In the past decade, metamaterial absorber has been attracting great attention and making huge progress. Most of previous metamaterial absorbers are working with a narrow band. Some efforts to realize broadband absorber have been made from microwave, terahertz to optical frequencies, which often includes multiple resonators with different sizes or multilayer structure with different geometrical dimensions. The configurations of these designs are not simple, and they require some complicated fabrication procedures. Meanwhile, the position of absorption peak and working intensity are usually fixed once the structure of metamaterial absorber is fabricated. Here a new isotropic tunable absorber is presented with a simple vanadium dioxide structure in the terahertz region. By adjusting the geometrical size, simulation shows that our design under normal incidence can achieve broadband absorptance >90% with a central frequency of 1.815 THz in the frequency band of 1.08–2.55 THz. Working intensity of the proposed absorber can be tuned from 1.3% to near 100% by changing the conductivity of vanadium dioxide from $\text{0}\;{\Omega ^{ - 1}}\text{cm}^{ - 1}$ to $\text{2000}\;{\Omega ^{ - 1}}\text{cm}^{ - 1}$. The obtained absorption spectrum is independent of incident polarization, and absorptance has a good performance when incident angle varies from ${\text{0}^\circ }$ to ${\text{45}^\circ }$. The proposed design may be useful for promising applications in stealth technology, thermal emitter, and terahertz detection.

中文翻译：

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具有相变材料 VO$_2$ 的可调各向同性吸收器

在过去的十年中，超材料吸收体受到了极大的关注并取得了巨大的进步。大多数以前的超材料吸收器都使用窄带。从微波、太赫兹到光学频率，已经为实现宽带吸收器做出了一些努力，这通常包括具有不同尺寸的多个谐振器或具有不同几何尺寸的多层结构。这些设计的配置并不简单，它们需要一些复杂的制造程序。同时，一旦制造出超材料吸收体的结构，吸收峰的位置和工作强度通常是固定的。这里展示了一种新的各向同性可调吸收器，其在太赫兹区域具有简单的二氧化钒结构。通过调整几何尺寸，模拟表明，我们的设计在垂直入射下可以在 1.08-2.55 THz 的频带内以 1.815 THz 的中心频率实现大于 90% 的宽带吸收率。通过改变二氧化钒的电导率，所提出的吸收剂的工作强度可以从 1.3% 调整到接近 100%$\text{0}\;{\Omega ^{ - 1}}\text{cm}^{ - 1}$ 至 $\text{2000}\;{\Omega ^{ - 1}}\text{cm}^{ - 1}$. 获得的吸收光谱与入射偏振无关，当入射角从${\text{0}^\circ }$ 至 ${\text{45}^\circ }$. 所提出的设计可能对隐身技术、热发射器和太赫兹探测等有前景的应用有用。