基于梯度折射率(GRIN)介质构成的平焦面龙伯透镜，具有大视场无像差成像特性。在微波频段该结构已广泛用作高增益广角天线，然而在光频段由于缺乏三维GRIN等效介质的高精度、高保真制备技术，阻碍了该器件在光学成像领域的应用。本项目针对当前光频段平焦面龙伯透镜存在的三维制备难、视场有限及工作波段单一等若干关键科学问题，发展一种空间连续梯度变化结构的高精度、高保真三维制备技术：采用灰度双光子3D打印制备光波长尺度结构连续梯度变化的聚合物超材料骨架，结合原子层沉积技术对骨架表面共形覆盖高折射率介质，实现高折射率梯度、光频段响应的三维、GRIN等效介质。通过建立一套结构设计-灰度3D打印工艺-器件性能协同优化机制和方法，制备出光频段三维平焦面龙伯透镜器件，研制的透镜工作于红外或可见光频段，视场角>120°，具有平场消球差特性，上述研究为其在微小光学、集成光学和纳米光子学中的应用提供重要科学与技术基础。

The flat Luneburg lenses design by graded-index (GRIN) medium have the excellent characteristics with wide field-of-view (FOV) and aberration-free imaging. This lens structure has been widely used as a high-gain wide-angle antenna at microwave frequencies. However, the application of the lens device at optical frequencies in the field of optical imaging is limited, due to the lack of high-precision, high-fidelity fabricating technology of the three-dimensional (3D) GRIN effective medium. This project will focus on current key technical problems such as the difficulty of 3D fabrication, limited FOV, and narrow working band for the flat Luneburg lens structures at optical frequencies based on GRIN metamaterials, to develop a high-precision, high-fidelity 3D fabrication technology for spatially continuous gradient changing structures. In this project, we will fabricate 3D polymer metamaterials with continuous gradient changes of structural parameters by two-photon 3D printing using real-time gray-scale exposure, and conformally deposit high-refractive-index TiO2 dielectric layer on specially designed 3D metamaterial surface by atomic layer deposition (ALD) technology, to realize the GRIN effective medium with high-refractive-index change at optical frequencies. We will establish a set of co-optimization mechanisms and methods for structural design / grayscale 3D printing process / device performance, and finally fabricate a prototype 3D flat-plate Luneburg lens device at optical frequencies. The fabricated lenses will work in the infrared or visible light band, and have a series of characteristics such as a field-of-view of > 120° and aberration-free feature. The above research provides the important scientific and technical foundations for its applications in micro-optics, integrated optics and nano-photonics.