A repository & source of cutting edge news about emerging terahertz technology, it's commercialization & innovations in THz devices, quality & process control, medical diagnostics, security, astronomy, communications, applications in graphene, metamaterials, CMOS, compressive sensing, 3d printing, and the Internet of Nanothings. NOTHING POSTED IS INVESTMENT ADVICE! REPOSTED COPYRIGHT IS FOR EDUCATIONAL USE.
Advanced nanophotonics penetrates into other areas of science and technology, ranging from applied physics to biology and resulting in many fascinating cross-disciplinary applications. It has been recently demonstrated that suitably engineered light-matter interactions at the nanoscale can overcome the limitations of today's terahertz (THz) photoconductive antennas, making them one step closer to many practical implications. Here we push forward this concept by comprehensive numerical optimization and experimental investigation of a log-periodic THz photoconductive antenna coupled to a silver nanoantenna array. We shed light on the operation principles of the resulting hybrid THz antenna, providing an approach to boost its performance. By tailoring the size of silver nanoantennas and the distance between them, we obtain an enhancement of optical-to-THz conversion efficiency 2-fold larger compared with previously reported results, and the strongest enhancement is around 1 THz, a frequency range barely achievable by other compact THz sources. Moreover, we propose a cost-effective fabrication procedure to realize such hybrid THz antennas with optimized plasmonic nanostructures via thermal dewetting process, which does not require any post processing and makes the proposed solution very attractive for applications.
We propose here a new platform to realize a plethora of graphene-based plasmonic nanodevices for frequency-agile terahertz (THz) frontend circuits. We demonstrate that a class of hybrid electronic-plasmonic nanodevices combining active graphene field-effect transistors (GFET) and graphene plasmonic waveguides (GPWG) supporting tightly-confined propagation of THz signals, with tailored phase velocity and characteristic impedance controlled by the gate and drain voltages of GFET. We propose a variety of reconfigurable graphene-based nanodevices based on this general architecture, including reconfigurable and electronically-programmable phase-shifters, filters, impedance transformers, modulators, and terminators. We envision the integration of these active THz circuit elements into a fully reconfigurable THz system as a fundamental step towards new design architectures and protocols for THz communication, sensing, actuation, and biomedical applications.
Scientists from the Cockrell School of Engineering at the University of Texas at Austin realized a 400-nanometer-thick nonlinear mirror that reflects radiation at twice the input light frequency. Credit: Cockrell School of Engineering, The University of Texas at Austin
Researchers at the Cockrell School of Engineering at The University of Texas at Austin have created a new nonlinear metasurface, or meta mirror, that could one day enable the miniaturization of laser systems.
The invention, called a "nonlinear mirror" by the researchers, could help advance nonlinear laser systems that are used for chemical sensing, explosives detection, biomedical research and potentially many other applications. The researchers' study will be published in the July 3 issue of Nature.
The metamaterials were created with nonlinear optical response a million times as strong as traditional nonlinear materials and demonstrated frequency conversion in films 100 times as thin as human hair using light intensity comparable with that of a laser pointer.
Nonlinear optical effects are widely used by engineers and scientists to generate new light frequencies, perform laser diagnostics and advance quantum computing. Due to the small extent of optical nonlinearity in naturally occurring materials, high light intensities and long propagation distances in nonlinear crystals are typically required to produce detectable nonlinear optical effects.
The research team led by UT Austin's Department of Electrical and Computer Engineering professors Mikhail Belkin and Andrea Alu, in collaboration with colleagues from the Technical University of Munich, has created thin-film nonlinear metamaterials with optical response many orders of magnitude larger than that of traditional nonlinear materials. The scientists demonstrated this functionality by realizing a 400-nanometer-thick nonlinear mirror that reflects radiation at twice the input light frequency. For the given input intensity and structure thickness, the new nonlinear metamaterial produces approximately 1 million times larger frequency-doubled output, compared with similar structures based on conventional materials.
"This work opens a new paradigm in nonlinear optics by exploiting the unique combination of exotic wave interaction in metamaterials and of quantum engineering in semiconductors," said Professor Andrea Alu.
The metamaterial at the basis of this unusual optical response consists of a sequence of thin layers made of indium, gallium and arsenic on the one hand and aluminum, indium and arsenic on the other. The researchers stacked approximately 100 of these layers, each between 1 nanometer and 12 nanometers thick, and sandwiched them between a layer of gold at the bottom and a pattern of asymmetric gold nanocrosses on top. The thin semiconductor layers confine electrons into desired quantum states, and gold nanocrosses resonate at input and output frequencies to enable the the nonlinear optical response of the mirror.
