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Propagation properties of terahertz (THz) waves in a bounded atmospheric-pressure microplasma (AMP) are analyzed in this study. A modified Epstein profile model is used to simulate the electron density distribution caused by the plasma sheaths. By introducing the dielectric constant of a Drude-Lorentz model and using the method of dividing the plasma into a series of subslabs with uniform electron density, the coefficients of power reflection, transmission, and absorption are derived for a bounded microplasma structure. The effects of size of microplasma, electron density profile, and collision frequency on the propagation of THz waves are analyzed numerically. The results indicate that the propagation of THz waves in AMPs depend greatly on the above three parameters. It is demonstrated that the THz wave can play an important role in AMPs diagnostics; meanwhile, the AMP can be used as a novel potential tool to control THz wave propagation. [ABSTRACT FROM AUTHOR]

Terahertz (THz) waves have been attracting much attention for a variety of technologies in recent years. However, only limited several experimental investigations on the terahertz characterization of plasmas have been reported. In this paper, a finite-difference time-domain method is applied to model the terahertz wave propagation in a high-temperature unmagnetized plasma. The rational polynomial function is established based on a hot plasma dispersion relation, and then, the relationship between D and E is deduced in the time domain. In the frequency domain, the reflection and transmission coefficients of terahertz waves through the hot unmagnetized plasma slab are computed, and their dependences on plasma frequency, plasma thickness, and collision frequency are studied. The results show theoretically that, when the terahertz wave passes through the plasma layer, its amplitude is obviously modulated by the electron density profile, the collision frequency, and the electron temperature. Finally, the potential application of terahertz waves in plasma diagnostics has been discussed. [ABSTRACT FROM PUBLISHER]

We characterize the behavior of split ring resonators made up of high transition temperature yttrium barium copper oxide superconductor using terahertz time-domain spectroscopy measurements and numerical simulations. The superconductor metamaterial is found to show a remarkable change in the transmission spectra at the fundamental inductive-capacitive resonance as the temperature dips below the critical transition temperature. This resonance switching effect is normally absent in traditional metamaterials made up of regular metals. The temperature-dependent resonance behavior of the superconducting metamaterial would lead to development of low loss terahertz switches at cryogenic temperatures. [ABSTRACT FROM AUTHOR]