Phys.org November 6, 2023 Existing terahertz inspection systems face throughput and accuracy restrictions due to their limited imaging speed and resolution. Furthermore, machine-vision-based systems using large-pixel-count imaging encounter bottlenecks due to their data storage, transmission, and processing requirements. Researchers at UCLA developed a diffractive sensor that rapidly detects hidden defects/objects within a 3D sample using a single-pixel terahertz detector, eliminating sample scanning or image formation/processing. Using deep-learning-optimized diffractive layers, the diffractive sensor could all-optically probe the 3D structural information of samples by outputting a spectrum, and directly indicated the presence/absence of hidden structures or defects. They experimentally validated this framework […]
Category Archives: Terahertz technology
Widely tunable terahertz lasers boost photo-induced superconductivity in K₃C₆₀
Phys.org October 12, 2023 Photoexcitation at terahertz and mid-infrared frequencies has emerged as an effective way to manipulate functionalities in quantum materials, in some cases creating non-equilibrium phases that have no equilibrium analogue. In K3C60, a metastable zero-resistance phase was observed that has optical properties, nonlinear electrical transport, and pressure dependencies compatible with non-equilibrium high-temperature superconductivity. An international team of researchers (Germany, Switzerland, Italy, UK) demonstrated a two-orders-of-magnitude increase in photo-susceptibility near 10 THz excitation frequency. At these drive frequencies, a metastable superconducting-like phase was observed up to room temperature. The discovery of a dominant frequency scale sheds light on the […]
Ultrafast and tunable: Graphene-based terahertz-to-visible light conversion
Nanowerk, June 15, 2023 Several technologies could benefit from the availability of fast and controllable conversion of terahertz light to visible light. An international team of researchers (Germany, Spain, UK) demonstrated that the exceptional properties and dynamics of electronic heat in graphene allow for a THz-to-visible conversion, which is switchable at a sub-nanosecond time scale. They showed a tunable on/off ratio of more than 30 for the emitted visible light, achieved through electrical gating using a gate voltage on the order of 1 V and that a grating-graphene metamaterial leads to an increase in THz-induced emitted power in the visible […]
Hybrid bound states in the continuum in terahertz metasurfaces
Phys.org May 26, 2023 The most common strategy to apply bound states in the continuum (BICs) in a metasurface is by breaking symmetry of resonators in the uniform array that leaks the otherwise uncoupled mode to free space and exhibits an inverse quadratic relationship between quality factor (Q) and asymmetry. Researchers in China have proposed a scheme to further reduce scattering losses and improve the robustness of symmetry protected BICs by decreasing the radiation density with a hybrid BIC lattice. They observed a significant increase of radiative Q in the hybrid lattice compared to the uniform lattice. In the hybrid […]
Researchers observe extremely squeezed directional THz waves in thin semiconductor crystals
Phys.org May 4, 2023 Thin layers of in-plane anisotropic materials can support ultra confined polaritons, whose wavelengths depend on the propagation direction. Such polaritons hold potential for the exploration of fundamental material properties and the development of novel nanophotonic devices. However, the real-space observation of ultra confined in-plane anisotropic plasmon polaritons (PPs)—which exist in much broader spectral ranges than phonon polaritons—has been elusive. An international team of researchers (Spain, China, Czech Republic, UK, Germany) imaged and analyzed THz waves that propagate in the form of plasmon polaritons along thin anisotropic semiconductor platelets with wavelengths reduced by up to 65 times […]
Approaching the terahertz regime
Science Daily January 19, 2023 Tunnelling magnetoresistance (TMR) is considered to be proportional to spin polarization at the interface and has been studied primarily in ferromagnets. An international team of researchers (Japan, Canada) observed TMR in an all-antiferromagnetic tunnel junction consisting of Mn3Sn/MgO/Mn3Sn. They made measurements using a Fe/MgO/Mn3Sn MTJ and showed that the sign and direction of anisotropic longitudinal spin-polarized current in the antiferromagnet can be controlled by octupole direction. They measured a TMR ratio of around 2% at room temperature, which arises between the parallel and antiparallel configurations of the cluster magnetic octupoles in the chiral antiferromagnetic state. […]
Anti-correlated plasma and THz pulse generation during two-color laser filamentation in air
Phys.org September 9, 2022 The THz generation efficiency and the plasma density generated by a filament in air have been found anti-correlated when pumped by two-color laser field. The plasma density near zero delay of two laser pulses has a minimum value, which is opposite to the trend of THz generation efficiency and contradicts common sense. The lower plasma density cannot be explained by the static tunneling model according to the conventional photocurrent model, but it might be attributed to the electron trapping by the excited states of nitrogen molecule. An international team of researchers (China, Japan) clarified the dominant […]
New theory for detection of terahertz electromagnetic waves gives hope for advances in IT and medicine
Phys.org September 2, 2022 An international team of researchers (Germany, UK) has presented a detailed theory of the in-plane photoelectric (IPPE) effect providing analytical results for the THz wave generated photocurrent, the quantum efficiency, and the internal responsivity of the detector, the gate voltages, and the geometrical parameters of the detector. The calculations are performed for macroscopically wide samples at zero temperature. Results of the theory are applicable to any semiconductor systems with 2D electron gases, including III-V structures, silicon-based field effect transistors, and the novel 2D layered, graphene-related materials. Their findings make it possible to construct small, inexpensive, and […]
Wallet-sized device focuses terahertz energy to generate high-resolution images
EurekAlert February 18, 2022 Researchers at MIT have built the most precise, electronically steerable, terahertz antenna array, called “reflectarray” which contains nearly 10,000 antennas onto a device the size of a credit card. It can precisely focus a beam of terahertz energy on a tiny area and control it rapidly with no moving parts. The researchers demonstrated the device by generating 3D depth images with military-grade resolution and twice the angular resolution of those produced by a large radars. The new phase shifter design consumes no power at all. The reflectarray uses one main source of energy to fire terahertz […]
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 […]