▎ 摘　　要

A tunable polarization-independent coherent perfect absorber (CPA) is proposed based on the metal-graphene hollowed-out cross array nanostructure at the mid-infrared region. By adjusting the phase difference between the incident beams, the coherent absorption at 9969nm is all-optically modulated from 99.97% to nearly 0 with the modulation depth over 80dB. The absorption resonance of the CPA is tuned by the gate-controlled Fermi energy with the coherent absorption remaining nearly 100%. The CPA is also found to be angular insensitive to incident beams within the range of -12 degrees to 12 degrees. The central-symmetry nanostructure leads to polarization independence and the introduced graphene layer results in the electrical tunability of the CPA at the absorption resonance, which have prospects applications such as for tunable mid-infrared detectors, transducers, modulators, and optical switches. (C) 2017 Optical Society of America under the terms of the OSA Open Access Publishing Agreement