Thin film waveguide sensors for chemical detection

Chemical sensor scheme based on selective sensing surfaces and highly sensitive integrated optical transduction is presented. Self-assembly techniques are used to covalently attach species selective films onto the surface of silicon nitride waveguides. Exposure to targeted analytes results in selective absorption of these molecules onto the waveguide surface causing a change in the effective refractive index of the guided modes. These relative changes in effective refractive indices of TM and TE modes are using Zeeman interferometry. The measurements demonstrate reversible, real-time sensing of volatile organic compounds at ppm level. Improvements in the waveguide design are proposed to further increase the sensor performance.