基于变换光学的三维隐身与亚波长成像技术的新理论研究

Transformation optics has played a key in the development of metamaterial field. Invisible cloak and subwavelength image are among the hottest research topics in the field of metamaterials and have triggered extensive explorations for their important applications in both military and civilian fields. Till date their physical fundaments and technological potentials have been thoroughly discussed and verified by numerous theoretical and experimental evidences. However, many practical problems remain in their current stage and need further in-depth investigations to uncover or solve them. In this project, we will investigate both three dimensional cloak and sublwavelenth imaging and develop new theories to push them more realizable toward the final target of practical application. To solve the problems in material fabrication faced by the traditional cloaking approach, we will propose two alternative designing approaches and verify them experimentally in the end. First we will construct a non-Euclidian optical transformation technique to design a singularity-free invisible cloak. New parametrical degrees of freedom will be introduced in our theory and help modify the index distributions of the cloaking media involved in the process of transformation or post-transformation. Besides this, three dimensional quasi-conformal transformation technique will be developed as a second promising approach to achieve a weakly anisotropic cloak without singularity. Multistep discrete transformation techniques are going to be created and formulated to construct the key coordinate mapping algorithm, which will be a real challenge needing comprehensive mathematical solutions. Regarding previous subwavelenth imaging techniques which are commonly suffered from fabrication and application challenges, we will explore a different but more rubost approach to achieve wave-unlimited imaging based on the mirrored Maxwell's fisheye lens. In this project we will give in-depth explorations to understand the superresolution mechanism and clear the disagreements with consistent arguments. Once solving this, we will take a further step to design and fabricate Maxwell's fisheye imaging systems. The frequency domain in experiment will be shifted from microwave to visible light to examine conception and application feasibility. We have done preliminary investigations for the above research contents and established the preliminary technological diagrams. It can be highly anticipated that our research will achieve meaningful breakthrough in 3D cloaking and subwavelenth imaging that will definitely pave the way for their future development toward the final destiny of practical application.

变换光学技术具有超强的光路设计和波的调控能力，在电磁隐身等特异介质研究领域发挥着重要作用。本项目将通过变换光学理论的创新研究，来解决目前电磁隐身和亚波长成像技术在理论和应用上面临的瓶颈，为这些重要技术的发展探寻更具实验可行化的新方案。针对目前隐身介质的材料制备难点，本项目将深度开拓非欧氏空间变换理论，来设计无奇点隐身介质，通过引入新自由度参量来合理化其材料参数分布；同时将开启三维拟保形变换的基础理论研究，首度建立真正的地毯式三维半空间隐身技术。为超越以往特异介质透镜的材料和应用局限，本项目将主要研究基于变换光学的Maxwell鱼眼透镜这一新型远场亚波长成像技术，深入解析其超分辨成像机理，利用变换光学、逆散射等技术原理来设计制备Maxwell鱼眼透镜介质体系，并进行关键的光波段应用研究。本项目将极有希望在三维隐身和亚波长成像的理论和实验研究上取得重要进展。

变换光学技术与超构材料发展让电磁隐身等具有颠覆性应用前景的新技术变为可能，同时也给亚波长成像和聚焦带来新的实现方案，但它们在实际应用上有诸多问题与挑战需要克服。在本项目里面：（1）我们首先针对各向异性变换光学隐身衣的制备难点，着力发展了基于保形变换法构造各向同性隐身衣的新理论，通过结构设计与材料参数控制，让各向同性介质首次可以实现波动光学下的完美隐身效果。在理论研究基础上，我们进行了实验工作并证实了理论的有效性，为隐身衣理论完善与发展起到了一定的推动作用。另外，我们也在电磁隐身衣的构造技术上进行了深入研究，于业内首次利用聚合物材料分别制备了准保形三维地毯式隐身衣和拓扑优化单项隐身衣，这些结果为隐身技术的局部应用提供了有效选择方案；（2）开展了三维磁场隐身研究，利用超导与铁磁材料的巧妙结合构造出了0-250kHz宽频率响应磁场隐身罩，研究结果首次让金属反电磁感应探测技术变为可能。其后通过改进设计，利用金属本身的抗磁特性实现了室温下的金属反探测效果。这方面研究成果极有望让隐身从前沿研究真正走向技术应用；（3）把变换光学拓展到热力学领域，利用人工热学材料实现了具有瞬态热流隐身效果的人工热学器件，并通过耦合电流方程，首次实验演示了具有热-电双物理场效应的多功能隐身器件，这些成果为热能操控与利用研究提供了新的技术途径和方案；（4）利用变换光学手段设计出了理想的鱼眼透镜用探测器，仿真结果证实了它在密闭型渐变折射率透镜的普适应用性及相应的远场亚波长聚焦功能；我们也基于超表面技术，设计并实验演示了具有近场电磁波操纵功能的平面透镜，实现了对磁偶极子场的亚波长聚焦效果；另外我们也研究了超透镜在三维成像时的景深问题，发现成像物体的前后端图像信息会相互干扰这一固有缺陷。这些研究成果对于隐身概念的发展与应用以及亚波长成像发展具有较大的促进作用，部分成果项目负责人以第一或通讯身份发表在Nature Communications、Physical Review Letters和NPG Asia Materials等权威期刊之上，获得了Nature News、Physics Org和Popular Mechanics等众多国内外知名学术媒体的传播报道。