Science Daily April 22, 2022 Researchers at UC Irvine positioned two bound atoms of hydrogen in between the silver tip of the scanning tunneling microscope (STM) and a sample composed of a flat copper surface arrayed with small islands of copper nitride. With pulses of the laser lasting trillionths of a second, they were able to excite the hydrogen molecule and detect changes in its quantum states at cryogenic temperatures and in the ultrahigh vacuum environment of the instrument, rendering atomic-scale, time-lapsed images of the sample. The STM was equipped to detect minute electrical current flowing in this space and […]
Tag Archives: Terahertz technology
An innovative technology for 6G communication networks
Science Daily February 15, 2022 Terahertz waveguides are required to provide versatile signal-processing functionalities. Despite fundamental components they typically rely on complex hybridization, in turn making it extremely challenging to go beyond the most elementary functions. An international team of researchers (Canada, Italy, Germany) has proposed a universal approach, in which multiscale-structured Bragg gratings can be directly etched on metal-wires. They designed a four-wire waveguide geometry, amenable to support the low-loss and low-dispersion propagation of polarization-division multiplexed terahertz signals. By engraving on the wires judiciously designed Bragg gratings based on multiscale structures, they demonstrated that it is possible to independently […]
A leap forward for terahertz lasers
Science Daily January 26, 2022 Despite decades of research, no frequency tunable sources span the terahertz gap between 0.3 and 3 THz. By introducing methyl fluoride (CH3F) as a new gain medium for a quantum cascade laser-pumped molecular laser (QPML), a team of researchers in the US (Harvard University, industry, DEVCOM ARL, Duke University) has demonstrated continuous-wave lasing from more than 120 discrete transitions, spanning the range from 0.25 to 1.3 THz. Due to its large permanent dipole moment and large rotational constants, methyl fluoride (CH3F) as a QPML gain medium combines a lower threshold, a larger power efficiency, and […]
Ultrafast imaging of terahertz electric waveforms using quantum dots
Phys.org January 4, 2022 Only few imaging schemes can resolve sub-wavelength fields in the THz range, such as scanning-probe techniques, electro-optic sampling, and ultrafast electron microscopy. The intrinsic constraints on sample geometry, acquisition speed and field strength limit their applicability. An international team of researchers (Germany, Australia) harnessed the quantum-confined Stark-effect to encode ultrafast electric near-fields into colloidal quantum dot luminescence. Their approach, termed Quantum-probe Field Microscopy (QFIM), combines far-field imaging of visible photons with phase-resolved sampling of electric waveforms. By capturing ultrafast movies, they spatio-temporally resolved a Terahertz resonance inside a bowtie antenna and unveiled the propagation of a […]
New chip hides wireless messages in plain sight
Science Daily November 23, 2021 Traditional encryption methods are challenging to scale for high-bandwidth, ultralow-latency applications. An alternative approach is to use physical-layer techniques that rely on the physics of signal propagation to incorporate security features without the need for an explicit key exchange. Ensuring security using directional, narrow-beam-like features of mm-wave/THz signals has proven to be vulnerable to passive eavesdroppers. An international team of researchers (USA – Princeton University, China) has developed a space-time modulation approach that ensures security by enforcing loss of information through selective spectral aliasing towards the direction of eavesdroppers, even though the channel can be […]
New phonon-based and magneto-tunable monochromatic terahertz source
Phys.org November 10, 2021 Researchers in China developed a highly efficient magneto-tunable and phonon-based monochromatic THz generator with a frequency of ~0.9 THz using a 2D ferromagnetic Cr2Ge2Te6 crystal. They combined theoretical and experimental approaches and innovatively exploited the excellent properties of its van der Waals interlayered breathing phonon mode (boson) with THz-TDS (time domain spectroscopy) magneto-optic system. They found the breathing mode could effectively couple with incident co-frequency THz pulse and form a phonon-polariton. This quasi-bosonic particle could then generate far-field electro-magnetic radiation with monochromatic frequency comparable to the phonon mode. They regulated the radiation via the spin-phonon interaction […]
Researchers develop broadband spintronic-metasurface terahertz emitters with tunable chirality
Phys.org October 26, 2021 Researchers in China made laser-driven terahertz emitters, consisting of metasurface-patterned magnetic multilayer heterostructures that can overcome the shortcomings of the conventional approaches. They have demonstrated the efficient generation and manipulation of broadband chiral terahertz waves. The emitter’s ellipticity can reach >0.75 over a broad terahertz bandwidth (1 to 5 THz), it is an efficient source for few-cycle circularly polarized terahertz pulses with stable carrier waveforms, and has flexible control of ellipticity and helicity. They have shown that the terahertz polarization state is dictated by the interplay between laser-induced spintronic-origin currents and the screening charges/currents in the […]
Quantum material to boost terahertz frequencies
Science Daily October 20, 2021 An international team of researchers (Germany, Spain, Russia) investigated the ultrafast carrier dynamics in topological insulators (TIs) of the bismuth and antimony chalcogenide family, where they isolated the response of Dirac fermions at the surface from the response of bulk carriers by combining photoexcitation with below-bandgap terahertz (THz) photons and TI samples with varying Fermi level, including one sample with the Fermi level located within the bandgap. They identified distinctly faster relaxation of charge carriers in the topologically protected Dirac surface states, compared to bulk carriers and they observed THz harmonic generation without any saturation […]
The demonstration of ultrafast switching to an insulating-like metastable state
Phys.org July 13, 2021 Superconductors host collective modes that can be manipulated with light. An international team of researchers (Japan, France) has shown that a strong terahertz light field can induce oscillations of the superconducting order parameter in NbN with twice the frequency of the terahertz field. The result can be captured as a collective precession of Anderson’s pseudospins in ac driving fields. A resonance between the field and the Higgs amplitude mode of the superconductor then results in large terahertz third-harmonic generation. Their method paves a way toward nonlinear quantum optics in superconductors with driving the pseudospins collectively and […]
Using micro-sized cut metal wires, team forges path to new uses for terahertz waves
Phys.org May 14, 2021 Terahertz flat optics is a design concept for replacing conventional three-dimensional bulky optical components with two-dimensional ultra-thin optical components. However, high refractive index materials suitable for flat optics are frequently subject to high Fresnel reflections due to the cumbersome control of the relative permeability it requires. Researchers in Japan fabricated metasurface consisting of 80,036 pairs of cut metal wires on both the front and back of a 5 μm-thick polyimide film with a super-fine ink-jet printer using silver paste ink. They have experimentally shown that the metasurface is reflectionless, has a high refractive index, extremely low […]