All-metal frequency-selective absorber/emitter for laser stealth and infrared stealth

In this paper, an all-metal nanostructure is designed with a large frequency ratio (∼6) and a large bandwidth ratio (∼32), and consists of period slit-box cavities and nanodisk clusters. It is a nearly perfect absorber at 1.064 μm to achieve laser stealth, a frequency-selective emitter with low emissivity in wavelength ranges 3-5 and 8-14 μm to achieve infrared stealth, and also an emitter with near unity emissivity at 2.709 μm and 6.107 μm to compensate for the decrease of radiation heat transfer owing to the low emissivity. The absorption/emission peaks are all the Lorentzian shape, and the bandwidths, defined as full width at half-maximum, are 35, 408, and 1124 nm at 1.064, 2.709, and 6.107 μm, respectively. The electric and magnetic field distribution shows that the slit behaves like a capacitor, the box behaves like an inductance, and the nanodisk clusters can excite electric dipole resonance. Considering the solar irradiation, the nanostructure maintains middle-wavelength infrared signal reduction rates greater than 80% from 450 to 1000 K, and long-wavelength infrared signal reduction rates greater than 90% from room temperature to 1000 K. The laser and infrared stealth performances of our nanostructure at 473 K are also studied with different incident angles and polarization angles.