Narrow-band perfect absorption utilizing higher-order surface plasmon resonance

Metamaterial perfect absorber is a typical functional electromagnetic material and holds great potential in application fields such as highly efficient ulitization of solar energy. Up to date, most works are dovoted to the tunability of working wavelength as well as realization of dual-, triple- and even broad-band perfect absorption. However, applications such as laser protection require that the metamaterial peferct absorber can function at specific wavelength with narrow bandwidth, and work devoted to this direction is rather rare. In this work, based on a triple-layer structure made of Al back mirror–SiO₂ spacer–Al disk, a narrow-band metamaterial perfect absorber working at 1 064 nm was proposed and studied by numerical simulations. It was found that, compared to utilizing the fundamental mode of plasmonic resonance of smaller structure unit, utilization of higher-order mode of larger structure unit allowed for a narrower bandwidth of perfect absorption at designated wavelength. In addition, through systematic study of the geometric parameters such as the thickness of spacer layer, the diameter of the Al disk and the period of the lattice, the influence of such geometric paremeters on the optical response of metamaterial perfect absorber was revealed. Based on these findings and through optimization of geometric parameters, a high performance and narrow-band metamaterial perfect absorber design was obtained with a zero transmittance, a reflectance as low as 8.56×10⁻⁵ and a bandwidth of about 55 nm. Since all the materials involved are CMOS compatible, and the characteristic dimensions of the structure unit lie within the range of feasible fabrication method such as optical lithography, the metamateiral perfect absorber proposed here holds good promise towards large-scale real-world applications.