Narrow-band spectral features of structured silver surface with rectangular resonant cavities

This paper is aimed to investigate spectral properties of structured silver surface with periodic rectangular hollow cavities. Numerical computation is conducted to obtain spectral distribution of surface absorptance with different structural parameters using the finite-difference time-domain (FDTD) method. By means of numerical examples, the effects of structural parameters, incident angle and azimuthal angle on the spectral features of the structured surface are discussed. It is found that the structured surface shows the characteristics of the peak absorption in the vicinity of resonant wavelength of rectangular cavity. For some special structure parameters, the peak absorptance of the incident plane wave can reach as high as above 80% due to the excitation of microcavity effect. The optimal narrow-band absorption can be achieved by the rational design of the structural parameters of rectangular cavity. The directional dependence of spectral absorptance is also analyzed and the results reveal that the absorption peak positions are incident-angle-independent. The results show that the microscaled rectangular cavities fabricated on the low-emissivity silver surface are very efficient for selective improvement of the radiative features, which provides guidance for the design of narrow-band infrared thermal emitters.

Research Highlights► The incident-angle-dependent variation of the absorptance of the structured surface. ► The absorption curves are symmetrical at the azimuthal angle of 45o. ► The structured surface exhibits high emission at the same wavelength in all directions.