吸波新型人工电磁介质基础与应用研究

Metamaterial absorbers are the research object of the young scientist fund of NSFC undertook by the applicant. Important progresses have been made. The insight of the mechanism of metamaterial absorbers has been deepened further. We have suggested that a zero-index layer of arbitrary thickness can perfectly (100%) absorb an incident wave. Excellent works have been made in the research of absorbing functions. We have found that wide-band absorption can be realized by incorporating several resonators of neighboring resonant frequencies into a unit of metamaterial absorbers. And, the preliminary exploration of different absorbing forms and application values have also been made for metamaterial absorbers. Outstandingly, we have suggested that it is possible to realize a terahertz electric modulator of large modulation ratio based on a metamaterial absorber. Based on the above research, ten SCI papers have been published, of which most are published on high-quality journals such as Nano Letters and Applied Physics Letters. In the current project, the important directions in the previous project will continue to be researched and moved forward, new connotation in the absorbing of metamaterials will be explored, and the application research will be placed on an important position and get more attention. In the research of absorbing functions, simple metamaterial absorbers of wide-band absorption will be designed and optimized. The absorbing processes inside the metamaterial absorbers will be investigated and controlled, and new absorbing forms of different mechanisms will be explored, including realizing ultra-small absorbing hot points, enhancing the absorption of active materials, realizing nonlinear absorption, and realizing classic analog of electromagnetic induced absorption and single patterned metallic film of strong absorption. The application of metamaterial absorbers in the photon-heat and photon-electron areas will be explored, including manipulating the far-field thermal radiation and enhancing near-field thermal radiation, improving the performance and compact integration of optical detectors and modulators.

所承担的青年科学基金项目围绕吸波新型人工电磁介质展开研究，已取得重要进展。深化了吸波机理理解，提出任意薄的零折射率层能完美地吸波。在吸波性能研究方面做出突出工作，发现在结构单元内引入多个共振频率相邻的谐振子可实现宽带吸波。初步探索了其它类型的吸波方式和吸波人工电磁介质的应用，特别是提出了利用吸波能实现具有大调制比的电控太赫兹调制器。已发表10篇SCI论文，多发表在Nano Lett.、APL等主流期刊上。在本项目中，以前的重要研究内容继续深化，并扩展吸波的新内涵，突出吸波应用。在吸波性能研究方面实现宽带吸波的简单结构。调控结构内部的吸波过程，探索其它吸波方式，如实现超小吸波热点，增强活性材料的吸收，研究非线性吸波，实现电磁诱导吸收的经典类比，实现强吸收的单层金属微结构。探索吸波人工电磁介质在光热、光电这两方面的应用，如调控远场热辐射、增强近场热辐射，提高光探测器、光调制器的性能和紧凑性。

吸波是一种基本的光学现象，有广泛而重要的应用，如电磁隐身、光探测、信号调制、传感和太阳能等。新型人工电磁介质为光吸收提供了灵活、有效的新途径，如超宽的吸波带宽、灵活可调的工作频段、超薄结构、亚波长尺寸的吸波单元等。项目组就基于新型人工电磁介质吸波的各个基础方面展开了研究，包括机理、性能、内涵扩展及应用等，其中吸波带宽控制是重点（这对吸波应用是非常关键的），取得了多个创新成果。除了用于光频段，这些发现可扩展地运用到红外、太赫兹等其它频段。我们从不同机制和材料出发实现了多种宽带吸波结构，如通过引入金属、介质多层结构代替渐变结构中的均匀有损材料获得薄而超宽带的光吸收器，这是当前最有效的吸波手段之一；基于耐高温的石墨，利用渐变结构和纳米线的结合获得宽带光吸收；发现在金属反射基底的基础上单纯利用损耗介质也能获得宽带吸波，且能具有带通吸波的效果；利用金属/介质多层结构获得宽带对光吸收，这便于大尺度制备；利用高损金属代替通常所用的金属，使得简单的微结构也能宽带吸波，这也便于实验制备。这些成果在实际应用中能发挥重要作用，如能为电磁屏蔽提供有效的吸波手段；为热光伏、光热生成等太阳能利用提供有效的带通吸波手段，也能提供耐高温的手段；为探测器提供有效增强活性材料的对光吸收的新手段。我们探索了几种实现窄带吸波的方法，如利用介质共振粒子辅助增强光吸收，利用具有高Q值的金属微结构的特殊共振模式，以及利用共振粒子的集合响应。这些可应用于窄带热辐射、探测器和调制器以及灵敏的传感器等领域。我们也扩展了吸波所常用的微结构的内涵，如利用金属反射基层加金属微结构在多个频率处同时获得强局域场，用以提高光谱传感的敏感性，也利用这种结构体系进行相位调控，从而获得超薄的宽带半波片。这方面的研究预示着吸波结构有着很多潜在的可能。