Nanoporous Glass Surface for Backscattered Waveguide Fluorescence Application

Nanoporous material-based sensors promise easier integration into portable devices. Here, we use a nanoporous layer (similar to 130 nm thick) fabricated on a cover glass as a planar waveguide and integrated sensing surface. A combination of custom-built planar waveguiding experiments and the Zemax ray tracing model confirmed that the nanoporous surface produced an increased in-plane waveguide signal output in backscattering mode. Also, by addition of a fluorophore (coumarin 6) on the surface, the nanoporous glass showed increased interactions between the dye and in plane waveguided light, resulting in 4-6x higher emission. Utilizing the nanoporous glass as an integrated chemical and mechanical surface, we report a fluorescent planar waveguide-based oxygen sensor that is operational in backscattering mode. We showed an 11x improvement in the sensing signal upon using an appropriate filter and a similar to 2X overall improvement for the nanoporous glass over plain glass in oxygen sensing. The Stern-Volmer (SV) plot confirmed an increase in the overall interactions between the dye, waveguided light, and the analyte gas for the observed improvements. Thus, having a inbuilt nanoporous layer on glass demonstrated improved performance for a surface integrated application.