A composite optical waveguide NO2 sensor based on an amino group containing siloxane

作者：Xu YT; Yamada N; Hamada T; Amemiya T; Itoh K^*

来源：Electrochemistry, 2004, 72(5): 317-321.

• optical waveguide
• interferometer
• siloxane thin film
• nitrogen dioxide sensor

A composite-type optical waveguide was applied to a gas sensor using a thin film of siloxane polymer which absorbs NO2 gas. The waveguide was prepared by using ion exchange (K+-doped base layer, about 2 mum thick) and sputtering (TiO2 top layer, about 20 nm thick, with slopes on both sides). A highly sensitive interferometer was constructed on the basis of the difference in cutoff thickness for TE and TM modes. Changes in thickness or refractive index taking place in the polymer film coated on to the TiO2 part induce phase shifts (Deltaphi) of the propagating lightwave. NO2 gas with concentration less than 1 ppb was detected by measuring changes in Deltaphi as a function of time. The response was reversible for low concentration, and irreversible for high concentration. The irreversible changes were attributed to the ion-pair formation in the film.

• 出版日期2004-5