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: S&T Japan
Paper AI sensor mimics brain for health monitoring
Nanowerk March 11, 2024 Physical reservoir computing (PRC), which mimics the human brain using physical phenomena, offers a low-power consumption architecture. However, creating a flexible and easily disposable sensors using PRC capable of processing optical signals with sub-second response times suitable for biological signals presents a challenge. Researchers in Japan designed disposable and flexible paper-based optoelectronic synaptic devices which are composed of nanocellulose and ZnO nanoparticles, for PRC. The device exhibited synaptic photocurrent in response to optical input. The memory capacity of short-term memory task, indicating the device’s ability to store past information was 1.8. It could recognize handwritten digits […]
Light stimulates a new twist for synthetic chemistry
Nanowerk February 28, 2024 Photoinduced concerted multiple-bond rotation has been proposed in some biological systems. However, the observation of such phenomena in synthetic systems has been a challenge in the photochemistry field. Researchers in Japan described a chalcogen-substituted benzamide system that exhibits photoinduced dual bond rotation in heteroatom-containing bonds. Introduction of the chalcogen substituent into a sterically hindered benzamide system provided sufficient kinetic stability and photosensitivity to enable the photoinduced concerted rotation. The presence of two different substituents on the phenyl ring in the thioamide derivative enabled the generation of a pair of enantiomers and E/Z isomers. Using these four […]
Coordination polymer crystals show promise as new generation of light sources for industry, medicine
Phys.org February 20, 2024 Luminescent lanthanide coordination polymer crystals (LCPCs) provide a high level of structural tunability, including size- and morphology-dependent properties; therefore, they are promising materials for next-generation phosphors in a wide range of applications such as light emitting diodes. By controlling the morphology of thermostable europium coordination polymer crystals researchers in Japan developed a novel red phosphor with narrow linewidth emission and characterized them through analysis. Size tunable crystalline polymer spheres had high internal quantum efficiency and high thermostability, and exhibited dispersibility in PMMA Poly(methyl methacrylate) media… read more. Open Access TECHNICAL ARTICLE
Researchers solve a foundational problem in transmitting quantum information
Phys.org February 13, 2024 To investigate light-matter hybrid excitations in a quantum dot (QD) THz resonator coupled system researchers in Japan fabricated a gate-defined QD near a THz split-ring resonator (SRR) by using a AlGaAs/GaAs two-dimensional electron system. By illuminating the system with THz radiation, the QD showed a current change whose spectrum exhibited coherent coupling between the electrons in the QD and the SRR as well as coupling between the two-dimensional electron system and the SRR. The latter coupling entered the ultrastrong coupling regime and the electron excitation in the QD also exhibited coherent coupling with the SRR with […]
Communing with nothingness
Nanowerk November 6, 2023 Light–matter interaction in the ultrastrong coupling regime is attracting considerable attention owing to its applications to coherent control of material properties by a vacuum fluctuation field. However, electrical access to such an ultra-strongly coupled system is very challenging. Researchers in Japan have fabricated a gate-defined quantum point contact (QPC) near the gap of a terahertz (THz) split-ring resonator (SRR) fabricated on a GaAs two-dimensional (2D) electron system. By illuminating the system with external THz radiation, the QPC showed a photocurrent spectrum which exhibited significant anticrossing that came from coupling between the cyclotron resonance of the 2D […]
Optical-fiber based single-photon light source at room temperature for next-generation quantum processing
Science Daily November 2, 2023 Rare-earth (RE) atoms in solid-state materials are attractive components for photonic quantum information systems because of their coherence properties even in high-temperature environments. Researchers in Japan performed the single-site optical spectroscopy and optical addressing of a single RE atom in an amorphous silica optical fiber at room temperature. The single-site optical spectroscopy of the tapered RE-doped fiber showed nonresonant emission lines similar to those seen in the case of an unstructured fiber and the autocorrelation function of photons emitted from the fiber showed the antibunching effect due to the spatial isolation given by the tapered […]
Cathode active materials for lithium-ion batteries could be produced at low temperatures
Science Daily October 23, 2023 Layered LiCoO2 is usually synthesized after a prolonged sintering process at high temperatures for 10–20 h. Researchers in Japan have developed a “hydroflux process” to obtain highly crystalline and layered LiCoO2 at a low temperature within 30 min. They found that the molten mixed hydroxide-containing water molecules significantly accelerated the formation of LiCoO2, which showed a highly reversible capacity of 120 mAh g–1 without post annealing. The reaction mechanism study showed fast growth of LiCoO2 crystals suggesting that the excess molten hydroxides containing water dissolved the cobalt species of HCoO2 and suppressed the competing reaction […]
Move over carbon, the nanotube family just got bigger
Phys.org October 16, 2023 Single-walled TMD nanotubes (SW-TMDNTs) are 1D materials that can exhibit tunable electronic properties depending on both their chirality and composition. However, much less has been explored about their geometrical structures and chemical variations due to their instability under ambient conditions. Researchers in Japan have shown that the outer surfaces and inner cavities of the BNNTs promote and stabilize the coaxial growth of SW-TMDNTs with various diameters, including few-nanometers-wide species. The chiral indices of individual SW-MoS2NTs were assigned by high-resolution transmission electron microscopy, and statistical analyses revealed a broad chirality distribution ranging from zigzag to armchair configurations. […]
Successful optical biosensing using dual optical combs: High sensitivity and rapid detection of biomolecules
Phys.org September 26, 2023 Rapid, sensitive detection of biomolecules is important for biosensing of infectious pathogens as well as biomarkers and pollutants. Researchers in Japan have achieved rapid and sensitive detection of SARS-CoV-2 nucleocapsid protein antigen by enhancing the performance of optical biosensing based on optical frequency combs (OFC). The virus-concentration-dependent optical spectrum shift produced by antigen–antibody interactions was transformed into a photonic RF shift by a frequency conversion between the optical and RF regions in the OFC, facilitating rapid and sensitive detection with well-established electrical frequency measurements. The active-dummy temperature-drift compensation with a dual-comb configuration enabled the very small […]