Multiband absorber and design method thereof

The invention relates to a multi-band absorber and a design method thereof. The multiband absorber can be used for absorbing light and comprises a reflecting layer, a substrate, a waveguide layer and a micro-nano unit array which are stacked in sequence, the micro-nano unit array comprises a plurality of micro-nano units, the micro-nano unit array has a row direction and a column direction, and the row direction and the column direction intersect with each other and are respectively parallel to the waveguide layer; each row of micro-nano units arranged in the row direction in the micro-nano unit array has a first array period, each column of micro-nano units arranged in the column direction in the micro-nano unit array has a second array period, and the first array period is smaller than the second array period. According to the multi-band absorber, the strong coupling condition of local surface plasmon resonance and a waveguide mode can be achieved, and the high absorption rate is achieved by reducing the re