Thursday, July 2, 2015

Abstract-Monte Carlo study of impact ionization in InSb induced by intense ultrashort terahertz pulses

The electron impact ionization dynamic has been investigated by Monte Carlo method in n-type InSb under the action of single-cycle pulses with 1 ps duration. The threshold electric field of impact ionization has been estimated to be about 8 kV/cm at 80 K. The number of generated carriers increases rapidly with increasing of electric field strength over threshold, and at 100 kV/cm, normalized electron concentration reaches 14. It is found that impact ionization process is dominant energy loss mechanism for hot carriers with energy larger than threshold energy of impact ionization. The results of calculations are compared with available experimental data. The agreement between theoretical calculations and experimental results was obtained.

Wednesday, July 1, 2015

Terahertz radiation system transmits data at 32 Gigabits per Second

French researchers have developed and successfully tested a terahertz system capable of transmitting data at a rate of 32 GB per second.
The researchers, working at the French Institute of Electronics, Microelectronics and Nanotechnology (IEMN) and using components produced by Orgeon, US-based optical test equipment manufacturer Tektronix, demonstrated a wireless system capable of transmitting data at 0.4 THz (400 GHz) using key advanced terahertz devices and advanced signal coding.
In the electromagnetic spectrum, terahertz waves occupy a band from 0.1 THz to 30 THz, the so-called “terahertz gap”, positioned between the optical and radio wavelength.
This band, despite being the least explored and developed part of the electromagnetic spectrum, is expected to play a key part in the quest to satisfy the increasing demand for higher speed wireless communication.
The promising nature of terahertz radiation, allied with its ability to penetrate a wide range of non-conducting materials, has been known to scientists for a considerable amount of time. The earliest images generated using the THz band were made in early 1960s.
The demand for faster wireless data traffic has followed as a result of drastic change in the way society creates and shares information. As predicted by a version of “Moore’s Law” appropriate for this technology, wireless data rates have doubled every 18-24 months over the last three decades. Conditional on this trend being followed, wireless Terabit-per-second (TBps) links may come on the market within the next decade.
One of the key motivations for developing transmission technologies using the THz spectrum is that wireless technologies below 0.1 THz cannot support Tbps links.
The fact that compact wireless technologies above 10 THz are not able to support Tbps links either, despite the large bandwith in the so-called Free Space Optical (FSO) communication systems, poses an additional constraint. As a result, new spectral bands are becoming required to support higher data rates. Terahertz Radiation Systems Market
In 2013 and 2014, the global market for terahertz radiation devices and systems was worth approximately $53 million and $54 million respectively.
Currently, the terahertz spectrum is not regulated and the market remains at a nascent stage of its development. However, the large bandwith provided by the THz band presents a highly attractive proposition.
We may soon see a broad range of networking applications, including 5G cellular networks, Terabit Wireless Local Area Networks (T-WLAN), Terabit Wireless Personal Area Networks(T-WPAN), as well as application of the THz band in ultra-broadband secure communication links in the military and defence fields.


Speaker: Richard Averitt, University of California San Diego (UCSD)
Abstract: The past decade has seen dramatic advances in creating active metamaterials (MM) with properties that can be dynamically modified and controlled with external stimuli, including optical excitation, electrical control, or mechanical actuation. A fair amount of this work has been at terahertz frequencies as this region of the electromagnetic spectrum is ripe for technological development while, from a fabrication point-of-view, providing rapid access to test new MM concepts and ideas. With the advent of pulsed terahertz sources capable of generating peak fields on the order of 1MV/cm, nonlinear THz “optics” is a new vista that, in concert with MM, offers exciting and scientific and technological opportunities. In this work, I will present some of our recent efforts exploring nonlinear THz MM. This includes the nonlinear response of InAs plasmonic disks and electron field emission arising from strong field localization and enhancement within the capacitive regions of metamaterial resonators.
Biosketch: Richard Averitt received his PhD degree in Applied Physics from Rice University for work on the synthesis and optical characterization of gold nanoshells. Following this, Richard was a Los Alamos National Laboratory Director’s Postdoctoral Fellow where his work focused on time resolved far-infrared spectroscopy of strongly correlated electron materials. In 2001, Richard became a member of the technical staff at Los Alamos, and in 2005 a member of the Center for Integrated Nanotechnologies co-located at Los Alamos and Sandia National Laboratories. In 2007, Richard joined Boston University as a faculty member in the Department of Physics and the Boston University Photonics Center. Since 2014, Richard has been with the Department of Physics at UC San Diego. Richard’s research is primarily directed towards characterizing, creating, and controlling the optical and electronic properties of complex materials. This includes correlated transition metal oxides and metamaterials.

Tuesday, June 30, 2015

Abstract-Terahertz near-field spectroscopy through sub-wavelength apertures

Oleg Mitrofanov and Irina Khromova
We demonstrate THz near-field spectroscopy of resonances in sub-wavelength size dielectric and conductive structures using the effect of enhanced transmission through a sub-wavelength aperture in the presence on a resonator.
© 2015 OSA
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Finnish start-up announces passive terahertz camera

Worried about the privacy and against harmful radiation inhibits the proliferation of so-called body scanners. A small company in Finland wants to defuse concerns both with a passive system.
The Finnish start-up Asqella , a spin-off from VTT Technical Research Centre wants to bring a rating based on the detection of terahertz waves camera on the market. Unlike previous systems they are even from no radiation, which is likely to mitigate health concerns. In addition, the camera does not produce accurate 3D images of people to be checked, so that the privacy is to be better protected. The international market launch is scheduled for the coming autumn, said CEO Arttu Luukanen towards Technology Review Online .
For about ten years, the exploration and use of terahertz radiation in the range between 100 microns and 1 millimeter, between microwaves and infrared intensified.So-called body or body scanners have been found after some initial difficulties widespread at airports around the world, also in Germany.
The heart of the passive system of Asqella loud Luukanen a so-called superconducting bolometer, ie a sensor for wide radiation measurements on thermal effects. However, the company initially not aimed at the market of airport security because of is to open a small party barely. Instead, the Finns think of checks on employees in storage centers or visitors at major events.
More at Technology Review Online:
(Sascha Mattke)