title: Rapid chemical-vapor sensing using optofluidic ring resonators.
abstract: We develop rapid chemical-vapor sensors based on optofluidic ring resonators (OFRRs). The OFRR is a glass capillary whose circular wall supports the circulating waveguide modes (WGMs). The OFRR inner surface is coated with a vapor-sensitive polymer. The analyte and polymer interaction causes the polymer refractive index to change, which is detected as a WGM spectral shift. Owing to the excellent fluidics, the OFRR exhibits subsecond detection and recovery time with a flow rate of only 1 mL/min, a few orders of magnitude lower than that in the existing optical vapor sensors. The detection limit is estimated to be 5.6 x 10(-6) refractive index units, over ten times better than other ring-resonator vapor sensors. Ethanol and hexane vapors are used as a model system, and chemical differentiation is demonstrated with different polymer coatings.
authors.affiliation: Department of Biological Engineering, 240D Bond Life Sciences Center, 1201 E. Rollins Street, University of Missouri, Columbia, Missouri 65211, USA.
authors.forename: Yuze
authors.initials: Y
authors.lastname: Sun
authors.forename: Siyka I
authors.initials: SI
authors.lastname: Shopova
authors.forename: Greg
authors.initials: G
authors.lastname: Frye-Mason
authors.forename: Xudong
authors.initials: X
authors.lastname: Fan