Wednesday, September 20, 2017

TERAHERTZ ELECTRONICS – WAY TO BRIDGE THE LARGELY-UNTAPPED REGION BETWEEN 100GHZ AND 10THZ


http://www.electronics-lab.com/terahertz-electronics-way-bridge-largely-untapped-region-100ghz-10thz/


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 Terahertz Gap
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.
Terahertz electronics technology offers practical applications in high-speed data transfer, THz imaging, and highly-integrated radar and communication systems. Surprisingly enough, It does not use semiconductors. Instead, it is based on metal-insulator tunneling structures to form diodes for detectors and ultra-high-speed transistors for oscillator based transmitters.
One drawback of the Terahertz Electronics is, it requires high-frequency radiation sources. Lack of a small, low-cost, moderate-power THz source is one of the main reasons that THz applications have not fully materialized yet. Scientists are trying to find a solution to this problem. They created a compact device that can lead to portable, battery-operated sources of THz radiation. This new solid-state T-ray source uses high-temperature superconducting crystals that contain stacks of Josephson junctions. So, even a small voltage, around two millivolts per junction, can induce frequencies in the THz range.





Mercury arc lamps generate light in terahertz




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.


Abstract-Electron beam induced terahertz Čerenkov radiation from multilayer graphene sandwiches


Konstantin Batrakov,   Sergey Maksimenko,

http://ieeexplore.ieee.org/document/7916335/

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.

Abstract-Photo-thermal-acoustic THz detection based on 3-dimensional graphene


Mostafa Shalaby, C. Vicario, Flavio Giorgianni, Stefano lupi, and Christoph P. Hauri

https://www.osapublishing.org/abstract.cfm?uri=cleo_qels-2017-JW2A.99&origin=search

We report on a novel, simple and efficient THz energy and intensity profile diagnostic tool which is based on the photo-thermo-acoustic (PTA) effect in a 3-dimensional graphene sponge.
© 2017 OSA

Abstract-Surface plasmons in a nanostructured black phosphorus flake



Xinyue Ni, Lin Wang, Jinxuan Zhu, Xiaoshuang Chen, and Wei Lu
Recent rediscovered layered material-black phosphorous with a puckered honeycomb atomic structure has experienced an upsurge in demand owing to its exotic physical properties such as layer-independent direct bandgap and linear dichroism. This Letter presents plasmonic properties of the nanostructured BP flake and its unprecedented capability of wide-band photon manipulation within the deep subwavelength scale. Owing to its anisotropic characteristic in band structure and moderate mobility, a strong layer number and polarization dependences of the plasmon resonance with frequencies ranging from infrared (IR) to terahertz have been found. Oblique plasmons have been observed in the square array of a black phosphorus (BP) flake, with the resonant frequency tuned in-situ, either electrically or optically, plus strong plasmon-induced absorption. Such advantages place BP as the best alternate candidate of plasmonic materials for ultra-scaled optoelectronic integration from terahertz to mid-IR.
© 2017 Optical Society of America

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

http://ieeexplore.ieee.org/document/7847400/

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.