Breaking performance limit for waveguide sensor: A way of both enhancing sensitivity and quality factor

In the present study, a dual-dielectric planar waveguide (PWG) coupling sensor was developed to break the waveguide performance limit. Its designs consisted of a sensor planar waveguide (PWG1) for the realization of multimode sensing and a reference planar waveguide (PWG2) for the realization of Fano and electromagnetically induced transparency (EIT)-like resonance. The sensitivity and quality (Q) factor of the device were shown to achieve values of up to 7.8 × 104 nm/RIU and 4843.75, respectively, allowing its applicability for bulk refractive index (RI) sensing. This yielded an impressive Figure of Merit (FOM) of 2.2 × 105 RIU−1, which was the highest reported FOM for an RI sensor. Furthermore, the reaction between the Streptomycin monoclonal antibody and Streptomycin-BSA measured in this work displayed high resolution capability and good linearity. This suggests the vast potential for environmental protection, drinking water safety, and biomedical discoveries. •The limitations of sensor performance were broken by both enhancing sensitivity and quality factor.•Multimode sensing of ultra-high sensitivity with planar waveguide has been experimentally realized for the first time.•High-quality peak can be clearly identified by the shape difference of EIT-like and Fano resonances.