Kohei Kadono

Gold nanoparticles ion implanted in glass with enhanced nonlinear optical properties

Silica glass with dispersed colloid Au particles was synthesized by ion implantation. Colloid Au particles were found to grow through an Ostwald ripening mechanism controlled by diffusion in the silica glass. The third‐order nonlinear optical susceptibility χ(3) of this glass was found to be proportional to the fourth power of the radius of the colloid particles or the fourth power of the absorption coefficient at the peak of a plasmon band when the total volume of the colloid particles was constant. Furthermore, χ(3) of the glass was inversely proportional to the third power of the total volume of colloid particles when the absorption coefficient of the plasmon band was constant.

Judd–Ofelt parameters and multiphonon relaxation of Ho3+ ions in ZnCl2-based glass

Spectroscopic properties of Ho3+-doped ZnCl2-based glasses are investigated. The Ω2 value of the glass is especially large compared with those in fluoride glasses while the Ω4 and Ω6 parameters are relatively small. Decay measurements for three excited states 5F5, 5S2+5F4, and 5F2,3+3K8 were performed and multiphonon relaxation (MPR) rates of the respective states were estimated. The experimental data are approximately on a line expressed by WMPR=C exp(−αΔE) with C=5.0×107 s−1 and α=4.0×10−3 cm. The host-dependent constant C is very small, contributing to high quantum efficiencies of emissions. The Ho3+ concentration dependence of the fluorescence lifetime of the 5F5 and 5S2+5F4 levels was also investigated. The concentration quenching of the 5S2+5F4 level can be explained by the cross-relaxation mechanism: 5S2→5I4 and 5I7←5I8 transitions.

Preparation and optical property of monolithic silica gel uniformaly dispersed with gold colloid from aqueous solution

Abstract Gold colloids were prepared from aqueous HAuCl4 solutions ranging in concentration from 0.01 to 0.05 wt% by reducing with sodium citrate and dispersed in a monolithic disk, with 35 mm diameter and 1 mm thickness, by the sol-gel method. Tetramethoxysilane is the only useful reagent as Si source. The particle size of dispersed gold colloids was about 50 nm. This silica gel had a third-order optical non-linearity and its susceptibility, χ(3), was about 7×10−12 esu.

Formation of Au Colloid Particles in Silica Glass by Ion Implantation.

Formation of Au colloid particles and their optical property have been investigated in silica glasses implanted with Au + ions at an acceleration energy of 1.5MeV and fluence levels of 10 16 -10 17 ions/cm 2 . The Au colloid particles are formed in the as-implanted glasses. It is inferred that the average radius of Au colloid particles depends on the fluence level, although the fluence level does not affect the distribution of Au atomic concentration. The heat-treatment little affects the Au atomic distribution. The Au colloid particles grow to 4.3nm in average radius during heat treatment. It is revealed that the large nonlinear optical property of the Au + -ion-implanted silica glass is attributed to the high concentration of the Au colloid particles in the narrow region.

Raman spectroscopic study on the structure of ZnCl2ZnX2 and ZnCl2KX (X = Br, I) glasses

Abstract Raman spectra have been measured for ZnCl 2 ZnX 2 and ZnCl 2 KX (X = Br, I) glasses to investigate the structure of the glasses with varying composition. The assignment of each band was made, and the change of the spectra with composition was explained in terms of the bridging and non-bridging states of halide ions and the change of the tetrahedral units, ZnX n Cl 4− n 2− ( n = 0–4), formed in the glasses. As the content of ZnX 2 in ZnCl 2 ZnX 2 glasses increases (20 → 80 mol%), the peak frequency of the ZnCl stretching mode increases (238 → 248 cm −1 in X = I glasses, 238 → 259 cm −1 in X = Br glasses) while the ZnI and ZnBr stretching frequencies decrease (173 → 120 cm −1 for ZnI, 196 → 157 cm −1 for ZnBr). The decrease of the ZnI and ZnBr band frequencies was attributed to the increase of the number n of the ZnX n Cl 4− n 2− tetrahedra. The increase of the ZnCl frequency suggests the existence of the bonding state of Cl − ions which is intermediate between the bridging and the non-bridging states. In ZnCl 2 KX glasses, the ZnCl non-bridging band at about 300 cm −1 was observed in addition to the bands observed in ZnCl 2 ZnX 2 glasses. The addition of KX produces non-bridging anions while the tetrahedral units, ZnX n Cl 4− n 2− are also formed.

