Broadband polarization-insensitive absorbers in 0.3-2.5 mu m using helical metamaterials

We present two kinds of broadband and polarization-insensitive metamaterial (MM) absorbers operating in about 0.3-2.5 mu m, including a racemic type and a reflected type. Through finite-difference time-domain simulation, we find that both designs are broadband in function and insensitive to polarization. In comparison, we find that the reflected type absorber possesses broader bandwidth (0.36-2.5 mu m) and exhibits higher average absorbance (88.9%), while the racemic type is superior in its polarization-insensitivity characteristic. Differing from designs of most planar MM absorbers based on perfect impedance matching, our designs are based on the principle of mutual radiation. (c) 2013 Optical Society of America