An ultra-narrow multi-band perfect absorber based on single dielectric nano-cylinder array with surface lattice resonance
Dielectric nanomaterials have attracted significant attention in the realm of micro- nano optics owing to the simultaneous low ohmic loss and distinctive electromagnetic resonance characteristic. However, achieving both ultra-narrow multi-band band and perfect absorption effects simultaneously has been challenging due to the weak magnetic response within traditional dielectric metamaterials. In this work, employing the finite-time domain differential method for simulation calculations, a multi-band perfect absorber consisting of titanium dioxide cylinder arrays is theoretically proposed. Benefiting from the concurrent presence of electromagnetic lattice resonance within the arrays of titanium dioxide cylinders, the as-proposed optical absorber demonstrates the simultaneous achievement of triple absorption bands, with extremely narrow spectral characteristics (minimum bandwidth approximately 0.8 nm) and near-perfect absorption rates (around 95.6%, 96.8%, and 95%) in 700–900 nm. Further near-field analysis unveils that surface lattice resonance arises from the synergistic interaction between the incident light and periodic structures, enhancing the coupling efficiency between the light and the surface plasmon, which can significantly amplify the electromagnetic field. By adjusting the lattice constant and geometric parameters, the physical mechanisms of the structure are further elucidated, and the optimal parameters of the absorber are ultimately determined. Moreover, due to its exceptional optical properties, the as-proposed multi-band absorber can be employed as a high-efficiency refractive index sensor with multi-frequency channel sensing. The corresponding sensitivity is calculated to be 356, 443.6 and 305.9 nm/RIU, with corresponding figure of merits of 482, 460.4 and 19.5 RIU−1, respectively. This research establishes a robust foundation for advancing multi-band perfect optical absorber, offering significant potential applications in multiple fields such as biochemical sensing, surface enhancement spectroscopy, and nonlinear nano-optics.
