Thin film multi-layered chalcogenide glass waveguide structures have been fabricated for evanescent wave sensing of bio toxins and other applications. Thin films of Ge containing chalcogenides have been deposited onto Si substrates, with a-GeSe2 as the cladding layer and a-GeSbSe as the core layer to form the slab waveguide. Channel waveguides have been written in the slab waveguides by appropriate light the through a mask. The photo-induced structural changes in the core layer selectively enhance refractive index at the portions of interest and thus confining the light to the channels. The waveguides have been characterized and tested for the guiding of light.
The purpose of this study is to produce a platform device with the ability to detect a variety of pathogens based upon antigen-antibody interactions. The sensor comprises a nanoporous GeSe channel waveguide fabricated on a substrate, with an intermediate cladding buffer layer [GeSe2], which is required when the substrate does not transmit at the desired λ. The light from a laser source is then coupled through a fiber and prism into the waveguide and collected with the help of a lens into a detector. The top cladding layer is a Ge28Sb12Se60 thin film in which biomolecules can be 'tethered' via functionalization of the surface. Therefore the surface chemistry of the thin film and the specificity of antibody to its antigen are important considerations. This paper will focus primarily on the surface characterization of the top cladding layer using XPS, AFM, ellipsometry, contact angle measurements and diffuse reflectance analysis.