Enhanced PNA Detection Sensitivity based on Polymer-cladded Porous Silicon Waveguide

In this work, we theoretically and experimentally demonstrate a highly sensitive polymer-cladded porous silicon (PSi) membrane waveguide based on a ~1.55 m thick porous silicon membrane coated on one side with a low loss polymer. The sensor operates in the Kretschmann configuration, which is amenable to microfluidics integration, with a high index cubic zirconium prism. The sensitivity of the sensor is investigated through PNA hybridization in the PSi membrane. We demonstrate that higher angle resonances and a proper ratio of PNA length to PSi pore diameter lead to significantly improved detection sensitivity. A detection sensitivity below 0.1/M is reported for 16mer target PNA. Calculations and complimentary experiments show that careful tuning of the polymer cladding thickness can further improve the detection performance.