The liquid core optical ring resonator (LCORR) sensor is a newly developed capillary-based ring resonator that
integrates microfluidics with photonic sensing technology. The circular cross-section of the capillary forms a ring
resonator that supports whispering gallery modes (WGM). The WGM evanescent field is exposed to the capillary core
and detects the aqueous samples conducted by the capillary using a label-free protocol. The high-Q of the WGM allows
for repetitive light-analyte interaction, resulting in excellent sensitivity. Recently a detection limit of the LCORR on the
order of 10-6 refractive index units was reported.
In this work, we have further integrated the LCORR with an anti-resonant reflective optical waveguide (ARROW) array
for multiplexed sensor development. The ARROW, with an array of 8 waveguides separated by 250 microns each,
consists of a core and a lower reflective double-layer with alternating high and low refractive index, and thus has a
significant evanescent field above the waveguide. The WGM is excited at each LCORR/ARROW junction
simultaneously when the LCORR is brought into contact with the ARROW array. We experimentally investigated the
optimal waveguide geometry for WGM excitation using a range of waveguide heights from 2 to 5 microns.
Furthermore, the LCORR/ARROW system is utilized for a biomolecule sensing demonstration.
The LCORR/ARROW system is not only essential for assembling a robust, practical, and densely multiplexed sensor
array, but also enables on-capillary flow analysis that has broad applications in capillary electrophoresis,
chromatography, and lab-on-a-chip development.