增益-吸收光学系统中的无损耗表面极化激元及其物理机制研究

Surface plasmon polaritons have significant potential applications in several research fields of nanophotonics. However in many cases, the metallic Ohmic loss narrows the application regime of plasmonic devices. With the development of optical gain media, one of the most promising solutions to this issue is by introducing optical gain to dielectrics adjacent to metals. Although some explorations were carried out previously, a sound theory for perfect compensation to obtain lossless surface polaritons is still absent. In this proposal, we are going to investigate theoretically lossless surface polaritons to emerge at the interfaces between dielectrics with gain and media with loss. For the media with loss, they include two types, i.e., metals and dielectrics. Our preliminary research shows that appropriate gain in dielectrics not only compensate perfectly the Ohmic loss of metals, but also induce a new type of surface state at the interface between gain-dielectrics and loss-dielectrics. The following three aspects will be studied: 1) The lossless surface polaritions at a single interface and their physical mechanisms; 2) The lossless surface polaritions supported by multilayer systems; 3) The lossless surface polaritions supported in cylindrical waveguides. The outcomes of this proposal will improve further the electromagnetic theory about compensating the Ohmic loss by using gain media. What's more, the result will have significance in research of exploring new types of surface polaritons as well as interactions between light and gain/loss media.

表面等离激元在微纳光学等多个领域具有重要的应用前景，然而在很多情况下，金属的欧姆耗散严重限制了相关器件的应用。随着与光增益介质的研究不断取得进展，在与金属相邻的介质中引入增益是解决该耗散的方法之一。然而为获得无损耗表面等离激元，目前的理论框架还不够完善。本项目拟从新的角度对吸收材料/增益介质界面上的无损耗表面等离激元开展理论研究，其中吸收材料包括两种：耗散金属和吸收介质。初步研究表明：合适的增益不仅能完全补偿金属耗散实现无损耗传输，而且和吸收一起可以在介质/介质界面上诱导新的表面模式、蕴含新的物理。本项目具体内容包括：1)单个界面上的无损耗表面等离激元及物理机制；2)多层结构中无损耗表面等离激元的物理特性；3)等离激元圆柱波导及其物理特性。预期成果将进一步完善用增益补偿金属耗散的电磁理论，更重要的是对探索新型表面等离激元、揭示光与增益/吸收介质相关作用具有重要科学意义。

在项目资助下，我们顺利地完成了本项目的研究目标。具体开展的研究内容包括：（a）吸收/增益非厄米光学系统异常电磁特性以及损耗/增益诱导的表面波模式；（b）复共轭超构材料及其异常电磁特性；（c）光/声相位梯度超构光栅异常衍射规律及物理机制。通过研究，我们揭示了吸收金属/增益介质和吸收介质/增益介质界面等体系中无损耗表面等离激元及其物理特性；揭示了复共轭超材料中诸多新颖电磁特性，包括完美吸收和Laser等；揭示了相位梯度超构光栅奇偶性相关的异常衍射现象，发现新的衍射方程，以及揭示了由损耗导致的不对称衍射现象物理机制。取得的研究成果发表在包括Nature Communications、Physical Reviews Letters等高水平期刊上。