Research On Optical Waveguide Chemical Sensor System

Since 1990s, optical waveguide (OWG) used optical communication have attracted considerable attention. Use this technique can fabricate new type chemical sensor regarded to the light propagated in OWG is very sensitive to the change of OWG surface. In this dissertation some research work were done on planar OWG sensor system described below:1. Researched on the relationship between physical parameter (thickness, refractive index) and surface sensitivity of planar OWG, and improved the calculation method of sensitivity calculation model of thin film OWG sensing element and modeling an analyzing method of evanescent wave OWG sensing element sensitivity. Designed sensitivity calculation software using sensitivity calculation model and the software provided good result for designing highly sensitive sensing element. A reliable parameter achieved for calculation of OWG sensing element sensitivity by improvement the previous calculation method of refractive index of thin film.2. The research work were done on intelligentize of the OWG detecting system. The OWG detecting system linked to the computer by data sampling card, and the data sampling and on time drawing graphic soft ware was designed, and the detecting system capability enhanced by these work. This is the preparatory work for miniaturization of OWG sensor detecting system.3. Use Congo Red (CR) Cross-linked Poly(vinyl alcohol) (PVA) as a sensitive material, two type glass optical waveguide (OWG) acidic gas sensing element were fabricated by coating a thin film of CR-PVA on the surface of K⁺ ion-exchanged glass OWG and TiO₂ thin film / K⁺ ion-exchanged glass OWG with spin coating. The results show that the two type sensing element have rapid, reversible and good liner response for an HCl concentration of several 10^-9. The low concentration of SO₂,NO₂,H₂S gases and VOCs has no interference to detecting HCl gas. 4. Use Triethanolamine complex of copper as a sensitive material, studied the UV-vis spectra before and after pumped in SO₂, HCl, NO_x, H₂S, NH₃ gases to sensitive material ethanol solution, and a selective glass OWG SO₂ gas sensing element was fabricated. The results show that the sensing element can detect an SO₂ concentration of several 10^-9. The low concentration of HCl, NO₂, H₂S and NH₃ gases and VOCs has no interference to detecting SO₂ gas.