High Sensitivity Sensor Based on Porous Silicon Waveguide

Porous silicon (PSi) waveguides are fabricated as a new platform for high sensitivity biosensors. Biomolecules infiltrated into the PSi waveguide increase the effective refractive index of the waveguide and change the angle at which incident light couples into a waveguide mode. Due to the high surface area to volume ratio of PSi and the confinement of optical energy in the region where the biomolecules reside, the waveguide resonance is very sensitive to small concentrations of infiltrated molecular species. A resonance width below 0.1 ̊ has been obtained, which is sufficient to detect one monolayer of DNA covering the pore walls. In this work, a prism is used for the waveguide coupling in an arrangement that is similar to traditional surface plasmon resonance (SPR) sensing. Theoretical analysis suggests that an optimized PSi waveguide resonant sensor will show a 60-fold improvement in sensitivity when compared to a conventional SPR sensor due to the enhanced interaction between the electromagnetic field and biological material.