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 […]
Tag Archives: Terahertz technology
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 […]
Scientists turn a hydrogen molecule into a quantum sensor
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 […]
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 […]