Ultrasensitive Metasurface Biosensors by the Use of Constrained Mie Resonance and Metallic Dissipation

The figure of merit FOM
^*
is a vital evaluating indicator for optical biosensors' performance. This paper presents a metasurface in the visible regime, which has an extremely high FOM
^*
up to 304400/RIU higher than the values in many previous reports. In the broad range of the refractive index from 1.30 to 1.49, the refractive index's detection accuracy can reach 0.0001 RIU. For the adsorbed analyte's sensitivity, the biosensor achieves a high FOM
_layer
up to 91.1/nm and demonstrates excellent feasibility for the trace-amount analysis in biosensing. The high biosensing performance for an adsorbed layer with a thickness of 1 nm can show the potential in molecular layer detection. Its high biosensing performance originates from the excitation of Mie resonance in the dielectric part that can constrain the incident energy into the metal counterpart. In the previous researches, Mie resonances are generally excited in high-refractive-index dielectric nanoresonators. In this work, we find that the low-refractive-index dielectric nanoresonator can excite the Mie resonance under the existence of metal. The proposed metasurface provides a promising way to guide the design of ultrasensitive biosensors.