Atmospheric-pressure low-temperature plasma jets, widely employed in diverse applications, appear jet-like due to the repeated high-speed propagation of localized discharges known as plasma bullets, rather than by simple downstream gas flow. These plasma bullets give rise to unique phenomena distinct from conventional jets. This paper first outlines the fundamental properties of plasma bullets and then describes phenomena in which a plasma jet appears to tunnel through a dielectric wall, as well as the generation of surface-launched plasma bullets that are launched like rockets from a planar dielectric surface. Applications of these phenomena to hydrophilic modification of continuous porous dielectrics are discussed, along with ongoing efforts toward realizing large-volume atmospheric-pressure low-temperature plasmas, which have yet to be achieved.

Superconducting nano-strip photon detectors are being applied to a wide range of advanced photonics technologies, including quantum technology, due to their excellent photon detection performance. However, the fabrication of superconducting nanostrips with a width of around 100 nm requires advanced nano fabrication technology, making it difficult to mass-produce high-performance detectors. We have achieved high-performance operation of a superconducting wide-strip photon detector with a width more than 200 times wider than conventional nanostrips by introducing a novel superconducting strip structure that focuses on the bias current distribution within the superconducting strip. Our detector is expected to contribute to the development of various scientific and technological fields, including the scaling up of quantum technology, as a high-performance and mass-producible photon detector.

We developed a frequency up-conversion single-photon detector based on the quantum pulse gate method and demonstrated femtosecond time-resolved time-of-flight (ToF) measurements with strong temporal-mode selectivity in the 1550 nm band. When applied to optical tomography of a mouse brain, the ToF technique yielded clear cross-sectional images. With a probe beam power of 1.5 mW in average, the system achieved a sensitivity exceeding 110 dB and an axial resolution of 57 μm (refractive index: 1.37). This approach provides a promising alternative for non-contact, non-invasive three-dimensional structural imaging, which is essential in biological, medical, and industrial applications.

It is expected that applying magnetic fields to processing plasmas would extend the plasma controllability with novel value-added functions. Electron motion that governs the response and structure of processing plasmas become complicated under the actions of both electric and magnetic fields. Therefore, understanding of the fundamental effects of magnetic fields on electrons based on theoretical and numerical studies are important for advanced design and control of plasma equipment. This article presents an overview on elementary electron behaviors under electric and magnetic fields and introduces investigations on interesting functional effects of magnetic fields with specific arrangements by particle simulations.

The study of electrochemical conversion of atmospheric CO2 into value-added products has been attracting attention since the 1970s. Early investigations revealed a wide distribution of reduced carbonaceous species derived from copper (Cu) metal cathodes. Since the zero-gap-type reactors operate at relatively low full-cell voltages and high current densities, extensive research has been conducted on systems combining Cu cathodes with zero-gap configurations. This article provides a comprehensive overview of the historical development of electrochemical CO2 reduction. Furthermore, it addresses key challenges for enhancing long-term operational durability associated with the zero-gap-type reactor, and the phenomena of flooding and salt precipitation at the cathode are clarified.

Circularly polarized light (CPL) carries diverse information, such as birefringence and stress distribution in materials, that cannot be distinguished by the human eye. In this study, we aim to achieve highly sensitive CPL detection by developing crystalline thin films with one-dimensional (1D) helical structures, created through the hybridization of organic chiral molecules and inorganic semiconductors, as well as corresponding photodetectors. For example, lead halide perovskites, through interaction with organic chiral molecules, can acquire a 1D helical structure, exhibiting an exceptionally strong circular dichroism of up to 5000 mdeg. Furthermore, by employing these 1D helical crystalline thin films as the photoactive layer, we successfully fabricated photodetectors capable of selectively detecting the handedness of CPL. This represents the first demonstration of direct CPL detection utilizing a helical structure and achieves the highest sensitivity reported for CPL photodetectors.

The power semiconductor device industry remains a domain in which Japan retains a strong competitive edge within the global market. Today, silicon-based semiconductors dominate this field, holding an overwhelming market share. However, in recent years, silicon carbide (SiC) and gallium nitride (GaN) semiconductor devices have gradually emerged as increasingly prominent technologies, gaining recognition as viable commercial products.

This lecture will provide a comprehensive and accessible overview of the latest advancements in next-generation power semiconductor devices—technologies that are indispensable for realizing more efficient utilization of electrical energy. Particular emphasis will be placed on SiC and GaN power semiconductor devices, which are expected to experience significant growth in demand shortly.