High Sensitive Gas Sensor Application Based on a Small Defect in Silicon Waveguide

A small defect in silicon nanowire waveguides is applied for gas sensors. Small defects with some special shapes and indexes can produce strong resonances with the incident light and induce large loss. Since the silicon waveguide has air cladding, the position of resonant peaks will be sensitive for the variation of the ambient air composition. The sensor based on the principle has a high sensitivity. As an example, we monitored the change of the position of the resonance peak as a function of alcohol concentrations in air. Results showed that a ~5-mg/L ethanol vapor in the air can result in a ~20-nm wavelength shift of the resonance.