Broadband terahertz absorber design based on fractal structure

In this work, a second-order Minkowski fractal broadband absorber based on a conventional sandwich structure is proposed. The design was developed from the conventional square-ring microwave absorber. The improvement is divided into two major parts: the evolution of structural parameters as well as the evolution of patterns. The first part is realized based on the analysis of the model structure and the equivalent circuit, and the second part is realized by introducing the internal coupling of the pattern using a second-order Minkowski structure. This proposed absorber exhibits an absorption greater than 90% between 0.283 terahertz (THz) and 0.689 THz. The absorber is polarization-insensitive and possesses good incidence angle stability. In order to verify the performance of the absorber through experimental research, ultraviolet lithography technology is used to manufacture an absorber sample. A terahertz time-domain spectroscopy system is used to measure the sample, and the measurement results are consistent with the simulation results, verifying the correctness of the absorber design.