Impact of resonator rotational symmetry on infrared metamaterial absorber

The impact of rotational symmetry of the metamaterial perfect absorber on its performance was investigated. The absorber consists of a metal particle/dielectric-spacer/metal film structure. Using a square metal particle as an example structure and by introducing small air holes to the different y-direction sides of it, we study the absorption properties of the fourfold, twofold and non-rotational rotational symmetrical absorber. The calculated results show that when the polarization of the incident light parallels to x axis or y axis, the same single absorption peak appears in the absorption spectrum. The absorption peak of the twofold rotational symmetrical structure splits into two peaks when the polarization of the incident light parallels to x axis. The absorption peak splits into two peaks no matter the polarization of the incident light parallels to x axis or y axis in the case of non-rotational symmetry. The results of the absorption peak properties with different rotational symmetry may be helpful to design novel polarization-insensitive absorbers.