基于金属表面等离子体效应的平板光学元件的设计、制作和表征

Recent researches have demonstrated that very thin metallic subwavelength antenna arrays can modulate the field amplitude and phase abruptly based on the surface plasmonic resonance effect. In this project, firstly, we develop a complementary structure to modulate the field amplitude and phase, i.e., the metallic thin film with subwavelength antenna air holes, and then investigate the general modulation rules. The complementary structure has such advantages as easy fabrication, low background noise, etc. Secondly, by means of the phase modulation mechanism, we propose a new method for designing optical elements. The designed optical elements include the spectrum-splitting and beam-concentration element, the long-focal-depth lens, the multi-focus lens, the beam-shaping element, etc. The designed optical elements will be manufactured by using the micro fabrication technology and their performance will be characterized in experiments. It will promote the wide practical applications of this kind of optical elements. Thirdly, the amplitude modulation mechanism of the metallic subwavelength antenna holes will be employed to improve the performance of the designed optical elements, for instance, to increase the focusing efficiency and resolution or to decrease the noise. It is worth mentioning that the designed optical elements are about 50nm thick, since the field amplitude and phase modulation originates from the electromagnetic resonance on the metal surface. Therefore, we call them as planar optical elements. This project will significantly promote the light weight, miniaturization and integration of optical elements.

最近研究表明，基于表面等离子体共振效应，薄层金属亚波长天线阵列结构(或称为正结构)可对光场的振幅和相位产生突变调制。在本项目中，第一，发展了一种反结构，即在薄层金属上刻蚀出镂空天线孔阵列结构，并研究其对光场的振幅和相位的调制规律。这种反结构具有减小加工难度、降低背景噪音等优势。第二，基于这种相位调制机制，提出了一种光学元件设计的新方法。通过运用该方法设计分色聚焦光学元件、长焦深透镜、多焦点聚焦透镜、束整形元件等，并利用微加工技术进行制作及实验表征，推动这类光学元件走向广泛的实际应用。第三，利用金属亚波长结构对光场的振幅的调制，改善所设计的光学元件的性能，比如提高聚焦效率、增强聚焦分辨率或降低噪音。特别值得一提的是，由于光场的振幅和相位的调制来源于金属表面内的电磁共振，所设计的光学元件很薄(约50nm)，故又称为平板光学元件。本项目的实施，将极大地推动光学元件的轻型化、微型化和集成化。

金属超表面结构由薄层金属亚波长天线阵列 (或称为正结构) 组成，可对光场的振幅和相位产生突变调制。在本项目中，首先，提出了平板光学元件设计的新方法，设计了多种功能的平板光学元件，比如波分复用全息光学元件、多焦点聚焦透镜、偏振控制器、自旋分离聚焦器件、产生特殊光束的全息元件等；其次，发展了一种反结构，即在薄层金属上刻蚀出镂空天线孔阵列结构，并探索了提高超表面器件效率的多种方案，大幅度提高了超表面器件的效率 (理论效率由20%提高到90%以上，实验效率由5%提高到80%以上)。最后，利用微加工技术制作了超表面器件，搭建了实验系统对超表面器件的性能进行了定量测量，实验测量结果很好地验证了理论模拟结果。本项目的实施，推动了光学元件的轻型化、微型化和集成化应用。