High-sensitivity micro-nano sensor based on q-BIC effect for viral differentiation

A micro-nano optical sensor consisting of a rectangular waveguide integrated with a built-in baffle and a rectangular resonant cavity is proposed in this paper. Surface plasmon polaritons (SPPs) are excited by incident light, and surface plasmon resonance (SPR) is achieved via the SPPs stimulated by the rectangular coupling cavity and the baffle, thereby forming a quasi-bound state in the continuum (q-BIC) and further inducing Fano resonance. After structural parameter optimization, the sensor exhibits a full width at half maximum (FWHM) of 53 nm, a Q-factor of 21, and a sensitivity of 1133 nm/RIU. The sensor is further employed for sensing detection of cells infected with four types of viruses, namely Herpes Virus type-1, Influenza A, HIV-1, and M13 bacteriophage. Experimental results reveal that different viruses correspond to distinct resonant wavelengths in their resonance peak responses, which validates that the proposed sensor is capable of detecting cells infected with the above four viruses. This work offers a promising strategy for future developments in biomedical sensing.