Sensitivity to alcohols of a planar waveguide ring resonator fabricated by a sol–gel method

A planar waveguide ring resonator was fabricated by organic–inorganic hybrid sol–gel materials; its sensitivity to ethanol vapor was experimentally investigated. It was found that dips in the transmission spectrum of the device shifted to longer wavelengths with increasing the ethanol concentration, and its sensitivity showed a linear relation with the ethanol concentration, showing a coefficient of 1.13 pm/ppm. In addition, the transmission loss of the ring resonator decreased with increasing the ethanol concentration. The measured characteristics suggest that the device may be considered as one of the candidates of alcohol vapor sensors.