Characterizations of an infrared polarization-insensitive metamaterial perfect absorber and its potential in sensing applications

•The absorption behavior is explained and predicted by equivalent circuit model.•The absorption characteristics are examined by simulations and FTIR spectroscopy.•The absorption frequency is well predicted by the magnetic resonance theory.•The dielectric-thickness dependent absorptivity can only be explained by the destructive interference theory.•The sensing potential in the infrared region is numerically verified. An increasing interest has been paid for metamaterial perfect absorbers, which offer attractive platforms for electromagnetic radiation based sensing applications. In this paper, we systematically characterize an infrared polarization-insensitive metamaterial absorbers by means of finite integration simulations and spectroscopic experiments. The metamaterial absorber is composed of symmetric disk-type metal-dielectric-metal structure, which shows a near-unity absorption peak at about 70 THz. It is found that the absorption frequency can be well predicted using the magnetic resonance theory while the dielectric-thickness dependent absorptivity can only be explained by the destructive interference theory. Spectral analysis reveals the possibility of using the proposed absorber as a high-performance refractive-index and thickness sensor for novel sensitive IR inspection technologies.