Sensitive slab optical waveguides composed of mesoporous metal-oxide thin films on the tin-diffused layers of float glass substrates

The application of uniform transparent mesoporous thin films for waveguide-based optical chemical and biological sensors could result in ultrahigh sensitivity due to a great increase in the depth of interaction between evanescent wave and analyte molecules adsorbed within the mesoporous film. For this purpose, we designed a low-loss, prism-coupling-compatible slab optical waveguide that can be prepared by deposition of sol-gel surfactant templated mesoporous metal-oxide thin films on the tin-diffused glass layers being intrinsic to float glass slides. In this study, mesoporous W O3 and Sn O2 thin films were fabricated and the resulting elements were demonstrated to keep the waveguiding capability and to allow for in situ detection of molecular adsorption within the mesoporous film by single-beam polarimetric interferometry. Induced changes in the phase difference between the fundamental transverse electric and magnetic modes were detected by two methods: (a) monitoring of an interference fringe on the waveguide surface and (b) detection of the light emitting from the prism coupler.