Polarization-Independent Absorber Based on a Cascaded Metal-Dielectric Grating Structure

The spectrum selective absorption effect of a vertically cascaded metal-dielectric grating structure is studied. A polarization-independent spectrum selective absorber based on two pairs of stacked metal-dielectric grating structures is presented for the infrared frequencies. The near-unity absorption with polarization independence is observed under normal incidence. The understanding of such a perfect selective absorption mechanism is illustrated by investigating the electric field distributions and power loss density at the resonant wavelength. The angle independence is also studied for this absorber and it is found that the absorber can maintain high absorbance around large incident angle range (0 degrees-33 degrees), especially for the TM polarization.