双曲超材料复合环栅增强的高频InGaN量子点单光子源研究

Due to the wide adjustable range of bandgap and large exciton binding energy, InGaN quantum dots (QDs) can emit single photon in a wide range from visible to near-infrared and work above liquid nitrogen temperature and even room temperature. It has been one of the most promising candidates for single photon source (SPS). However, the undesirable quantum-confined Stark effect caused by the intrinsic strong polarization field separates the electron and hole wavefunctions and significantly inhibiting the spontaneous emission rate. It is difficult to meet the demand of quantum information which needs high-frequency (above GHz) SPS. Here the hyperbolic metamaterials combined with annular grating was proposed to enhance the repetition rate of InGaN QDs SPS. By combining the broadband enhancement of spontaneous emission from hyperbolic metamaterials and directional light output from annular grating, the problem of limited photon extraction efficiency can also be solved. Based on the previous researches about InGaN QDs SPS, we will study the enhancement mechanism of hyperbolic metamaterials combined with annular grating on spontaneous emission rate, repetition rate and photon collecting efficiency of InGaN QDs SPS from theoretical and experimental analysis. The SPS with repetition rate of more than 1 GHz will be realized, which will provide a novel idea for high-frequency, high-brightness and directional InGaN QDs SPS. The research has widely prospect for many application such as quantum information.

InGaN量子点禁带可调范围宽、激子束缚能大，可实现可见-近红外宽波段上的波长可调单光子发射，并能在液氮温度以上乃至室温工作，是当前最具前途的单光子源之一。然而InGaN材料的固有强极化场会产生量子限制斯塔克效应，导致电子-空穴波函数分离，使自发辐射速率受到抑制，难以达到量子信息对GHz以上高频发射的要求。本项目提出利用双曲超材料复合环栅结构来提升InGaN量子点单光子源的重复频率。在利用双曲超材料宽带自发辐射增强特性的同时，结合环形光栅的定向耦合输出特性解决其光出射效率低的问题。在前期已制备出的InGaN量子点单光子源基础上，围绕双曲超材料复合环栅对InGaN量子点自发辐射速率、重复频率和光收集效率的提升机理及器件制备展开理论和实验研究，从而实现重复频率1 GHz以上的单光子源。将为实现高频、高亮度、定向发射的InGaN量子点单光子源提供一条新思路，在未来量子信息等领域有着广阔应用前景。

InGaN量子点禁带可调范围宽、激子束缚能大，可实现可见-近红外宽波段上的波长可调单光子发射，并能在液氮温度以上乃至室温工作，是当前最具前途的单光子源之一。然而InGaN材料的固有强极化场会产生量子限制斯塔克效应，导致电子-空穴波函数分离，使自发辐射速率受到抑制，难以达到量子信息对GHz以上高频发射的要求。本项目提出利用双曲超材料复合环栅结构来提升InGaN量子点单光子源的重复频率。设计并制备出基于Ag/SiO2、Ag/TiO2、Al/SiO2不同材料体系结构的双曲超材料，获得其对InGaN和GaN量子点在300nm~800nm宽波段的自发辐射增强机理，揭示了金属-介质纳米多层界面上SPP模式相互耦合产生宽带自发辐射增强效应的机制，发现增强带宽和强度可由双曲超材料结构参数进行调节，最大Purcell因子达到80，增强带宽达到400nm；基于400~700nm不同波段的胶体量子点实验验证了双曲超材料的宽带自发辐射增强效果，实现荧光增强达到6倍以上，寿命减小1倍以上。完成大面积InGaN量子点耦合GaN纳米线和GaN量子盘耦合AlGaN纳米线阵列制备，最细直径仅10nm，发射波段分别位于386nm和330nm；设计并制备出双曲超材料耦合InGaN自组织量子点结构，与无耦合结构相比，平均荧光寿命从约2.2ns降低至约0.2ns，对应重复频率提升到1.67GHz。实现双曲超材料耦合图形化光栅衬底的InGaN自组织量子点结构，与无耦合结构相比，荧光强度增强达到11 倍。实现10K温度下InGaN量子点/纳米线单光子发射，发射波段380nm，二阶相关系数g(2)(0)=0.05；实现基于AlGaN薄膜中原子缺陷的高亮度室温单光子发射，发射波段从700~960nm，二阶相关系数g2(0)最小达到0.24，光子计数器实际收集到的荧光强度达到280 kcps，且具备良好的偏振发射特性，偏振度达到93%。本项目研究的单光子源在高安全性量子通信、量子身份认证、量子精密传感测量等领域可作为核心量子光源与纳米传感器，有望应用于国防和国家安全领域中重要指令与信息的高安全性传输、重要装备使用人员的高安全性身份认证以及高精度惯性导航。