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Evanescent-field-coupled (EFC) waveguide-mode sensors can be used to detect nucleic acids or proteins from the changes in the local index of refraction upon adsorption of the target molecule on a waveguide surface. We recently described an EFC waveguide-mode sensor in which nanometric holes on a waveguide fill resulted in an improved sensitivity in the analysis of the interactions of biomolecules. In the present study, we have shown that sensitivity depends upon the diameter of the holes, where increase in diameter of holes increases spectral shift resulting in an improved sensitivity. Using this improved EFC waveguide-mode sensor, we could detect interactions between RNA and a small ligand, cyanocobalamin (vitamin [B.sub.12]), and between RNA and a protein (human coagulation factor IXa). These two interactions were monitored on surfaces modified with biotin-streptavidin-biotin and N-(2-trifluoroethanesulfonatoethyl)-N-(methyl)triethoxysilylpropyl-3-amine, respectively.

A new type of photocatalyst is described that has used the enhanced electric field amplitude on the surface of Ag nanoparticles (NPs) in the spectral vicinity of their plasmon resonances, particularly for the near-ultraviolet region. The enhancement of the photocatalytic activity has increased with a decreased thickness of the Si[O.sub.2] cell.

The changes in the composition and optical properties of Ag[O.sub.x] thin films induced by thermal annealing are studied. Results reveal that the Ag aggregation region work as precursors to Ag nanoparticles upon visible laser irradiation.

Research describing the properties of the insulating material hydrogenated amorphous silicon oxynitride is presented. In particular the mechanism of electroluminescence is investigated.

Research describing the densification mechanism of ion-implanted silica glass is presented. In particular the increase in refractive index is investigated with reference to the fabrication of optical fibre gratings.

The effects of thermal annealing on the optical and structural properties of Ge-doped SiO2 thin films have been studied. The films have been prepared through chemical vapor deposition (CVD) and flame hydrolysis deposition. Results indicate that thin films formed through CVD have inhomogeneous Ge distribution with Ge oxygen-deficient centers. However, the Ge distribution became uniform when the films were annealed at temperatures higher than 800 C. There was also a reduction in the number of oxygen-deficient centers when annealing was done in an O2 atmosphere.

A blanket tungsten layer direct deposition method on SiO2 was developed by utilizing helium plasma preexposure. After an hour of exposure of helium plasma, Si-Si bonds were formed on the surface of SiO2. Also, the relationship between the thickness of the SiO2 and the etching time in a HF solution of 0.063% was shown. It was recommended that a proper plasma-exposure time must be identified due to the observed peeling off of the tungsten layer at its interface with the Si substrate.

We have developed a fluorescence enhancement system for biomolecular detection using a monolithic waveguide sensing plate. The plate consists of a thermally grown amorphous SiO2 layer, a Si single-crystal layer, and bulk amorphous SiO2. Waveguide-mode excitation in this plate produces an enhanced electric field on the plate surface, and therefore, signals from analyte-labeling fluorescent dyes are enhanced. In the present paper, we elucidate the impact of the system from viewpoints of the electric field enhancement factor calculated numerically and the analysis of the limit of detection estimated from experimental results. Optimal layer thicknesses of the plates to achieve the highest sensitivity are also discussed. Further, an interesting phenomenon that accompanied the waveguide-mode excitation, namely, photoluminescence from the amorphous SiO2 layer itself, is also reported. [ABSTRACT FROM AUTHOR]

Visible laser irradiation of AgOx thin films forms Ag nanoparticles, which then results in surface-enhanced Raman scattering (SERS). The efficiency of this Ag nanoparticle formation strongly depends on the properties of the AgOx thin films. Thermal annealing causes changes in physical properties such as deoxidization of the films and aggregation of Ag atoms in the films. In the present research, the effects of the changes induced by thermal annealing on SERS efficiency were examined. It was found that AgOx thin films annealed at 300 °C for 5 min in a N2 atmosphere were suitable for the formation of Ag nanoparticles effective for SERS, while films that were not annealed were not. From these results, it was deduced that the Ag aggregation resulting from thermal annealing in AgOx thin films promotes the Ag nanoparticle formation. [ABSTRACT FROM AUTHOR]