Yuuki Uesugi

Tight focusing of a radially polarized beam is used for single-shot laser ablation of metals. The strong longitudinal field is generated at the focus, and its contribution to the ablation process is comprehensively examined for various metal materials. In the presence of the longitudinal field at the focus, a fabricated crater at the surface exhibits either a spot shape or a doughnut shape, depending on the material. The experimental results indicate that the strong longitudinal electric field o

Acne agminata (lupus miliaris disseminatus faciei), once regarded as a tuberculide, is a facial granulomatous disease still seen in young adults in Japan, despite a decrease in the incidence of tuberculosis. Although most lesions regress within a few years, even without treatment, disfiguring scars remain on the face. We have evaluated the efficacy of low dose oral prednisone therapy because, in the past, there has been no satisfactory therapy for this condition. We have treated four patients wi

The creation of ultraviolet optical vortex beams with the topological charge of $ \vert l \vert = 1 $|l|=1 at the wavelength of 325 nm was demonstrated from a He-Cd metal vapor laser with a spot defect mirror. The measured $ {{\rm M}^2} $M² factor was close to the theoretical value of two of the $ {{\rm LG}_{01}} $LG₀₁ Laguerre-Gaussian mode. Some interference experiments showed that the obtained vortex beams were stable enough for practical applications such as holographic

The interaction of electrons with a cylindrically distributed optical standing wave has not attracted much attention, despite its suitability for electron-optical imaging systems. This study shows that the action of a round lens for electrons is provided by a tightly focused, cylindrically polarized Bessel-Gauss (BG) beam. Here an azimuthally polarized BG beam acts as a convex lens with a negative (opposite sign) spherical aberration, compared to conventional electrostatic or magnetic round lens

We demonstrate the femtosecond-laser processing of self-suspended monolayer graphene grown by chemical vapor deposition, resulting in multipoint drilling with holes having a diameter of <100 nm. Scanning transmission electron microscopy revealed the formation of many nanopores on the laser-irradiated graphene. Furthermore, atomic-level defects as well as nanopores were found in the graphene membrane by high-resolution transmission electron microscopy, while the overall crystal structure remained

Abstract The properties of electron round lenses produced by the ponderomotive potential are investigated in geometrical optics. The potential proportional to the intensity distribution of a focused first-order Bessel or Laguerre–Gaussian (LG) beam is exploited to produce an electron round lens and a third-order spherical aberration (SA) corrector. Several formulas for the focal length and SA coefficients in the thin-lens approximation are derived to set the lens properties and associated light

Abstract In this study, femtosecond laser-based multi-beam interference laser processing on nanofilms with nanometer thicknesses was demonstrated. The resulting multi-hole, two-dimensional lattice pattern reflected a laser interference fringe formed on the surface of the nanofilm, with no breaks or cracks. In anticipation of the actual nanostructure fabrication, additional laser processing was performed to drill additional holes in the spaces between the existing holes, resulting in high-density

Ultrafast laser ablation was applied to process 10-nm self-supporting membranes. The membranes were processed over tens of square micrometers by single-shot irradiation of two visible laser pulses, followed by the realization of periodic sub-microstructures. The fabricated geometry is dependent on the intensity distribution of the superposed input pulses, providing flexibility and facilitating practical micro- and nanoengineering. Ease of designing the processing parameters and speed of processi

We demonstrated the operation of a high finesse optical cavity without utilizing an active feedback system to stabilize the resonance. The effective finesse, which is a finesse including the overall system performance, of the cavity was measured to be 394 000 ± 10 000, and the laser power stored in the cavity was 2.52 ± 0.13 kW, which is approximately 187 000 times greater than the incident power to the cavity. The stored power was stabilized with a fluctuation of 1.7%, and we confirmed continuo

Recently, electron beams with structured phase fronts, such as electron vortex beams, have attracted considerable interest. Herein, we present a novel method of fabricating electron phase holograms using a femtosecond laser interference processing. A 35-nm-thick silicon membrane, corresponding to a phase shift of π for 200-keV electrons, was processed using single-shot laser irradiation, whereas processing such thin membranes with a focused ion beam milling technique would be very difficult. Thi

In this paper, we demonstrated the processing of free-standing thin films by the ultrafast laser ablation, which has been difficult to process using existing nanoprocessing methods such as focused ion beam milling. First, we fabricated a holographic diffraction grating for transmission electron microscopy using a two-beam interference laser processing. We fabricated an electron phase hologram made of silicon with a thickness of 35 nm that generated electron vortex beams with high efficiency. The

Systemic measures to control recalcitrant pruritus observed in many patients with chronic renal failure receiving dialysis are generally unsatisfactory. We evaluated the efficacy of treatment of uremic pruritus with longwave ultraviolet irradiation (UVA) in conjunction with topical psoralen application (PUVA) in 13 patients with chronic renal failure and severe pruritus which was not attributed to other skin or internal disease. The patients received 1 to 12 treatments to the entire skin surface

Electron phase hologram was fabricated by a single-shot femtosecond laser interference processing. The generation of electron vortices from the fabricated hologram was demonstrated with higher diffraction efficiency than that of amplitude hologram as expected.