Multiband and broadband polarization-insensitive perfect absorber devices based on a tunable and thin double split-ring metamaterial.

We demonstrate a polarization-insensitive perfect absorber with multiband and broadband absorption based on a tunable and thin metamaterial, which consists of a double split-ring microstructure (DSRM) on double-layer and a coating substrate. The multiband absorption at different frequencies and broadband absorption with the relative bandwidth of 90.63% from 5.69GHz to 15.12GHz, of which the absorptivity is larger than 90%, can be achieved by changing the rotary angle of the proposed DSRM perfect metamaterial absorber (DSRM-PMA). The advantages of polarized-insensitivity, wide bandwidth and multiband absorption are illuminated by the angular absorptions and the surface current distributions. The DSRM-PMA device with similar geometry in simulation is fabricated and tested to clearly validate the functionality of our design. The simulated and experimental results indicate that the DSRM-PMA performs multiband and broadband absorptions with the rotary angle of 0° and 90° respectively.