LAUSR

A biological sensing structure with a high-order mode ( E21y ) is designed, which is composed of a suspended racetrack micro-resonator (SRTMR) and a microfluidic channel. The mode characteristics, coupling properties, and sensing performances are simulated by using the finite element method (FEM). To analyze the mode confinement property, the confinement factors in the core and cladding of the suspended waveguide for the E11x , E11y , and E21y are calculated. The simulation results show that the refractive index (RI) sensitivity of the proposed sensing structure can be improved by using the high-order mode ( E21y ). The RI sensitivity for the E21y mode is ∼ 201 nm/RIU, which is twice to thrice higher than those for the E11x mode and the E11y mode. Considering a commercial spectrometer, the proposed sensing structure based on the SRTMR achieves a limit of detection (LOD) of ∼ 4.7 × 10−6 RIU. Combined with the microfluidic channel, the SRTMR can possess wide applications in the clinical diagnostic assays and biochemical detections.