All-polymer whispering gallery mode resonators for gas sensing

Sensitivity of polymeric microdisks is evaluated for selected compounds in their vapor phase such as humidity, isopropanol, toluene, limonene, 1-butanol, and pentanoic acid (valeric acid). Among these compounds, pentanoic acid exhibits the highest sensitivity (23 pm/ppm) with a limit of detection estimated to be around 0.6 ppm. We are interested in the contribution of the geometry deformation due to polymer swelling on the sensitivity as it may be engineered to improve performance of gas sensing devices. Experimental observations show a trend where sensitivity to humidity increased with the ratio of the undercut over the radius of the microcavity.