基于超表面嵌入结构的高效偏振GaN基LED研究

Thanks to considerable advantages, highly polarized and high brightness light-emitting diodes (LEDs) have promising potential as a key building block in a variety of application fields of advanced information display technology, and high-resolution imaging. However, high-efficiency polarized light sources have not yet been achieved mainly due to the limitation of the properties of active materials in the traditional LED structures. The existing technologies including the incorporation of reflectors, photonic crystals, plasmonic micro-nano-structures, and the addition of polarizers have been attempted to enhance the light emission with the desired polarization direction, but the bottleneck is that the output of the orthogonal state are still suppressed, resulting in an energy loss over 50%. In this project, we propose an alternative methodology to realize high-efficiency polarized GaN-based LEDs by integrating with optical metasurface structures. The selective control of polarization can be realized based on asymmetric transmission and giant optical activity. The theoretical design of metamaterials and fundamental understanding of the physical mechanisms in polarization modulation will be conducted, including the electromagnetic response at two orthogonal directions in the effective media, the energy transfer mechanisms between excitons, photons, and surface plasmons, and the influence of optical localization on the carrier dynamics and quantum efficiency. Through this project, energy-saving GaN-based LEDs with both high polarization and high light output efficiency will be demonstrated by integrating optical metasurface structures based on the existing mature LEDs and micro-processing technologies. This project lies in well with the research scope of the national major research strategy titled “Novel Physics and Applications in Optical Field Modulation and Engineering”. The outcomes of this proposed project will enrich the knowledge of fundamental physics in micro-nano structures and pay new way to achieve high performance and reliable polarized solid state light sources with promising applications in the fields of advanced information display technology and visible light communication.

高偏振、高亮度LED固态光源在信息显示、可见光通信和成像识别等领域具有重要应用价值。传统LED光源受发光材料局限难以实现高效偏振输出，而现有方案仍然难以解决LED高偏振度和低损耗之间的内在矛盾。面向下一代显示技术和可见光通信等发展对高性能固态光源的迫切需求，本项目提出将超表面结构和传统LED相集成，通过构筑新型光场与极化效应，寻求提高偏振度的新方法，如不对称传输、巨大旋光效应对偏振状态的选择性调控等。项目将重点理论设计和优化超表面结构及嵌入方式，揭示有效介质在不同极化方向的电磁响应及偏振调控机制，围绕激子、光子及元激发之间的能量转化，揭示局域耦合效应对发光器件有源层中载流子动力学行为的影响规律，阐述LED偏振和量子效率的增强对超表面的依赖关系，从而实现高效率、高偏振度、低损耗的GaN基LED，在“新型光场调控物理及应用”方面做出基础性创新，并推动其在可见光通信等信息领域的应用。

面向下一代显示技术和可见光通信等发展对高性能固态光源的迫切需求，本项目将超表面等微纳结构和传统LED结构相集成，通过表面、界面结构工程的设计构筑新型极化效应，对出光偏振状态的选择性调控，实现高偏振、高亮度LED固态光源。通过本项目的探索，研究者在微纳结构设计、光场偏振态调控、发光量子效率和器件光学电学特性提升方面取得系列研究进展。主要研究结果包括:（1）具有非对称透射、偏振非对称旋转功能的超表面结构设计与基础理论研究；（2）设计出一种双层平行光栅超构表面结构，嵌入到GaN基LED结构中，通过量子效率和偏振度的有效调控，实现了高亮度、高偏振的绿光输出；（3）设计出一种双层旋转光栅超表面结构，嵌入到GaN基LED结构中，可突破传统50%能量损失的瓶颈，同时实现高偏振度和高内量子效率；（4）制备出不同尺寸的AlGaN基深紫外LED器件，研究了器件光电性能受器件尺寸、界面态等的影响规律。