Xiao-Min CHEN, De-Kui QING, Kiminori ITOH and Masayuki MURABAYASHI

Institute of Environmental Science and Technology, Yokohama National University, 156, Tokiwadai, Hodogaya-ku, Yokohama, 240 Japan

(Received May 2, 1996; Accepted June 11, 1996)

A composite optical waveguide for biological and chemical sensors was successfully developed by sputtering a thin TiO₂ film onto the surface of a low loss potassium ion-exchanged optical waveguide. The electric field of the evanescent wave at the film surface was made strong through adiabatic transition of the guided light. The attenuation of the guided light was sufficiently small in the air, and the guided light intensity was changed sensitively with the refractive index of the cladding layer (n_c). Thus, n_c can be sensitively monitored with a detecting sensitivity of about 10^-4.

Key words : optical waveguide, TiO₂ film, potassium ion-exchange, composite, relative sensitivity, refractive index sensor