Scientists develop ultra-thin terahertz source

Phys.org  March 30, 2021 One of the biggest challenges in terahertz technology is that commonly accepted ‘intense terahertz source’ is faint and bulky. To overcome these limitations researchers in the UK developed terahertz sources from extremely thin materials (about 25 atomic layers). By illuminating an electronic-grade semiconductor with two different types of lasers light, each oscillating at different frequency they were able to elicit the emission of short bursts of Terahertz radiation. The emission region of their new development, a semiconductor source of terahertz, is 10 times thinner than previously achieved, with comparable or even better performances. They are able […]

Quantum tunneling in graphene advances the age of terahertz wireless communications

EurekAlert  February 3, 2021 As the radiation frequency is raised to the sub-terahertz (THz) domain, ac-to-dc conversion by conventional electronics becomes challenging and requires alternative rectification protocols. An international team of researchers (Russia, UK) address this challenge by tunnel field-effect transistors made of bilayer graphene (BLG). Taking advantage of BLG’s electrically tunable band structure, they created a lateral tunnel junction and couple it to an antenna exposed to THz radiation. The incoming radiation was then down-converted by the tunnel junction nonlinearity, resulting in high responsivity and low-noise detection. They demonstrated how switching from intraband Ohmic to interband tunneling regime can […]

Terahertz accelerates beyond 5G towards 6G

TechXplore  February 1, 2021 Researchers in Japan configured a two-channel terahertz transmitter (Tx) by modulating the output of a laser pair with wavelengths in the 1.55-micron band, which was set so that the frequency difference was in the 300-GHz band, with an 8K video signal source using an intensity modulator and converting it into terahertz waves using an ultrafast photodiode. After the wirelessly transmitted terahertz waves were detected by sensitive terahertz coherent receivers (Rxs) using resonant tunnel diodes (RTDs) they were split from the two channels into four channels and connected to an 8K monitor via HDMI cable. Using this […]

A trillion turns of light nets terahertz polarized bytes

Phys.org  October 19, 2020 Ultrafast nanophotonics is an emerging research field aimed at the development of nanodevices capable of light modulation with unprecedented speed. An international team of researchers (Italy, USA – Rice University) demonstrated that the inhomogeneous spacetime distribution of photogenerated hot carriers induces a transient symmetry breaking in a highly symmetric plasmonic metasurface. The process is fully reversible and results in a broadband transient dichroism with a recovery of the initial isotropic state in less than 1 ps, overcoming the speed bottleneck caused by slower (electron–phonon and phonon–phonon) relaxation processes. Their results pave the way to ultrafast dichroic devices […]

Breakthrough Could Lead to Amplifiers for 6G Signals

IEEE Spectrum  September 24, 2020 Researchers at UC Santa Barbara have been developing a device that could be critical to efficiently pushing 6G’s terahertz-frequency signals out of the antennas of future smartphones and other connected devices. They show that N-polar GaN deep recess HEMTs grown on sapphire match the power performance of a device on SiC up to 14 V with 5.1 W/mm of output power density. At 16 V the device on sapphire starts to suffer from thermal effects but still demonstrated 5.5 W/mm with an associated 20.6% power-added efficiency. This work also examines the impact of encapsulating the […]

Terahertz receiver for 6G wireless communications

Phys.org  September 8, 2020 Future 6G wireless networks will consist of a multitude of small radio cells that need to be connected by broadband communication links. An international team of researchers (Germany, USA – industry) has developed a novel concept for low-cost terahertz receivers that consist of a Schottky barrier diode that offers large bandwidth and that is used as an envelope detector to recover the amplitude of the terahertz signal. To overcome the problem of losing the time-dependent phase of the terahertz wave that is usually lost during rectification, they use digital signal processing techniques in combination with a […]

A breakthrough in developing multi-watt terahertz lasers

Phys.org  June 11, 2020 Plasmonic lasers suffer from low output power and divergent beams due to their subwavelength metallic cavities. A team of researchers in the US (Leigh University, Sandia National Laboratory) longitudinally coupled an array of metallic microcavities through traveling plasmon waves which led to radiation in a single spectral mode and a diffraction limited single-lobed beam in the surface normal direction. They implemented the scheme for terahertz plasmonic quantum-cascade lasers and measured peak output power in excess of 2W for a single-mode 3.3THz QCL radiating in a narrow single-lobed beam, when operated at 58K in a compact Stirling […]

Terahertz radiation can disrupt proteins in living cells

EurekAlert  June 2, 2020 Because terahertz radiation is stopped by liquids and is non-ionizing it is considered generally safe for use in the airports for scanning passengers. However, researchers in Japan have discovered that the energy from the light could enter into water as a “shockwave.” They investigated (G)-actin and (F)-actin, which have different structures and functions. Looking at the effect of terahertz radiation on the growth of chains in an aqueous solution of actin, they found that it led to a decrease in filaments, preventing the (G)-actin from forming chains and becoming (F)-actin. Ruling out the rise in temperature, […]

Energy-harvesting design aims to turn Wi-Fi signals into usable power

Phys.org  March 30,2020 Existing rectifiers are mostly based on semiconductor diodes, with limited applicability to small-voltage or high-frequency inputs. Researchers at MIT present an alternative approach to current rectification that uses the intrinsic electronic properties of quantum crystals without using semiconductor junctions. They identified a previously unknown mechanism for rectification from skew scattering due to the inherent chirality of itinerant electrons in time-reversal invariant but inversion-breaking materials. Their calculations reveal large, tunable rectification effects in graphene multilayers and transition metal dichalcogenides. Their work demonstrates the possibility of realizing high-frequency rectifiers by rational material design and quantum wave function engineering…read more. […]

Lasers and terahertz waves combined in camera that sees ‘unseen’ detail

Science Daily  February 18, 2020 The core challenge in THz cameras is not about collecting an image, but preserving the objects spectral fingerprint that can be easily corrupted by the technique. Researchers in the UK used a single-pixel camera to image sample objects with patterns of THz light. The prototype they built can detect how the object alters different patterns of THz light. By combining this information with the shape of each original pattern the camera reveals the image of an object as well as its chemical composition. The camera creates THz electromagnetic waves very close to the sample, similar […]