Terahertz (THz) absorbers have drawn great attention due to their potential applications in high-resolution imaging systems, sensing, and imaging. In particular, metasurface-based THz absorbers have exhibited the exotic advantage in high efficiency and broad bandwidth benefitted from the excellent abilities of metasurface in flexible modulating electromagnetic (EM) waves. However, the interactions between metasurface and EM waves are complex, and the metasurface-based absorbers have many structural parameters to optimize for high performance. Therefore, the absorbers are constrained by the manual design process with limited geometry complexity and tedious parameters sweeping. In this paper, the genetic algorithm (GA) is employed to the design of THz metasurface absorber. The EM responses of metasurface device is calculated by a simple yet powerful analytic method derived from catenary field. The employment of GA can achieve the automatic design process and demand-oriented reverse design for high performance and decreasing time consumption. As a proof-of-concept, the broadband and monolayer metasurface terahertz absorber with absorbance exceeding 80% in the frequency range from 1 to 4 THz is designed by the proposed strategy based on five typical types of metasurface. The investigations of this article present important guidance and a promising approach to design and optimize metasurface-based devices for their practical applications.
The non-ionizing radiation and the high sensitivity to weak interactions of terahertz (THz) waves make THz technology a great applicability in the field of biosensing and medical detection. Besides, benefitted from the flexible capability of metasurface in manipulating the electromagnetic (EM) waves, the high-sensitivity THz sensors can be achieved to promote the development of THz sensing. However, the polarization dependence of hybrid-resonances-based metasurface and the single resonance cause the reduction in sensitivity, which is urgent to be settled. In this paper, we proposed a centrosymmetric metasurface to produce high-quality and polarization-insensitive resonance for improving the sensitivity of THz sensing. The designed metasurface is locally asymmetric, which can induce the high-quality Fano resonance. However, the entire structure is centrosymmetric and thus exhibits polarization-independent characterization. The designed metasurface possesses a polarization-independent resonance peak of transmittance spectrum in 0.1-2THz, which also shows high sensitivity related to ambient refractive index. The advantage of transmitted structure and polarizationindependent resonance can relief the difficulty of measurement. We believe these studies will promote the development of high-sensitivity THz biosensing.
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