光路可逆相位梯度超表面及其在隐身技术中的应用研究

Phase gradient metasurface(PGM) is the two-dimensional metamaterial, which can achieve the manipulation of the propagation direction, wave-front and polarization of the electromagnetic waves with more freedom by using the periodic or quasi-periodic sub-wavelength unit cell arrays. By using the PGM, a lot of functions of the conventional optical devices can be realized, such as: surface electromagnetic wave coupling, beam focusing, imaging, polarization conversion and so on, and the thickness and volume of the devices can be highly decreased. However, compared with the traditional devices, the light path may be irreversible when the PGM is applied to the manipulation of the electromagnetic wave, which seriously impacted the study and application of the PGM. Aimed at this problem, the possible reasons for the irreversible optical path of the PGM are theoretically analyzed. The physical mechanism of the PGM with reversible optical path is studied. The realization principles and methods of the PGMs with reversible optical path are studied. The mechanism for the omni-directional stealth technology based on the PGM with reversible optical path is studied. The radar cross section (RCS) reduction principles of the anomalous reflection, surface wave excitation, diffuse reflection and polarization conversion for the PGM are studied, respectively. The principles and methods for the phase gradient design and optimization and operation bandwidth extension of the omni-directional stealth metasurface are studied. The anomalous reflection spectra and RCS of the optimized omni-directional stealth metasurface are measured to verify the reversible optical path and the omni-directional stealth performance, respectively.

相位梯度超表面是一种二维超材料，通过周期或准周期的亚波长结构单元阵列可以实现电磁波传播方向、波阵面、极化方式的自由调控。利用相位梯度超表面实现传统光学器件的功能：如耦合表面波、聚焦、成像、极化转化等，可以极大地降低器件的厚度和体积。但与传统器件相比，相位梯度超表面存在光路不可逆的问题，严重影响其研究和应用。 本申请针对相位梯度超表面的光路不可逆问题，分析相位梯度超表面光路不可逆的主要原因，研究可逆相位梯度超表面的物理机制，实现方法。研究基于光路可逆相位梯度超表面的全向隐身机制，分别研究超表面异常反射、耦合表面电磁波、漫反射和极化转化实现RCS缩减的原理。研究全向隐身超表面相位梯度设计与优化的一般方法和原理，研究全向隐身超表面的带宽拓展方法，通过优化设计得到性能优越的全向隐身超表面，测试其异常反射谱验证光路可逆特性，对比测试全向隐身超表面及同尺寸金属板的RCS，验证其全向隐身性能。

本项目围绕光路可逆相位梯度超表面理论、设计方法及其在隐身技术中的应用展开研究，阐明了光路可逆相位梯度超表面的物理机制，通过超表面单元设计理论及工作带宽拓展机理的研究，建立了超表面的设计方法及工作带宽拓展方法；提出了基于光路可逆相位梯度超表面的全向隐身技术。设计、仿真、优化、制备了平板型和柱形共形全向隐身超表面，通过单站RCS仿真、测试完成了原理验证。在此基础上，提出了基于人工表面等离激元模式的传输相位调控机理，分别实现了基于人工表面等离激元的色散相位梯度超表面、极化转换超表面、各向异性编码超表面、吸透一体频率选择超表面。提出并验证了基于超表面相位梯度设计的宽角域RCS增强技术。提出并验证了圆极化旋向选择吸收相位梯度超表面。所有研究成果在电磁波散射调控中具有重要的应用前景。