Toughened glass-ceramics containing ZrO2 and Al2O3 prepared by the sol-gel process from metal alkoxides

Abstract Glasses of compositions 5ZrO 2 ·5SiO 2 (ZS), 5ZrO 2 ·Al 2 O 3 ·4SiO 2 (ZAS) and 5 5ZrO 2 ·0.5Al 2 O 3 ·0.5Na 2 O·4SiO 2 (ZANS) were prepared by the sol-gel process from metal alkoxides and sintered to make glass-ceramics. Tetragonal ZrO 2 was precipitated by heat treatment at 900 to 1300°C. The activation energy for tetragonal ZrO 2 crystal growth was extremely high in Al 2 O 3 containing glasses. ZAS and ZS were sintered to the near theoretical densities above 1200°C, at which the predominant phase was tetragonal ZrO 2 . On the other hand, for ZANS, high densification was not attained owing to the large pores enclosed by the glass phase. Strength and fracture toughness increased with the densification and the crystal growth of tetragonal ZrO 2 , reaching 450 MPa and 9 MN/m 1.5 , respectively.

Film formation of dititanium nitride by the dynamic mixing method

Abstract Coating film formation of titanium nitride is studied by means of the dynamic mixing method, where the deposition rate of titanium and the current density of nitrogen ions are widely changed and, for the first time, films of the pure Ti 2 N phase are prepared in a narrow range of the ratio of the deposition rate of the titanium and the current density of the nitrogen ions, Ti/N. Under the condition that the ratio Ti/N is larger than for Ti 2 N formation, a film consists of three phases: α-Ti, Ti 2 N and TiN. For lower Ti/N, the prepared films are a mixture of two phases: Ti 2 N and TiN. In the case of a much lower Ti/N only TiN films are prepared.

Optical non-linear property of Au colloid-doped glass and the laser irradiation stability

The optical non-linear property of an Au colloid-doped glass was measured by degenerate four-wave mixing (DFWM) experiments using a frequency-doubled Nd:YAG laser with 7 ns pulse duration. The pulse duration of the phase-conjugate reflection was 4 ns, indicating the fast response time of the glass. The third-order susceptibility χ(3) was estimated to be 2.5 × 10−11 e.s.u. (3.5 × 10−19 m2 V−2). The photodarkening effect was not observed and the phase-conjugate reflection was stable against the laser irradiation.

Novel halide glasses based on systems of LiX (X = Cl, Br, I)

Abstract New halide glasses have been obtained in systems of LiXKXCsXBaX2 (X = Cl, Br, I) where the main component is LiX. The glasses first discovered are those which contain only alkali halides and alkaline earth halides. Glass transition and crystallization temperatures were in the range of 40–80°C and 65–105°C, respectively. The IR cut-off wavelength is beyond 10 μm. These glasses have high ionic conductivity, e.g., for the LiI-based glass, 5.8 × 10−7 S/cm at 25°C.

Structural study of ion-conducting MX-K (or Rb) X-CsX-BaX2 halide glasses (M = Li, Cu or Ag) with single X species (X = Cl, Br or I)

Abstract The structures of MX-based glasses (M = Li, Cu or Ag; X = Cl, Br or I) which were developed quite recently were examined in comparable MX-KX-Cs(or Rb)X-BaX2 compositions with single X species using molecular dynamics simulation, an X-ray radial distribution analysis and an EXAFS analysis. Structural features such as the X− coordination environments around M+ and the linkage manners of MXn polyhedra were analyzed in detail and discussed based on the structural data of MX crystals. In almost all the glasses, the majority of MX exists as MX4 tetrahedra which are linked by the corner sharing, building up a three-dimensional random network.