Laser-induced fine structures on silicon exposed to THz-FEL

We found the irradiation of focused linearly polarized terahertz (THz)-waves emitted from THz free-electron laser (THz-FEL) engraved fine periodic stripe structures on the surfaces of single-crystal Si wafers. The experiments were performed at several wavelengths ranging from 50 to 82 μm with a macro-pulse fluence up to 32 J/cm2. The engraved structures are considered equivalent to the laser-induced periodic surface structures (LIPSS) produced by the irradiation of a femtosecond (fs)-pulsed laser in the near-infrared (NIR) region. However, the minimum period of ∼1/25 of the wavelength in the present case of THz-FEL is surely much smaller than those reported so far by use of fs-lasers and no more explicable by the so far proposed mechanisms. The finer LIPSS confirmed by longer-wavelength laser excitation by means of THz-FEL motivates investigation into the universal mechanism of LIPSS formation, which has been under a hot debate for decades

Spatially Resolved Spectral Imaging by A THz-FEL

Using the unique characteristics of the free-electron-laser (FEL), we successfully performed high-sensitivity spectral imaging of different materials in the terahertz (THz) and far-infrared (FIR) domain. THz imaging at various wavelengths was achieved using in situ spectroscopy by means of this wavelength tunable and monochromatic source. In particular, owing to its large intensity and directionality, we could collect high-sensitivity transmission imaging of extremely low-transparency materials and three-dimensional objects in the 3–6 THz range. By accurately identifying the intrinsic absorption wavelength of organic and inorganic materials, we succeeded in the mapping of spatial distribution of individual components. This simple imaging technique using a focusing optics and a raster scan modality has made it possible to set up and carry out fast spectral imaging experiments on different materials in this radiation facility

High- and Low-Energy Photoemission Study of Strongly Correlated Au–Ga–Ce Quasicrystal Approximants: Localized 4f Nature and Disorder Effects

Nozue G., Fujiwara H., Hamamoto S., et al. High- and Low-Energy Photoemission Study of Strongly Correlated Au–Ga–Ce Quasicrystal Approximants: Localized 4f Nature and Disorder Effects. Journal of the Physical Society of Japan 93(7) 074601, 15 July, 2024; https://doi.org/10.7566/JPSJ.93.074703.We have investigated the electronic structures of Ce-based 1/1 quasicrystal approximants Au₅₉.₂Ga₂₅.₇Ce₁₅.₁ and Au₆₀.₃Ga₂₆.₁Ce₁₃.₆ by hard X-ray photoemission (HAXPES) and high-resolution photoemission spectroscopy. The localized Ce 4f electronic states are revealed for both Au–Ga–Ce approximants. Moreover, disorders in the compounds notably affect their electronic states, which has been detected by the core-level HAXPES. Valence-band photoemission spectra show the slight spectral difference depending on the composition ratio, which can be explained by a rigid-band-like shift

Hole Doping Effects on Physical Properties of the Layered Antiferromagnetic Insulator (LaO)MnPn (Pn=P, As, Sb)

AbstractWe have investigated an insulating origin of the layered Mn oxypnictide (LaO)MnPn with half-filled Mn 3d bands by choosing pnictogen atoms from P to Sb and introduction of hole carriers. Metallic states are found in (LaO)MnAs and (LaO)MnSb at higher hole doping

Spatially resolved spectral-imaging by a THz-FEL

Using the unique characteristics of the free-electron-laser (FEL), we successfully performed high-sensitivity spectral-imaging of different materials in the terahertz (THz) and far-infrared (FIR) domain. THz imaging at various wavelengths was achieved using in-situ spectroscopy by means of this wavelength tunable and monochromatic source. In particular, owing to its large intensity and directionality we could collect high-sensitivity transmission imaging of extremely low-transparency materials and three-dimensional objects in the 3-6 THz range. By accurately identifying the intrinsic absorption wavelength of organic and inorganic materials, we succeeded in the mapping of spatial distribution of individual components. This simple imaging technique using a focusing optics and a raster scan modality has made it possible to set up and carry out fast spectral-imaging experiments on different materials in this radiation facility