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  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  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

U-M researchers develop small device that bends light to generate new radiation

University of Michigan  October 25, 2018 Synchrotron radiation is usually generated at large-scale facilities. A team of researchers in the US (University of Michigan, Purdue University) developed a way to produce synchrotron radiation by printing a pattern of microscopic gold antennae on lithium tantalate metasurface. They use a laser that produces ultrashort pulses of light which last for one trillionth of a second. The array of antennae causes the light pulse to accelerate along a curved trajectory inside the crystal producing synchrotron radiation that contains many terahertz frequencies. They hope to refine their device so that the light pulse revolves […]

Tuning terahertz beams with nanoparticles  September 6, 2018 A team of researchers in the US (UT San Antonio, Los Alamos National Laboratory) demonstrated that when an assembly of ferromagnetic core (cobalt ferrite) and a ferroelectric shell (barium titanate) is operated in external magnetic fields, it exhibits a controllable amplitude modulation when the magnetic field is applied antiparallel to the THz wave propagation direction; yet the same assembly displays an additional phase modulation when the magnetic field is applied along the propagation direction. Phase modulation is a result of stress-mediated piezoelectricity of the outer ferroelectric shell. The findings could enable tiny, high frequency transistors, create […]

Smaller and faster: The terahertz computer chip is now within reach

Science Daily  March 25, 2018 Using a Metal-Oxide-Nitride-Oxide-Silicon (MONOS) structure, researchers in Israel have designed a new integrated circuit that uses flash memory technology in microchips. If successful, this technology will enable standard 8-16 gigahertz computers to run 100 times faster and will bring all optic devices closer to the terahertz chip… read more. TECHNICAL ARTICLE