近红外透明导电氧化物超透镜研究

Decay of evanescent waves can be effectively suppressed by surface plasmon polaritons on the surface of metals, which makes the superlenses go beyond the diffraction limit, though the resolution is limited by the loss of metals. In order to explore the novel materials for near-infrared superlenses and further improve their resolution, this project plans to prepare the transparent conducting oxides (TCOs, such as ITO, AZO, and GZO) with the tunable optical properties using magnetron sputtering and doping. Since the real part of the TCOs permittivity is either negative or positive with a low loss in the near-infrared, the superlens with a resolution superior to 1/14 of wavelength can be realized based on the all-TCOs structures. The electric control and the hyperlens originating from the hyperbolic dispersion will be also studied. With the aid of numerical calculations, magnetron sputtering, micro/nanofabrication, and near-field probing, the influences of the properties of TCOs on superlensing wavelength, resolution will be investigated as well as the electric-field tunability and the possibility of propagating waves converted from evanesent waves. This study benefits to overcome the resolution and the brightness limit of metallic superlenses and improve the near-infrared spctroscopy and imaging, which may accelerate the material, the biological, and the medicical research.

利用金属材料表面等离子体共振可有效抑制倏逝波衰减，获得可突破衍射极限的深亚波长分辨超透镜，但其分辨率受制于金属本身的损耗。为探索新型超透镜材料体系，进一步提高近红外超透镜分辨率，本项目计划研究利用磁控溅射和掺杂技术制备光电性质可调的透明导电氧化物（ITO、AZO和GZO等），利用其近红外低损耗和介电常数实部可正可负的特点，实现完全基于叠层透明导电氧化物材料的分辨率优于1/14波长的近红外超透镜。在此基础上进一步探索透镜的电场调控，以及基于双曲色散的双曲透镜远场成像。通过数值模拟设计、磁控溅射、微纳加工和近场探测等理论和实验手段，揭示透明导电氧化物材料特性与近红外超透镜工作波长、分辨能力之间的关系，电场对它们的影响，探索将近场倏逝波转换为传导播波的可能性。通过本研究有助于克服金属超透镜损耗导致的分辨率和光亮度限制，显著提升红外光谱成像质量，促进材料、生物和医药研究。

利用金属表面产生的等离子共振可以获得突破衍射极限的深亚波长分辨超透镜，但是分辨率受制于金属本身的损耗。为了进一步提高近红外超透镜分辨率，本项目利用重掺杂半导体近红外低损耗及介电常数实部可正可负的特点，选择了ZnO基材料，完成了三方面研究：（1）制备了氧化锌基透明导电氧化物，系统研究了掺杂对于载流子浓度、电阻率、载流子迁移率和复介电常数之间的关系，实现了对其在近红外波段等离子体共振峰位的调控；（2）基于所获得的氧化锌基透明导电氧化物薄膜，利用传输矩阵法和有限元方法对单、多层薄膜结构中的倏逝波传播特性进行了研究，提出了可用于近红外波段分辨率高达1/20波长的透明导电氧化物结构，阐明了材料损耗、超透镜分辨率和工作波长之间的关系；（3）研究发现利用超薄金属叠层结构可进一步降低损耗，从而改善倏逝波的传播，提升图像分辨率。本项目提供了重掺杂半导体代替金属制备红外超透镜的可行性，实验方法、理论研究及测试结果，为红外超透镜的应用提供条件。