| Research Abstract |
1) Applying optical waveguides to monitoring solid surfaces. We have many important reactions taking place at solid surfaces. Thin films on the solid surfaces are also increasing its importance in industry. In conjunction with these, we proposed a use of optical wave-guide (OWG) for sensitive detec tion on chemical reactions on the surfaced of the solids and/or the thin films (1988).
2) Development of OWG systems for surface monitoring, The following approaches were made in this project.
2.1) A use of adiabatic transition of light in OWGs. An OWG with a thick guiding layer, and hence with small attenuation, was covered with a thin film OWG having high surface sensitivity. The two OWGs were combined with taper velocity couplers. As a typical example, we made FePO_4 thin film OWG on a glass OWG. It was found that the taper velocity coupler needs to be 0.5 mm long for the 0th mode, and 1 mm for the 1st mode to realize totally adiabatic conditions. A band OWG was constructed by using this technique, and relative sensitivity (S) was measured for surface species. The S values were about 10^3, being several tens of times as large as that for glass OWGs.
2.2) New materials for OWG components. Thin films of peroxopolytungstic acids were made from their solutions and with spin-coating, and basic optical characteristics were examined to make OWG components. Their refractive indices were >2.0, being very high for thin films cured at 100^ﾟC. Thin film OWGs, ARROW type OWGs, and embossed grating were prepared from these thin films. Moreover, basic characteristics of glass OWGs were examined in detail to construct chemical sensors based on photochromism of WO_3.
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