Tunable perfect absorber from visible to near-infrared with insensitive properties to incident angle and polarization

In this paper, we propose an Insulator-Metal-Insulator-Metal (IMIM) nano-block array structure, which can achieve tunable single-peak and double-peak perfect absorption properties from visible light to near-infrared. Compared with our previous work, this paper additionally points out that due to the coupling effect between SPPs, the original bule-shifted spectrum is converted into red-shifted during the process of changing the thickness ratio of the middle silver nano-block to the SiO2 nano-block. In the design parameter range, two different structural parameters can be found, which the absorption peak is exactly the same, and the short-wave absorption peak position has the characteristics of "on" and "off". Based on the nature of absorption spectrum, it can be applied to optical switches in optical circuits. And this work also provides a new idea for plasma sensors, which has broad application prospects in the fields of filtering and imaging.