Self-referencing optofluidic ring resonator sensor for highly sensitive biomolecular detection.

The noise-suppression techniques of label-free optical ring resonator sensors are crucial to improve their practical sensing capabilities for biochemical analysis and detection in extremely small detection concentration. We have developed a self-referencing optofluidic ring resonator (SR-OFRR) to vastly improve its sensing capability as a label-free optical biosensor. By monitoring the mode-splitting separation generated on a coupled ring resonator system, the common-mode noise is suppressed by 2 orders of magnitude without any external noise-suppression techniques. In this work, we first carried out theoretical analysis to elucidate the sensing principle and then applied the SR-OFRR biosensor to experimentally detect bovine serum albumin with a concentration detection limit on the order of 1 pg/mL (~15 fM).