Grating Coupled Waveguide Biosensor Based on Porous Silicon

ABSTRACTPorous silicon waveguides with integrated porous silicon grating couplers are demonstrated as small molecule biosensors. Two fabrication methods are presented for the grating couplers: standard electron beam lithography with reactive ion etching and a new technique based on direct imprinting of porous substrates. Although the gratings fabricated using standard lithographic techniques have steeper sidewalls and enable a larger available sensing surface area inside the waveguide, the imprinted gratings have the advantage of rapid and low-cost fabrication. Both the lithographically and imprinted sensors are shown to have waveguide losses on the order of 10 dB/cm, and both are demonstrated for detection of 16mer nucleic acids.