Ultra-narrow dual-band perfect absorber based on double-slotted silicon nanodisk arrays

Abstract

Due to its unique advantage of optical properties, nanophotonic metamaterials have gained extensive applications in perfect absorbers. However, achieving both dual-band and ultra-narrow linewidth in absorbers simultaneously remains a challenge for typical metal-dielectric based metamaterials. In this work, a dual-band ultra-narrow perfect absorber consisting of a double slotted silicon nanodisk array that located on a silver film with a silica spacer layer is proposed theoretically. By combining the hybrid mode excited by the coupling of diffraction wave mode and magnetic dipole mode with the anapole–anapole interaction, two absorption peaks can be induced in the near-infrared regime, achieving nearly perfect absorbance of 99.31% and 99.61%, with ultra-narrow linewidths of 1.92 nm and 1.25 nm respectively. In addition, the dual-band absorption characteristics can be regulated by changing the structural parameters of the as-proposed metamaterials. The as-designed metamaterials can be employed as efficient two-channel refractive index sensors, with sensitivity and figure of merit (FOM) of 288 nm RIU−1 and 150 RIU−1 for the first band, and sensitivity and FOM of up to 204 nm RIU−1 and 163.2 RIU−1 for the second band. This work not only opens up a new design idea for the realization of dual-band perfect absorber synchronously with ultra-narrow linewidth, but also provides potential attractive candidates for developing dual-frequency channel sensors.