Realizing near-perfect absorption at visible frequencies.

Sub-wavelength hole array (SHA) combined with thick metal layer (TML) is shown to have simultaneous suppressed transmission and reflection, resulting near-perfect absorption. Unlike the simultaneous electric and magnetic resonances in electric ring resonator and cut wire [PRL, 100, 207402 (2008)], such behavior results from strong anti-symmetric surface plasmons coupling supported by SHA and TML. The polarization-free characteristic permits to construct an ideal absorber for some practical applications in turbid backgrounds.