NTU Singapore scientists build ultra-high-speed Terahertz wireless chip

EurekAlert  August 5, 2020 Conventional approaches to terahertz waveguiding suffer from sensitivity to defects and sharp bends. Building on the topological phase of light, an international team of researchers (Singapore, Japan) experimentally demonstrated robust terahertz topological valley transport through several sharp bends on the all-silicon chip. The valley kink states are excellent information carriers owing to their robustness, single-mode propagation, and linear dispersion. They have demonstrated error-free communication through a highly twisted domain wall at an unprecedented data transfer rate (exceeding ten gigabits per second) that enables real-time transmission of uncompressed 4K high-definition video. The research opens a route towards […]

Underused part of the electromagnetic spectrum gets optics boost from metamaterial

Phys.org  July 14, 2020 Terahertz radiation potentially has applications in next-generation wireless communications (6G/7G), security systems, biomedicine, etc. because of the lack of appropriate materials and sophisticated optical components for flexible control of terahertz waves. Researchers in Japan have engineered a 2.28-µm ultra-thin terahertz metasurface collimator with a high directivity of 4.6 times consisting of 339 pairs of meta-atoms compared with a single terahertz continuous-wave source. The metasurface exhibits an extremely high refractive index of 15.0 and a low reflectance of 15.5% at 3.0 THz. It should facilitate ground-breaking applications such as arbitrary phase converters, solid immersion lenses, and cloaking…read more. […]

Research team presents novel transmitter for terahertz waves

Phys.org  March 16, 2020 If you irradiate pure germanium with a short laser pulse, it takes several microseconds before the electrical charge in the semiconductor disappears. Only then can the crystals absorb the next laser pulse. Gallium-arsenide crystals only deliver relatively narrowband terahertz pulses and thus a restricted frequency range. Researchers in Germany used gold implanted germanium to present ultrabroadband (extending up to 70 THz) THz emission that is compatible with mode-locked fibre lasers operating at wavelengths of 1.1 and 1.55 μm with pulse repetition rates of 10 and 20 MHz, respectively. This result opens the possibility for the development of compact THz […]

New graphene amplifier unlocks hidden frequencies in the electromagnetic spectrum

Nanowerk  February 3, 2020 An international team of researchers (South Korea, Russia, UK) propose a new type of optical transistor for broadband amplification of THz radiation. It is made of a graphene–superconductor hybrid, where electrons and Cooper pairs couple via Coulomb forces. The transistor operates via the propagation of surface plasmons in both layers, and the origin of amplification is the quantum capacitance of graphene. It leads to THz waves amplification, the negative power absorption, and as a result, the system yields positive gain, and the hybrid acts like an optical transistor, operating with the terahertz light. It can, in […]

Record-breaking terahertz laser beam

Phys.org  January 20, 2020 An international team of researchers (Greece, Austria, Qatar, Russia, Lithuania) has experimentally demonstrated that two-color filamentation of femtosecond mid-infrared laser pulses at 3.9 μm allows one to generate ultrashort sub-cycle THz pulses with sub-milijoule energy and THz conversion efficiency of 2.36%, resulting in THz field amplitudes above 100 MV cm−1. Numerical simulations predict that the observed THz yield can be significantly upscaled by further optimizing the experimental setup. They showed that the generated THz pulses are powerful enough to induce nonlinear cross-phase modulation in electro-optic crystals. The work paves the way toward free space extreme nonlinear THz optics using […]

Closing the terahertz gap: Tiny laser is an important step toward new sensors

EurekAlert  July 24, 2019 Current terahertz imaging technologies are expensive to produce and cumbersome to operate. A team of researchers in the US (Princeton University, MIT, University of Notre Dame, Sandia National Laboratory) has demonstrated hyperspectral imaging with chip-scale frequency combs based on terahertz quantum cascade lasers. The dual combs are free-running and emit coherent terahertz radiation that covers a bandwidth of 220 GHz at 3.4 THz with ∼10  μW per line. The combination of the fast acquisition rate of dual-comb spectroscopy with the monolithic design, scalability, and chip-scale size of the combs is highly appealing for future imaging applications in biomedicine […]

On-demand control of terahertz and infrared waves

Science Daily  July 9, 2019 According to a 2006 prediction it should be possible to use graphene in a magnetic field not only to absorb terahertz and infrared light on demand but also to control the direction of the circular polarization. An international team of researchers (Switzerland, UK) built a special experimental setup to concentrate the infrared and terahertz radiation on small samples of pure graphene in the magnetic field and the result of the experiment confirmed the theory from 2006. They found that if electrically charged carriers are introduced, either positive or negative, it is possible to choose which […]

New T-wave detector uses waves of the electronic sea in graphene

Nanowerk  December 21, 2018 It has proven challenging to implement plasmonic devices operating at terahertz frequencies. An international team of researchers (UK, Russia, Japan) has demonstrated plasmon-assisted resonant detection of terahertz radiation by antenna-coupled graphene transistors that act as both plasmonic Fabry-Perot cavities and rectifying elements. By varying the plasmon velocity using gate voltage, they could tune the detectors between multiple resonant modes. The devices offer a convenient tool for further plasmonic research and promise a viable route for various photonic applications… read more. Open Access TECHNICAL ARTICLE

First study of terahertz radiation in liquids

Phys.org  November 29, 2018 The most common sources of terahertz radiation are solid materials. An international team of researchers (USA – University of Rochester, Russia) provides fundamental insights into the THz wave generation process in water and an alternative perspective for studying laser-induced breakdown in liquids. They substantiate the radiation patterns of terahertz radiation in a liquid and its dependence on the angle at which the liquid collides with the pump radiation. They plan to solve the problem of THz absorption by optimizing the type of fluid, the shape of the jet and the pump power and several other parameters. […]

Graphene boosts GHz signals into terahertz territory

Nanowerk   November 19, 2018 An international team of researchers (Germany, the Netherlands, Spain) has generated terahertz harmonics up to the seventh order in single-layer graphene at room temperature and under ambient conditions, driven by terahertz fields of only tens of kilovolts per centimetre, and with field conversion efficiencies in excess of 10−3, 10−4 and 10−5 for the third, fifth and seventh terahertz harmonics, respectively. The results provide a direct pathway to highly efficient terahertz frequency synthesis using the present generation of graphene electronics, which operate at much lower fundamental frequencies of only a few hundreds of gigahertz…read more. TECHNICAL ARTICLE