- 2016 SPIE. A chip-scale biochemical sensor was developed using mid-Infrared (mid-IR) transparent silicon nitride (SiN) optical waveguides. The label free detection was conducted at = 2.70-2.81 m because these spectral regions overlap with the characteristic glucose absorption associated with O-H stretches. Strong intensity attenuation at > 2.73 m was found for the SiN waveguide covered by glucose and a detection limit less than 0.5 ng was experimentally demonstrated. The observed high sensitivity is attributed to a long mid-IR-glucose interaction length owning to the waveguide geometry and an increased sensing surface from the pedestal structure.