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

In the present study, a dual-dielectric planar waveguides （PWGs） 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 EIT-like resonance. The sensitivity and quality factor （Q） of the device was 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, a biosensor designed in this work displayed high-resolution capability and good linearity, along with a limit of detection （LOD） down to 0.14 mg/dL for label-free glucose measurement. This suggests the vast potential for environmental protection, drinking water safety, and biomedical discoveries