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Dielectric films with a thickness much less than a wavelength pose a challenge in transmission-mode terahertz time-domain spectroscopy (THz-TDS). A small signal change induced by such films is likely to be obscured by system uncertainties. In this abstract, several possible thin-film measurement procedures are carefully considered. It is found that an alternating sample and reference measurement approach...
Resonant excitation of planar terahertz metamaterials using attenuated total reflection is demonstrated. Experimental results reveal an anomalous increase in the resonance strength while the sample is illuminated near the edge of the metamaterial array with a finite-size terahertz beam. A re-radiation signal at the fundamental metamaterial resonance is observed on the transmission side of the total...
We demonstrate broadening of fundamental resonance by successive insertion of rings inside of a split ring resonator (SRR) in a nested fashion. With the maximum inner rings, the resonance linewidth broadens by factor of four.
We demonstrate reconfigurable metamaterial by actively switching constituent resonators from split-ring to closed-ring configuration. Both fundamental and third order resonances damps out while the second order resonance emerges at high pump power.
We experimentally and numerically study the nature of coupling between laterally paired terahertz metamaterial split-ring resonators. Coupling is shown to modify the inductive-capacitive (LC) resonances resulting in either red or blue-shifting. These experiments illustrate additional degrees of freedom in tuning the electromagnetic response of metamaterials.
We measure for the first time at terahertz frequencies, independent of background signal, the radiation due to the fundamental resonance of a split ring oscillator array. A reference free method of probing metamaterial resonance via attenuated total reflection is demonstrated.
We present a series of novel THz metamaterials with designed active functionality, enabling dynamic tuning of the amplitude, frequency and polarization state of a THz wave.
We report tunable resonances in terahertz metamaterials made from high-temperature superconducting films. Taking in account the temperature-dependent complex conductivity, we develop a theoretical model for correct interpretation of the observed resonance switching and frequency tuning.
Bilayer split ring resonators as a function of separation (∼λ /500) and orientation are measured. Terahertz measurements match simulations showing frequency shifting of the resonances with implications for electrically small antenna design.
We demonstrate active tuning of coupled inductive-capacitive resonance in a multi-layer metamaterial. Our experiment reveals that one resonance mode of a coupled pair can be selectively switched off by driving the metamaterial with infrared light.
We present a perfect terahertz absorber that operates over numerous incidence angles. The two-fold symmetry of rectangular fishnet structures allows either complete absorption or mirror-like reflection depending on the orientation of the electric field.
We present a hybrid metamaterial semiconductor device capable of 20% tunability of the center resonance frequency via photoexcitation of the semiconductor regions, thereby addressing the metamaterials drawback of narrow bandwidth operation.
We demonstrated electronically switchable extraordinary terahertz transmission through sub-wavelength metallic hole arrays fabricated on doped semiconductor substrates. A reverse voltage bias results in a controllable depletion thus tuning the substrate loss and switching the transmission.
Planar electric metamaterials fabricated on thin, flexible substrates are studied using terahertz-time domain spectroscopy. Transmission measurements are performed to analyze dielectric properties on single and multiple stacked samples and reveal strong resonances at 1.2 THz.
A lumped-element circuit model is shown to accurately describe the behavior of terahertz metafilms, or planar metamaterials. The model provides insight into the proper application of effective medium approximations in determining metafilm constitutive parameters.
We investigate the limitations of using THz metamaterials as thin-film chem-bio sensors, by depositing dielectric overlayers onto split-ring resonator arrays. We also study resonance shifts by conjugating biomolecules using avidin/silane linkers attached to the resonators.
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