Novel porous silicon vapor sensor based on polarization interferometry

Optical form birefringence property of porous silicon is used in a compact polarization interferometer to demonstrate a novel optical transduction mechanism for vapor or gas sensing applications. This technique uses high interferometric sensitivity of polarization interference intensity when the porous silicon sample is exposed to solvent vapors. We experimentally demonstrate that the relative variation in the polarization interference intensity at a fixed incidence angle provides means to quantify the detected concentration of solvent vapors. Examples of detecting heptane and ethanol vapors indicate good potential of the novel transduction mechanism for other chemical and biological sensing applications.