Temperature Self-Compensated Biosensor Based on No-Core-Fiber Offset Microcavity for Label-Free BSA Detection

A simple Mach-Zehnder interferometer (MZI) induced by no-core-fiber (NCF) offset microcavity is proposed and demonstrated for temperature self-compensated biosensing. The microcavity is fabricated by online fiber cutting-welding method. Benefiting from the directly interact between microfluidics and fiber core signal in microcavity instead of evanescent wave, an ultrahigh RI sensitivity of −12146 nm/RIU was obtained by experiment with a temperature cross-sensitivity of 2.05 nm/°C. The influence of microcavity length was analyzed in detail. Temperature self-compensation can be realized by solving a multivariate matrix. Finally, the bovine serum albumin (BSA) samples in different concentrations were detected to evaluate the biosensing capability. Experiments demonstrated that the designed sensor exhibited a BSA concentration sensitivity of −10.4 nm/mg/mL and a detection limit (DL) of
$1.9~\mu $
g/mL, which shows great potential for label-free biochemical trace detections without temperature-induced cross-sensitivity.