We have demonstrated a novel sensor architecture based on a liquid-core optical ring-resonator (LCORR) in which a fused silica capillary is utilized to carry the aqueous sample and to act as the ring resonator. The wall thickness of the LCORR is controlled to a few micrometers to expose the whispering gallery mode to the aqueous core. Optical characterization with a water-ethanol mixture shows that the spectral sensitivity of the LCORR sensor is approximately 2.6 nm per refractive index unit. A model based on Mie theory is established to explain the experimental results. The LCORR takes advantage of the high sensitivity, small footprint, and low sample consumption with the ring resonator, as well as the efficient fluidic sample delivery with the capillary, and will open an avenue to future multiplexed sensor array development.
The authors demonstrate integrated biosensors utilizing antiresonant reflecting optical waveguides (ARROWs) to excite the whispering gallery modes of a liquid core optical ring resonator (LCORR) sensor. Because this architecture is based on integration, it is robust and well suited for dense multiplexing of sensors. They analytically and experimentally characterize the coupling between the ARROW structure and the LCORR and show good agreement between the coupling theory and experimental results. The multiplexing capability is experimentally demonstrated by exciting multiple ring resonators along a single LCORR using the ARROW array. Also, they show the label-free detection of bovine serum albumin with this LCORR-ARROW system.
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