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 […]
Tag Archives: Terahertz technology
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 […]
Using long-wavelength terahertz radiation to produce video with a high frame rate
Phys.org February 10, 2020 Long-wavelength terahertz radiation which is considered to be much safer than X-ray radiation has not been used in security and medical devices because its energy is so low and it has been difficult to create high-resolution images using them. Instead of building a more sensitive sensor researchers in the UK made the waves more readable to conventional technology. They converted the terahertz radiation into green light by directing it into a cloud of excited cesium atoms. Once the cloud was formed, the researchers fired a secondary terahertz laser through a moving object, which allowed a “shadow […]
Using sound and light to generate ultra-fast data transfer
Science Daily February 11, 2020 To be able to send data at increased speeds, the lasers need to be modulated very rapidly: switching on and off or pulsing around 100 billion times every second. Instead of using external electronics, researchers in the UK used acoustic waves to vibrate the quantum wells inside the quantum cascade laser. The acoustic waves were generated by the impact of a pulse from another laser onto an aluminium film that caused the film to expand and contract, sending a mechanical wave through the quantum cascade laser. They were able to control the light output by […]
Laser combo opens up futuristic terahertz technology
Physics World November 25, 2019 The terahertz region of the electromagnetic spectrum has been the least utilized owing to inadequacies of available sources. A team of researchers in the US (Harvard University, MIT, Duke University) has created a compact, widely frequency-tunable, extremely bright source of terahertz radiation: a gas-phase molecular laser based on rotational population inversions optically pumped by a quantum cascade laser. By identifying the essential parameters that determine the suitability of a molecule for a terahertz laser, almost any rotational transition of almost any molecular gas can be made to lase. Nitrous oxide is used to illustrate the […]