Yanbing Ma, Huaiwu Zhang, Yuanxun Li, and Yicheng Wang
We report on the design, characteristics, and measurements of a terahertz (THz) metamaterial absorber (MA) based on fractal Sierpinski curves. By applying the fractal structure as the top resonators array, a more compact unit cell with a size reduction of 42% and dual-frequency operation has been achieved as an advantage over the conventional square-shaped MA. In addition, due to the rotationally symmetric structure, the fractal absorber is polarization insensitive and can perform well at a wide range of incident angles. Both the effective medium theory and the multireflection interference theory have been employed to investigate the underlying physical mechanism of the proposed THz MA, and it is found that the latter theory is not applicable for explaining the absorption mechanism of our investigated structure. The THz MA was measured in the case of 30° oblique incidence under TE polarization, and two absorption peaks have been observed at 0.2 and 0.58 THz with absorptivities of 91% and 92.2%, respectively. A microwave MA based on the same Sierpinski structure has also been demonstrated to validate the performance of the fractal MA at various incident angles, and good agreements between the full-wave simulation and experimental results have been achieved.
© 2014 Optical Society of America
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