Hiroharu Kawasaki

980 nm Bi3Fe5O12/Sm3Ga5O12 magneto-optical photonic crystal

Heteroepitaxial all-garnet magneto-optical photonic crystal (MOPC) was fabricated to enhance Faraday rotation at 980nm. MOPC was composed of alternating MO-active Bi3Fe5O12 and transparent Sm3Ga5O12 quarter-wavelength layers grown by rf-magnetron sputtering on Ca,Mg,Zr:Gd3Ga5O12(111) single crystal substrate. High MO performance at the resonance wavelength λ=980nm, specific Faraday rotation θF=−7.3°∕μm, absorption coefficient α=3350cm−1, and MO figure of merit Q=2∣θF∣∕α=43.6° demonstrates feasibility to use bismuth iron garnet MOPCs for application in pump laser diodes, optical amplifiers, modulators, and sensors.

TiO2/TiN/TiO2 heat mirrors by laser ablation of single TiN target

Titanium oxide (TiO2 ) and titanium nitride (TiN) multilayered films grown by pulsed laser deposition (PLD) technique have been tested as a heat mirror, which have a high transmittance in the visible region and a high reflectance in the infrared. Three layer TiO2 /TiN/TiO2 heat mirrors were grown on Corning glass substrates ablating single TiN target. Switching of TiO2 -to-TiN layers composition was achieved by changing gas atmosphere (oxygen-to-nitrogen). Grown TiO2 /TiN/TiO2 heat mirrors are highly transparent in visible (above 60% at 525nm), opaque in infrared (10% at 2600nm) and in the range from 400 nm to 2600 nm they possess almost the same properties as films prepared using two targets: TiO2 and TiN. XPS confirms similarity of chemical composition of multilayered TiO2 /TiN films prepared by single TiN and two TiO2 and TiN targets techniques. Furthermore, multifunctional self cleaning properties of TiO2 /TiN heat mirrors are expected through the precise control of the composition of the top TiO2 layer operating as a photocatalyst.

Tailoring optical properties of pulsed laser deposited TiO2 films

The paper is dedicated to the investigation into optical properties of TiO2 thin films pulsed laser deposited at the temperature as low as 150 degrees C and subjected to the following heat treatmen ...

Effect of Oxygen Gas Pressure on Electrical, Optical, and Structural Properties of Al-Doped ZnO Thin Films Fabricated by Pulsed Laser Deposition for Use as Transparent Electrodes in All-Solid-State Electrochromic Devices

Low-resistivity and high-transmittance Al-doped ZnO (AZO) thin films were obtained by pulsed laser deposition with the substrate at room temperature. The electrical, optical, and structural properties of the AZO thin films deposited at various oxygen gas pressures (PO2) were investigated. X-ray diffraction shows that the AZO thin films have (002) preferred orientation and the diffraction angle of the (002) plane shifts to a higher value with increasing oxygen gas pressure. All AZO thin films deposited under ambient oxygen gas pressure conditions have an optical transmittance of over 80% in the visible region. AZO thin films deposited at lower PO2 of ≤1 Pa have resistivities of 1 Pa. The AZO film deposited at PO2 = 1 Pa had the lowest resistivity (5.8 ×10-4 Ω cm) with a high carrier concentration of 1.1 ×1021 cm-3.

Gas flow dependence on dynamic behavior of serpentine plasma in gliding arc discharge system

Gliding arc discharge systems have been used in various applications. However, the power of conventional gliding arc plasmas is relatively high and the system requires an additional discharge for its ignition and a resistor for current protection, which causes further total energy consumption. We have proposed ultraviolet (UV)-assisted gliding arc discharge systems supported by time-resolved understanding for electrical characteristics and dynamic behavior of serpentine plasmas. In this paper, we report on gas flow dependence on dynamic behavior of serpentine plasmas in a gliding arc discharge system with the irradiation of a low-pressure mercury lamp. Time-resolved evaluation was carried out using the results of synchronized measurement for serpentine plasmas with a high-speed camera, a high-voltage probe, and a current sensor. Waveforms and mean values of the applied voltage, current, power, impedance, and energy for serpentine plasmas in the UV-assisted gliding arc discharge system were studied. The power and impedance per unit plasma length were also evaluated.

