Terahertz mode selector based on multimode resonances in corrugated waveguides
01 Aug 2021-Journal of The Optical Society of America B-optical Physics (Optical Society of America)-Vol. 38, Iss: 8, pp 2323-2328
TL;DR: In this paper, a magnetically switchable terahertz (THz) mode selector based on four transverse mode resonances in corrugated waveguides is proposed.
Abstract: We propose a magnetically switchable terahertz (THz) mode selector based on four transverse mode resonances in corrugated waveguides. The theoretical and numerical results show that two passbands can be obtained in the transmission spectra around the resonance points. The passband of 0.9611–1.0006 THz outputs a single second-order transverse mode with the highest ratio of 99.03% while the passband of 0.8712–0.9111 THz contains the multiple transverse mode output with the first two modes. A tunable THz mode selector with frequency band of 0.5572–0.5926 THz is realized by filling the waveguide core with a liquid crystal (E7). The widest working frequency range of the mode selector reaches 28.4 GHz when the molecular steering angle θ lies between 71.22° and 90°.
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01 Jan 2009
TL;DR: In this article, the optical and electrical properties of several composites, formed by filling the high density polyethylene (HDPE) with similar amount of carbon black (CB), multi-walled carbon nanotubes (MWNT) and fullerene (C(60)), respectively, were characterized using a THz-TDS setup.
Abstract: The optical and electrical properties of several composites, formed by filling the high density polyethylene (HDPE) with similar amount of carbon black (CB), multi-walled carbon nanotubes (MWNT) and fullerene (C(60)), respectively, were characterized using a THz-TDS setup. It was found that the optical parameters and the details of their variation with frequency differ significantly for different kinds of carbon materials. The results are analyzed by using Cole-Cole formula of dipole relaxation under the assumption that carbon particles dispersed in the matrix behave like dipoles and contribute mainly to the dielectric loss in the THz frequency range. Fitting results indicate that MWNT and CB filled composites have a broader distribution of the relaxation time compared with C(60) which possesses a nearly single relaxation time. Compared with CB and C(60), MWNT filled composite possesses the larger relaxation strength due to its higher electron density and larger conductive clusters. The real part of conductivity for three kinds of composites all follows power law behavior with respect to frequency but the exponents are quite different. These phenomena may be related to the special properties of the fillers as well as their particulate structures, such as aspect ratio, particle size, and aggregate structure, etc.
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TL;DR: The data for the noble metals and Al, Pb, and W can be reasonably fit using the Drude model and it is shown that -epsilon1(omegas) = epsilon2(omega) approximately omega(2)(p)/(2omega( 2)(tau) at the damping frequency omega = omega(tau), where the plasma frequency is omega(p).
Abstract: Infrared optical constants collected from the literature are tabulated. The data for the noble metals and Al, Pb, and W can be reasonably fit using the Drude model. It is shown that -epsilon1(omega) = epsilon2(omega) approximately omega(2)(p)/(2omega(2)(tau)) at the damping frequency omega = omega(tau). Also -epsilon1(omega(tau)) approximately - (1/2) epsilon1(0), where the plasma frequency is omega(p).
2,014 citations
TL;DR: The results show that fundamental light interactions of surfaces can be dynamically controlled by all-electronic means and provide a path forward for realization of novel applications.
Abstract: We present an experimental demonstration of electronically tunable metamaterial absorbers in the terahertz regime. By incorporation of active liquid crystal into strategic locations within the metamaterial unit cell, we are able to modify the absorption by 30% at 2.62 THz, as well as tune the resonant absorption over 4% in bandwidth. Numerical full-wave simulations match well to experiments and clarify the underlying mechanism, i.e., a simultaneous tuning of both the electric and magnetic response that allows for the preservation of the resonant absorption. These results show that fundamental light interactions of surfaces can be dynamically controlled by all-electronic means and provide a path forward for realization of novel applications.
480 citations
TL;DR: In this Perspective article, a few important examples are discussed: the development of methods to access nonlinear optical effects in the terahertz range; methods to probe nanoscale phenomena; and, the growing likelihood that teraHertz technologies will be a critical player in future wireless networks.
Abstract: The field of terahertz science and technology has been an active and thriving research area for several decades. However, the field has recently experienced an inflection point, as several exciting breakthroughs have enabled new opportunities for both fundamental and applied research. These events are reshaping the field, and will impact research directions for years to come. In this Perspective article, I discuss a few important examples: the development of methods to access nonlinear optical effects in the terahertz range; methods to probe nanoscale phenomena; and, the growing likelihood that terahertz technologies will be a critical player in future wireless networks. Here, a few examples of research in each of these areas are discussed, followed by some speculation about where these exciting breakthroughs may lead in the near future.
252 citations
TL;DR: The terahertz portion of the electromagnetic spectrum is perhaps the last largely-unexplored wavelength frontier for astronomical observations as discussed by the authors, and it is also one of the most diagnostic, harboring spectral signatures of ions, atoms, and molecules that are central to our understanding of the composition and origin of the Solar System, the evolution of matter in our Galaxy, and the star formation history of galaxies over cosmic timescales.
Abstract: The terahertz portion of the electromagnetic spectrum is perhaps the last largely-unexplored wavelength frontier for astronomical observations. It is also one of the most diagnostic, harboring spectral signatures of ions, atoms, and molecules that are central to our understanding of the composition and origin of the Solar System, the evolution of matter in our Galaxy, and the star formation history of galaxies over cosmic timescales. In this brief overview, specific astronomical applications of terahertz spectroscopy will be highlighted with examples of current heterodyne capabilities, and projection of future astronomical demands upon terahertz instrumentation.
172 citations
TL;DR: Tunable phase shift up to 360 degrees at 1 THz is achieved with a liquid crystal (LC) device using a nematic LC, E7, which exhibits a birefringence of ~ 0.17.
Abstract: Tunable phase shift up to 360° at 1 THz is achieved with a liquid crystal (LC) device. The key to this design is (1) the use of a nematic LC, E7, which exhibits a birefringence of ~0.17 (0.2–1.2 THz); (2) a LC cell (3-mm in thickness) with sandwiched structure to increase the interaction length while minimizing interface Fresnel losses; and (3) the use of magnetic field to align the thick LC cell and achieve continuous tuning of phase from 0 to 360°. This device can be operated over a broad range near room temperature.
136 citations