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THz metamaterials are employed to examine changes in the meta-resonances when two anisotropic organic materials, liquid crystal and carbon nanotubes, are placed on top of metamaterials. In both anisotropic double split-ring resonators and isotropic four-fold symmetric split-ring resonators, anisotropic interactions between the electric field and organic materials are enhanced in the vicinity of meta-resonances. In liquid crystal, meta-resonance frequency shift is observed with the magneto-optical coupling giving rise to the largest anisotropic shift. In carbon nanotube, meta-resonance absorptions, parallel and perpendicular to nanotube direction, experience different amount of broadening of Lorentzian oscillator of meta-resonance. Investigation reported here opens the application of metamaterials as a sensor for anisotropic materials. (C) 2012 Optical Society of America

A symmetric metamaterial superlattice is introduced accommodating a high Q-factor trapped mode. THz time-domain spectroscopy is employed to measure the transmission spectra, identifying the excitation of trapped and open-modes in the meta-resonances. A finite-difference-time- domain calculation showed that the trapped mode excitation is from the cancelation of current densities among the nearest-neighboring meta-particles. A cryogenic temperature THz measurement is carried out to examine the temperature dependence of resonance characteristics of meta-resonances. At low temperatures, the temperature-independent radiative damping is dominant for the open-mode, while the Q-factor of the trapped mode is determined by the temperature-dependent phonon scattering and temperature-independent defect scattering with the radiative damping significantly suppressed. When compared with the room temperature measurement, a 16% increase in Q-factor is observed for the trapped mode, while a 7% increase for the open-mode at the cryogenic temperature.

Terahertz metamaterial superlattice is fabricated with double-split ring resonators oriented alternately. By cooling down to cryogenic temperature 4K, changes in Q-factor of closed mode resonance originating from coherent coupling in metamaterial superlattice is investigated.

A superlattice structure of planar metamaterial is fabricated, where the orientation of double-split ring resonators is altered in a periodic way. A time-domain terahertz transmission spectrum shows an enhanced Q-factor resonance appears when a closed mode is selectively excited by angular tuning of polarization direction. The polarization-angle selective resonance in metamaterial superlattice has a potential application in the selective field enhancement for spectroscopy.