Wednesday, September 20, 2017
The terahertz (THz) region, which is based on 1THz frequency, separates electronics from photonics and has been difficult to access for ages. Semiconductor electronics cannot handle frequencies equal to or greater than 100GHz due to various transport-time related limitations. In other hand, photonics devices fail to work below 10THz as photon’s energy significantly drops to thermal energy. Terahertz Electronics (TE) is a new technology that extends the range of electronics into the THz-frequency region.
The main goal of Terahertz Electronics is to build a bridge between low-frequency “Electronics” and high-frequency “Photonics”. Since these devices use photon-electron particle interactions, as photon energy “hv” decreases below thermal energy “kT”, the device ceases to operate efficiently unless it is cooled down. At the low-frequency end, electronics cannot operate above 100GHz as transport time is dependent on drift and diffusion speeds of electrons/holes. As a result, a large region between 100GHz and 10THz remained inaccessible. Terahertz Electronics solves this problem efficiently by cleverly incorporating electronics with photonics.
TE devices are extremely fast and they are made entirely of thin-film materials—metals and insulator. Hence, it is possible to fabricate Terahertz Electronics devices on top of complementary metal oxide semiconductor (CMOS) circuitry—a technology for creating integrated-circuits circuitry or on an extensive variety of substrate materials. In TE devices, charge transport through the junction occurs via electron tunneling. Further research and development will make Terahertz Electronics a reality in not-so-distant future.
Konstantin Batrakov, Sergey Maksimenko,
Terahertz lasing by electron beam propagating over a graphene/dielectric sandwich structure is considered. A dispersion equation for the surface electromagnetic modes propagating along graphene sheets is derived and Čerenkov synchronism between surface wave and electron beam is predicted at achievable parameters of the system. The generation frequency tuning is proposed by varying the graphene doping, the number of graphene sheets, the distance between sheets, etc.
Mostafa Shalaby, C. Vicario, Flavio Giorgianni, Stefano lupi, and Christoph P. Hauri
Abstract-Broad- and Narrow-Line Terahertz Filtering in Frequency-Selective Surfaces Patterned on Thin Low-Loss Polymer Substrates
Antonio Ferraro, Dimitrios C. Zografopoulos, Roberto Caputo, Romeo Beccherell
A new class of frequency-selective surface filters (FSS) for terahertz (THz) applications is proposed and investigated both numerically and experimentally. A periodic FSS array of cross-shaped apertures is patterned on aluminum, deposited on thin foils of the low-loss cyclo-olefin polymer Zeonor. Apart from the fundamental filtering response of the FSS elements, we also observe very narrow-linewidth peaks with high transmittance, associated with guided-mode resonances in the dielectric substrate. The effect of the filter's geometrical parameters on its performance is systematically studied via finite-element method simulation and confirmed by time-domain spectroscopy characterization of the fabricated samples. Finally, thanks to the flexibility of the employed substrates, THz-FSS filters are also characterized in bent configuration, revealing a robust response in terms of the fundamental FSS passband filter and a high sensitivity of the GMR peaks. These features can be exploited in the design of novel THz filters or sensors.