Porous silicon microcavities for optical hydrocarbon detection

Large, repeatable and selective red-shifts in the reflectivity spectra of porous silicon microcavities (PSMs) have been registered after exposure to vapour or dip into liquid aliphatic hydrocarbons with different molecular weights. The shift in the resonant peak of the optical microcavity is due to average refractive index changes, induced by capillary condensation of the organic species into the silicon pores.