Porous silicon waveguide biosensors with a grating coupler

Abstract

Sensitive label-free optical biosensors based on grating-coupled porous silicon (PSi) waveguides are demonstrated for biosensing applications. This is the first time that the benefits of both PSi and diffraction gratings have been combined for the detection of small molecules. The large surface area and strong field confinement in the waveguide region where biomolecules are immobilized make it possible to detect biomolecule interactions with high sensitivity. Diffraction gratings provide a simple, convenient, and effective means of coupling light into the waveguide for DNA hybridization experiments. Through both experiments and theoretical calculations, it was shown that an all-PSi grating-coupled waveguide biosensor exhibits a more than 30-fold larger signal response for small molecule detection compared to planar waveguide sensors. Kinetics parameters of different sized molecules in nanoscale pores were also determined for the first time using PDMS flow cell integrated PSi grating-coupled waveguides.