ポリタングステン酸薄膜を用いた新しい複合光導波路の作製

抄録

A new composite optical waveguide was fabricated using polytungstic acid (PTA). Thin films were prepared by spin coating of aqueous peroxopolytungstic acid (PPTA) solution on potassium ion exchanged glass optical waveguides (OWGs). Polytungstic acid (PTA), which was produced when the films were hardened by drying between 100∼180°C, gave a high refractive index of 1.9∼2.0. A PTA/K⁺ composite OWG structure (5∼8 mm wide) having tapers at both ends (1∼3 mm in length), was prepared by etching the PTA film in water (pH = 8.0∼8.5). These tapered structures work as optical couplers which efficiently transfer guided light from the potassium ion exchanged layer to the PTA thin film layer. The new PTA/K⁺ OWGs gave a very high optical sensitivity (e.g., 4.4 × 10³ times/cm as compared with the normal incidence of monitoring light) for adsorbed dyes and a low loss value (2.5 dB/cm) at the optimum PTA film thickness of 65-70 nm. Such a PTA/K⁺ composite optical waveguide (OWG) could be applied to biochemical sensors and to the monitoring of surface chemical reactions with high sensitivity.