Katsumi Midorikawa

Bio: Katsumi Midorikawa is an academic researcher from University of Tokyo. The author has contributed to research in topics: Laser & Femtosecond. The author has an hindex of 59, co-authored 590 publications receiving 12112 citations. Previous affiliations of Katsumi Midorikawa include Saitama University.

Attosecond nonlinear optics using gigawatt-scale isolated attosecond pulses

Abstract: The short duration of attosecond pulses makes them interesting for ultrafast experiments, although it has so far been difficult to generate isolated attosecond pulses with sufficiently high power. Here the authors achieve high-intensity isolated attosecond pulses with a tabletop setup, based on a scaled-up high-order harmonic generation process.

Coherent water window x ray by phase-matched high-order harmonic generation in neutral media.

Abstract: We demonstrate the generation of a coherent water window x ray by extending the plateau region of high-order harmonics under a neutral-medium condition. The maximum harmonic photon energies attained are 300 and 450 eV in Ne and He, respectively. Our proposed generation scheme, combining a 1.6 microm laser driver and a neutral Ne gas medium, is efficient and scalable in output yields of the water window x ray. Thus, the precept of the design parameter for a single-shot live-cell imaging by contact microscopy is presented.

Control of the cross-sectional shape of a hollow microchannel embedded in photostructurable glass by use of a femtosecond laser

Abstract: Theoretical and experimental investigations have been made of the three-dimensional microchannel fabrication of photostructurable glass by use of a femtosecond (fs) laser. Generally, a microchannel fabricated inside glass by the scanning focal spot of a fs laser perpendicular to the direction of laser propagation assumes an elliptical shape with a cross section of large aspect ratio. We demonstrate that one can greatly reduce the aspect ratio merely by inserting a slit, which is oriented parallel to the laser’s scanning direction, before the focusing lens. Computer simulations show that a more symmetrical pattern is obtained in the vicinity of the focal point with the help of such a slit, owing essentially to a diffraction effect.

Microfluidic laser embedded in glass by three-dimensional femtosecond laser microprocessing.

Abstract: Microfluidic dye lasers three-dimensionally embedded in glass have been fabricated for what is believed to be the first time by integrating micro-optical and microfluidic components by use of a femtosecond laser. By pumping the microfluidic laser, in which the microfluidic chamber was filled with the laser dye Rhodamine 6G dissolved in ethanol, with a frequency-doubled Nd:yttrium aluminum garnet laser, lasing action was confirmed by analysis of the emission spectra at different pump powers. In addition, by arranging two microfluidic chambers serially in the glass, we built a microfluidic twin laser that produces an array of two simultaneous laser emissions with one pump laser.

Generation of highly coherent submicrojoule soft x rays by high-order harmonics

Abstract: We demonstrated the energy scaling of high-order harmonics using a self-guided beam under the phase-matched condition. By adjusting the argon gas density and pump laser focusing condition, a total output harmonic energy as high as $0.7 \ensuremath{\mu}\mathrm{J}$ was obtained in the spectral region of 34.8 to 25.8 nm (the corresponding order of the 23rd to 31st harmonic), while the 27th-order harmonic (29.6 nm) energy attained was as high as $0.3 \ensuremath{\mu}\mathrm{J}.$

A comprehensive review of zno materials and devices

Abstract: The semiconductor ZnO has gained substantial interest in the research community in part because of its large exciton binding energy (60meV) which could lead to lasing action based on exciton recombination even above room temperature. Even though research focusing on ZnO goes back many decades, the renewed interest is fueled by availability of high-quality substrates and reports of p-type conduction and ferromagnetic behavior when doped with transitions metals, both of which remain controversial. It is this renewed interest in ZnO which forms the basis of this review. As mentioned already, ZnO is not new to the semiconductor field, with studies of its lattice parameter dating back to 1935 by Bunn [Proc. Phys. Soc. London 47, 836 (1935)], studies of its vibrational properties with Raman scattering in 1966 by Damen et al. [Phys. Rev. 142, 570 (1966)], detailed optical studies in 1954 by Mollwo [Z. Angew. Phys. 6, 257 (1954)], and its growth by chemical-vapor transport in 1970 by Galli and Coker [Appl. Phys. ...

Deep tissue two-photon microscopy

Abstract: With few exceptions biological tissues strongly scatter light, making high-resolution deep imaging impossible for traditional⎯including confocal⎯fluorescence microscopy. Nonlinear optical microscopy, in particular two photon–excited fluorescence microscopy, has overcome this limitation, providing large depth penetration mainly because even multiply scattered signal photons can be assigned to their origin as the result of localized nonlinear signal generation. Two-photon microscopy thus allows cellular imaging several hundred microns deep in various organs of living animals. Here we review fundamental concepts of nonlinear microscopy and discuss conditions relevant for achieving large imaging depths in intact tissue.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

Abstract: A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Femtosecond laser micromachining in transparent materials

Abstract: Femtosecond laser micromachining can be used either to remove materials or to change a material's properties, and can be applied to both absorptive and transparent substances. Over the past decade, this technique has been used in a broad range of applications, from waveguide fabrication to cell ablation. This review describes the physical mechanisms and the main experimental parameters involved in the femtosecond laser micromachining of transparent materials, and important emerging applications of the technology. Interactions between laser and matter are fascinating and have found a wide range of applications. This article gives an overview of the fundamental physical mechanisms in the processing of transparent materials using ultrafast lasers, as well as important emerging applications of the technology.