Sensitive Monitoring of Surface Reactions with Optical Waveguide Dynamic Spectroscopy

1)应用光波导监测固体表面。我们有许多重要的反应发生在固体表面。固体表面上的薄膜在工业上也越来越重要。与此同时，我们提出了利用光波导（OWG）对固体和/或薄膜表面上的化学反应进行灵敏检测（1988）。2）发展用于表面监测的OWG系统。一个OWG与厚的引导层，因此具有小的衰减，覆盖有薄膜OWG具有高的表面灵敏度。这两个OWG与锥形速度耦合器相结合。作为一个典型的例子，我们在玻璃OWG上制备了FePO_4薄膜OWG。发现锥形速度耦合器对于第0模需要0.5 mm长，对于第1模需要1 mm长，才能实现完全绝热条件。利用该技术构建了一条带OWG，并测量了表面物种的相对灵敏度（S）。S值约为10^3，是玻璃OWG的几十倍。2.2）OWG组件的新材料。用旋涂法制备了过氧多钨酸薄膜，并对其基本光学特性进行了测试，以制备OWG组件。它们的折射率>2.0，对于在100 ° C下固化的薄膜是非常高的。用这些薄膜制备了薄膜OWG、ARROW型OWG和浮雕光栅。此外，我们还对玻璃光波导的基本特性进行了详细的研究，以构建基于WO_3光致变色的化学传感器。

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.