Mid-infrared waveguide evanescent field chemical sensor for liquids

Based on a midinfrared waveguide fabricated from germanium on silicon substrates, concept of chemical sensors in aqueous solutions is presented. The sensing scheme is utilizing the evanescent wave in a single-mode waveguide, and the absorption spectrum of chemicals dissolved in liquids. The waveguide is coupled to a single mode midinfrared quantum cascade laser, and an infrared detector. The wavelength of 5.81 microns is chosen to assure the specifity and sensitivity of the pilot application for the analysis of cocaine analyte, in a water based matrix (saliva).