Phys.org July 10, 2024 Manipulating the polarization of light at the nanoscale is key to the development of next-generation optoelectronic devices. This is typically done via waveplates using optically anisotropic crystals, with thicknesses on the order of the wavelength. A team of researchers in the US (Stanford, SLAC Nation Acceleration Laboratory, Harvard University, Columbia University, Florida State University, UCLA) used a novel ultrafast electron-beam-based technique sensitive to transient near fields at THz frequencies to observe a giant anisotropy in the linear optical response in Tungsten ditelluride (WTe2). They demonstrated that it is possible to tune THz polarization using a 50 […]
Tag Archives: Terahertz technology
Making ferromagnets ready for ultra-fast communication and computation technology
Phys.org June 14, 2024 Spin-torque driven critical spin dynamics, such as auto-oscillations, play the central role in many spin-based technologies. An international team of researchers (USA – UC Riverside, Johns Hopkins University, Germany, India, Ukraine) developed the theoretical framework of precessional auto-oscillations for ferromagnets with spin inertia. They discovered and introduced the concept of nutational auto-oscillations and demonstrated that they can become pivotal for future ultrahigh frequency technologies. They showed parallels between spin dynamics in ferrimagnets and inertial ferromagnets and derived an isomorphism that established a foundation for synergistic knowledge transfer between these research fields… read more. TECHNICAL ARTICLE
Physicists create optical component for 6G
Phys.org May 16, 2024 A new generation of diffractive components integrating specific geometry with additional features (flexibility, stretchability, rotation, and other approaches for tuning properties) extends the functionality of wavefront control. Researchers in Russia demonstrated an innovative approach to control the THz wavefront via a layered composition of spiral zone plates (SZPs) with tunable mutual orientation and scaling. As a proof of concept, they designed the SZP with experimental characterization of the resultant vortex beams. For each single SZP, a flexible element was proposed based on thin film of single-walled carbon nanotubes deposited on a stretchable substrate. The diffraction element […]
New type of tunable filter reveals the potential for terahertz wireless communications
Phys.org March 11, 2024 Researchers in Japan constructed a tunable Fabry–Perot interferometer (FPI) by controlling the effective refractive index of pitch-variable subwavelength gratings (PV-SWGs) that were incorporated into an FP cavity. The period of the PV-SWG could be varied to change the effective refractive index and shift the optical resonant frequency of the FPI. Compared with conventional methods that tune the optical resonance by adding fillers or deforming the cavity, the FPI obtained a higher transmission and quality factor (Q-factor) for the transmittance peak, and its resonant frequency could be shifted by simply stretching the PV-SWG. According to the researchers […]
Proposed metamaterial could have a wide range of applications, from sensing to stealth technology
Phys.org July 17, 2023 Materials scientists are actively hunting for metamaterials that are “perfect absorbers” of electromagnetic radiation with controllable resonance characteristics that lead to their wide usage in applications as varied as solar cells, thermal radiation imaging, sensing technology, and even stealth technology. An international team of researchers (Pakistan, USA – University of Alabama) has developed a triple-band perfect metamaterial absorber in terahertz regime that is made of asymmetric metallic I-shaped resonator and metallic ground layer with dielectric spacer in the middle. The simulated results showed that the absorption device had three resonance modes with corresponding absorption rate close […]
Unveiling the invisible: A breakthrough in spectroscopy to allow discoveries in materials physics
Phys.org June 12, 2023 Slow motion movies allow us to see intricate details of the mechanical dynamics of complex phenomena. If the images in each frame are replaced by terahertz (THz) waves, such movies can monitor low-energy resonances and reveal fast structural or chemical transitions. An international team of researchers (Canada, Germany) combined THz spectroscopy as a non-invasive optical probe with a real-time monitoring technique to demonstrate the ability to resolve non-reproducible phenomena at 50k frames per second, extracting each of the generated THz waveforms every 20 μs. Based on a photonic time-stretch technique to achieve unprecedented data acquisition speeds, […]
Capturing non-transparent ultrafast scenes
Phys.org May 26, 2023 Real-time imaging modalities with ultrahigh temporal resolutions are required for capturing ultrashort events on picosecond timescales for unveiling many fundamental mechanisms in physics, chemistry, and biology. Current single-shot ultrafast imaging schemes operate only at conventional optical wavelengths, being suitable solely within an optically transparent framework. Researchers in Canada leveraged the unique penetration capability of terahertz radiation to demonstrate a single-shot ultrafast terahertz photography system that could capture multiple frames of a complex ultrafast scene in non-transparent media with sub-picosecond temporal resolution. By multiplexing an optical probe beam in both the time and spatial-frequency domains, they encoded […]
Engineers develop a low-cost, quantum-dot-enhanced terahertz camera
Nanowerk November 5, 2022 The currently available THz detectors are limited in many aspects of their performance, including sensitivity, speed, bandwidth, and operating temperature. Most do not allow the characterization of THz polarization states. The recent observation of THz-driven luminescence in quantum dots offers a possible detection mechanism via field-driven interdot charge transfer. An international team of researchers (USA – MIT, University of Minnesota, , Stanford University, SLAC National Accelerator Laboratory, South Korea) has demonstrated a room-temperature CMOS THz camera and polarimeter based on quantum-dot-enhanced THz-to-visible upconversion mechanism with optimized luminophore geometries and fabrication designs. Besides broadband and fast responses, […]
Terahertz light from superconducting stripes
Phys.og September 22, 2022 The interplay between charge order and superconductivity remains one of the central themes of research in quantum materials. In the case of cuprates, the coupling between striped charge fluctuations and local electromagnetic fields is especially important, as it affects transport properties, coherence, and dimensionality of superconducting correlations. An international team of researchers (Germany, USA – Harvard University, Brookhaven National Laboratory, Switzerland, UK) studied the emission of coherent terahertz radiation in single-layer cuprates of the La2-xBaxCuO4 family, for which this effect is expected to be forbidden by symmetry. They found that emission vanishes for compounds in which […]
Emulating impossible ‘unipolar’ laser pulses paves the way for processing quantum information
Science Daily May 24, 2022 Key applications such as THz scanning tunnelling microscopy or electronic devices operating at optical clock rates call for ultimately short, almost unipolar waveforms, at megahertz (MHz) repetition rates. An international team of researchers (Germany, USA – University of Michigan) has developed a flexible and scalable scheme for the generation of strong phase-locked THz pulses based on shift currents in type-II-aligned epitaxial semiconductor heterostructures. The measured THz waveforms exhibit only 0.45 optical cycles at their centre frequency within the full width at half maximum of the intensity envelope, peak fields above 1.1 kV cm−1 and spectral components up […]