Plasma Processing of Functional Thin Films by Sputtering Deposition Using Metal-Based Powder Target

Titanium-based functional thin films were prepared by a sputtering deposition method using a metal powder target, and the electron density and temperature of the processing plasma were investigated. The electron density of the plasma, measured by a probe method, when using a powder target was higher than that when using a bulk target. The deposition rate when using a powder target was also higher than that in the case of a bulk target. These results may be due to the net-cathode area of the powder target being larger than that of the bulk target. X-ray photoelectron spectroscopy, X-ray diffraction measurements, and atomic force microscopy images of the films prepared using the Ti powder target indicated nearly the same properties as those of films prepared using a Ti bulk target, and the prepared films are oxide. These results suggest that TiO2 thin films can be prepared using a Ti powder target and that the quality is almost the same as those of films prepared using a Ti bulk target.

Synthesis of Platinum Nanodots Using Organ-Metal Solutions

In this study, platinum (Pt) nanodots with diameters of 73–142 nm were prepared using organ-metal solutions on silicon substrates by a heating process. The influence of heating conditions such as heating temperature and ambient gas pressure on the structural properties of the Pt nanodots was investigated. The size and shape of the Pt nanodots were measured using scanning electron microscopy and image analysis software. The results suggest that the diameter and shape of the Pt nanodots can be controlled by heating temperature. In addition, X-ray diffraction and X-ray photoelectron spectroscopy measurement results suggest that the crystallinity and atomic composition of the Pt nanodots can also be controlled by varying ambient gas pressure. Changing the ambient gas pressure while maintaining a constant temperature affected the growth of Pt and platinum silicide (PtSi) crystals in the Pt nanodots. Under atmospheric pressure and an ambient Ar pressure of 5000 Pa, a single Pt crystal was formed in the Pt nanodots. On the other hand, under low vacuum and an ambient Ar pressure of 700 Pa, Pt and PtSi crystals coexisted in the Pt nanodots.

Fundamental studies on effect of ozone injection to the internal-combustion engine - FTIR spectrum of hydrocarbon compound reformulated by ozone

The mixture gas composed of hydrocarbon compounds and air/O2 exposed to discharge was analysed by FTIR. The emission spectroscopy of combustion in the enriched condition of O2 and O3 was not very different because it was assumed that the consumption of O atoms required for combustion was consistent. The spectrum around 1750 cm-1 of the mixture gas, which did not appear before discharge, was detected by FTIR. The generation rate of the by-product around 1750 cm-1 strongly relates with O3 concentration. It was suggested that O3 is the major molecule reacting with vaporised hydrocarbon compounds. A candidate for the by-product was supposed to be C8H16O or/and C8H16O2 from the reference absorption spectra of FTIR. The by-product was produced with thin O3 concentration, which was 0.62 g/m3 in the test, although O3 was emitted as extra when injected O3 was more than approximately 2 g/m3.

Discharge characteristics in liquid helium, liquid nitrogen and pure water preparatory to fabrication of carbon nanomaterials

Discharge characteristics and emission spectra of the discharges in low-temperature liquid such as liquid helium have been measured to investigate the conditions for fabrication of carbon nanomaterial by arc discharge in low-temperature liquid. Measurements of the discharge characteristics of the resulting plasma and observation of the associated optical emission spectra show that the behaviour of discharge current over time and the associated spectra depend strongly on discharge voltage and both may be related to the temperature of the carbon target. However, discharge voltage and current with time are almost the same regardless of whether the liquid is pure water, liquid nitrogen, liquid helium and superfluid liquid helium