双面柔性超材料在宽带太赫兹波自由空间隐身器件中的应用研究

The invisibility cloaking technology of metamaterial under terahertz frequency has the functionality of the significant strategy. It has been expected to be used in the military and civil areas. However, strict requirement of material on free space invisibility cloak are demanded, resulting in difficult design and manufacture. Besides, the problem of bandwidth, impedance mismatching, and simplification of structure parameters decreases the function of invisibility. The quasi invisible functionality on terahertz frequency is realized in carpet cloaking. Most of metamaterial invisibility cloaks were prepared with some solid material, which limited their practical applications in soft stealth components. This project aims to explore a new kind of broadband soft double-faced metamaterial to be used in terahertz free space invisibility cloak. By adjusting geometric construction of double-faced split ring resonantor, combining experiment and theoretical simulation of the material effective parameters, the relationship between the composition, structure and properties is analyzed. Effective permittivity and permeability under terahertz frequency can be obtained. In addition, the invisibility cloak is established by using discretization method. In order to solve the impedance mismatching, the broadband antireflective tapered microstructure will be designed. To realize non-polarization characteristics, the orthogonal array configuration of metamaterial is designed. The preparation of the metamaterial of metal split ring resonantor is explored to obtain a flexible invisibility device. It is believed that the study of this project can promote the design and development of new metamaterial invisibility cloak and related devices.

太赫兹波超材料隐身技术及器件具有广阔应用前景。但自由空间隐身器件对材料要求苛刻，难于设计和制备，并且共振带宽、阻抗失配、偏振敏感等问题导致隐形性能大大降低，国际上仅在地毯式半空间隐身斗篷中实现了反射式准隐形功能。传统硬质材料隐身结构，限制了其作为柔软隐形罩的实际应用。本项目拟开展新型双面多层柔性超材料的设计与制备研究，实现在宽带太赫兹波自由空间隐身器件中的应用。通过对双面多层开口谐振环复合超材料结构的优化，实验和理论模拟相结合，解析材料组成-结构-性能之间的变化规律，提高太赫兹波等效参数带宽。构建圆柱型自由空间隐形器件离散化模型，研究隐身器件所需材料参数分布规律的双面柔性超材料结构。采用宽带增透锥形微结构解决材料参数简化引起的阻抗失配问题，设计正交型超材料阵列排布，探索非偏振等效参数特性。研究超材料的光刻制备工艺，最终获得用于宽带太赫兹波自由空间隐身器件的双面多层柔性超材料。

隐身技术是现代军事中具有巨大战术价值和战略威慑作用的一项技术。近几年来，超材料在隐身领域的研究也受到了广泛的关注，利用超材料不同的物理性质可以实现不同物理机制的隐身。构建圆柱型自由空间隐形器件离散化模型，获得等效材料参数离散化分布规律。优化设计金属铜开口谐振环柔性超材料复合结构，探索获得宽带太赫兹波段 (0.2THz-1.0THz)等效介电常数和等效磁导率的超材料阵列结构，实现隐形器件所需的材料参数分布特性。研究了隐身器件用的超材料结构的等效参数提取方法，只有准确地提取等效参数，才能准确地设计宽带柔性超材料结构用于隐身器件。我们通过反射和透射系数来提取双各向异性开口环形谐振器（SRR）平板超材料的等效参数的一种直接而又稳定的方法。基于双层超材料耦合的太赫兹波段宽带线偏振转换器，可以在0.73到1.41THz的范围内将线偏振入射波的振动方向旋转90°，且保持偏振转换率高于90%。基于各向异性偏振转换超材料的宽带太赫兹半波片，可以在0.64到1.67THz的范围内将线偏振入射波的振动方向旋转2的角度，并保持偏振转换率高于85%。项目研究为今后在理论上设计和实验制备其他超材料隐身器件提供科学基础和技术参考，推动变换光学理论应用研究的发展，并将在军事和民用领域具有潜在的应用前景。