispersion...
Short-range wireless terahertz (THz) communication and ultrafast THz interconnects require switches and modulators. Here, we experimentally show voltage-bias superconducting (SC) niobium nitride (NbN) metamaterial to realize a switch. The obtained maximum transmission coefficient at 0.507 THz is up to 0.98 and it drops to 0.19 when the applied voltage is only increased to 0.9 V. A relative transmittance...
We report the first metamaterial tapered hyperlens for operation in the mid-infrared (3 μm) made of 470 tin wires embedded in soda-lime glass. The taper presents a magnification of 2x and is 62.5 μm in length. The structure on the smallest side has an average wire diameter and spacing of 300 and 600 nm, respectively. Preliminary modeling of the hyperlens indicates that the overall loss for the high...
A split-ring-resonator-based active metamaterial was investigated for manipulating the spatial intensity profile or wavefront of transmissive waves. In this work, varactor diodes were mounted at gaps in split-ring resonators to electrically control the waves. The fabricated active SRRs exhibit an ON/OFF ratio of 15 dB and a change in the transmission phase of 40o/layer by applying voltage to the varactor...
It is commonly believed that most of naturally occurring transparent materials have small positive refractive indices around 1 in the terahertz waveband. However, metamaterials have made a paradigm shift and achieve the design of man-made materials with both on-demand electromagnetic properties and unprecedented refractive indices. Here, inspired by the metamaterial concept, we report a transparent...
We will report our latest achievements with ultrathin NbN films for the development of conventional antenna coupled hot-electron-bolometer (AC-HEB) and of active metadevices, i.e. a frequency selective metamaterial with an integrated bolometer.
Utilizing THz wave to transmit data for communication and imaging places high demands in phase and amplitude modulation. In this paper we combined a metamaterial array with HEMT structure to form a multiband electronic grid-controlled THz modulator. By controlling the carrier concentration of 2DEG, resonant mode conversions between four different complex resonances have been realized. This mode conversion...
Rigid metamaterials were prepared by embedding TiO2 microspheres into polyethylene. These structures exhibit a series of Mie resonances where the lowest one is associated with a strong dispersion in the effective permeability. Using THz spectroscopy, we confirmed the magnetic nature of the observed resonance.
An opaque state that appears to be analogous to the electromagnetically induced transparency (EIT) phenomenon is generated using an asymmetric dimer of rectangular holes. By imaging in the near-field for the first time these metal hole arrays (MHAs) we find that the opaque state may be a result of constructive interference between the surface plasmon polaritons (SPPs) launched along the surface of...
We report on a novel waveguide concept which combines antiresonant and metamaterial guidance. The guidance is achieved in the hollow core and loss as low as 2.3 dB/km are theoretically achievable in the THz frequency range. Both purely antiresonant and antiresonant metamaterial fibers have been fabricated and characterized. The realized metamaterial fiber has been simulated to have 0.3 dB/m loss at...
In this contribution we study the fundamental interactions of a metamaterial system built of dipole elements in the THz regime. We investigate the coupling between the elements for different geometries, as well as symmetric and asymmetric structures and analyze the response of the system with changing refractive index of the surrounding medium. Finally, we use these structures to access intersubband...
We demonstrate a simple and cost-effective method for fabricating silver-nanoparticle metamaterial structures on a flexible substrate based on inkjet printing. Specifically, we used inkjet printing with an ordinary printer to obtain an array of split-ring resonators (SRRs) on a sheet of paper. We designed the SRR array to exhibit a resonance in the THz region, which we observed through THz time-domain...
We study the influence of THz surface plasmon polaritons (SPPs) on the Quality factor of complementary split ring resonator (cSRR) metasurfaces. By carefully tuning the SPP frequency, arising from the grating effect of the meta-atoms, into resonance with the LC-mode of a cSRR array, we observe effective linewidth broadening of the latter.
We present the first experimental realization of a terahertz (THz) waveguide that exhibits a negative effective index of refraction. To demonstrate this, we designed fabricated and characterized a linear array of three-dimensional structures that consist of split ring resonators and posts. THz radiation is launched and guided in the form of surface plasmon polaritons (SPPs) along the 3D metallic structures...
Checkerboard patterns (CPs) are a kind of metamaterials which have simple structure. Electromagnetic responses of CPs are unique and drastically changed by the configuration variation of self-complementary metal CPs. In this study, we investigated the influence of self-complementary metal CP configuration that consists of both capacitive CP and inductive CP, on transmittance of x- and j-polarized...
We present modified circular patch resonators and discuss their potential for coupling to semiconductor heterostructures. We theoretically investigated these structures in combination with asymmetric QWs for second-harmonic generation (SHG) and parametric conversion (PC). The Q-factor of modes of the bare (empty) circular plasmonic resonator is proved to be at least 40 and a mode overlap factor of...
Using the near-field time-domain terahertz spectroscopy, we detect the splitting of magnetic dipole resonance mode in strongly anisotropic mono-crystalline TiO2 micro-spheres. By fitting the Fano resonance model to the experimental data, we extract the intrinsic resonant properties of the micro-spheres and characterise their constituent dielectric material.
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