Fano resonance in a microcylinder-taper coupling system for liquid refractive index sensing via axial separation method

We propose and realize an axial separation detection scheme to measure liquid refractive index by utilizing a microcylinder-taper coupling system. Profiting from the clean resonance dip and distinctive light field distribution, a high sensitivity of 1029.6pm/RIU for detecting the liquid refractive index is achieved. As a good candidate for generating Fano resonance, asymmetric Fano linearity amplifies the detection sensitivity by 8.9 times compared to Lorentz dip by evaluating the small variation in the interaction area between the analyte and the mode field. This axial separation detection method can avoid the interference of the target analyte on the coupling region, making it attractive in practical sensing applications, especially in unstable biochemistry environments.