Bio/chemical sensors based on liquid core optical ring resonators

Optical ring resonators in the form of a microsphere or microcylinder of a few tens to a few hundreds of mu m in diameter represent a new sensing mechanism and have recently drawn increasing attention in bio/chemical sensor development. In a ring resonator, the light circulates along the inner surface in the form of the whispering gallery modes (WGMs) resulting from total internal reflection. Due to the high Q-factor of the WGM, the effective interaction length between the light and the analytes can be 10-100 cm long, despite the sensor's micrometer dimensions. Successful feasibility demonstrations of a single ring resonator sensor have stimulated further investigation on photonic and fluidic integration. In this paper, we present a novel bio/chemical sensor platform based on a liquid core optical ring resonator (LCORR) architecture that takes advantage of the high sensitivity associated with ring resonators and easy sample delivery associated with the hollow core colurrins. This structure allows for separate engineering of the fluidics and photonics and is well-suited for a 2-D sensor array. The potential result is a micro-sized sensing system capable of detecting multiple agents simultaneously while providing redundancy to reduce false positives. In addition, the sample detection volume can be as low as 100 pL. Here we present an LCORR with a Q-factor of 500,000 (2 pm mode linewidth) and a refractive index sensitivity of 7 nm/RIU. Also, we demonstrate the detection of bovine serum albumin adsorbing to the inner surface as the sample is pumped through the LCORR.