利用人工微结构实现闪烁体光提取效率的提高和发光方向性的调控

Scintillation detection systems play an important role in the radiation measurement in high-energy physics experiments, nuclear physics experiments, and medical imaging systems.The scintillators with high efficiency are very crucial factor for the improvement of detection system. Due to total internal reflection with the high refractive index of scintillators, the light extraction efficiency is very low, which reduces the effective light yield (absolute light yield multiplied by the light extraction efficiency). This proposal aims to improve the light extraction efficiency and control the directionality of luminescence of scintillators using artificial photonic microstructures based on self-assembled microspheres. The main content is to understand the physical mechanism of light extraction and controlling the directionality of luminescence for the typical thin and bulk scintillators, to build the design principles based on the requirements in detection systems, to explore the method to construct photonic structures on the scintillators with high-quality and large area. Compared with the traditional research method for scintillators focused on the material chemical composition and crystal structure to improve the absolute light yield, the innovation of the present proposal is to develop scintillators with the principle of nanophotonics. Improved light extraction and controlling the directionality of luminescence can be achieved by the coupling of the evanescent waves with photonic microstructures at the outgoing interface, which is also considered as an improved utilization of scintillation photons.

闪烁探测系统在高能物理实验、核物理实验和核医学成像领域的辐射测量中具有重要地位。闪烁体的效率是提高探测系统性能的关键，由于闪烁体的高折射率引起的全内反射限制了闪烁光子的出射，导致了光提取效率的低下，降低了闪烁体的有效光产额（绝对光产额乘以光提取效率）。本项目拟研究利用人工微结构实现闪烁体光提取效率提高和发光方向性调控的方法。将以薄膜和块体闪烁体为研究对象，深入研究以自组装微球为基础的人工微结构提高发光提取效率和调控发光方向性的物理机制，结合闪烁探测需求探讨设计原则，建立光提取和方向性调控的物理模型，研究在闪烁体上制备高质量大面积微结构的方法，为辐射探测应用打下基础。与传统闪烁体研究主要关注材料化学组分和晶体结构以提高绝对光产额不同，本项目的创新点是基于微纳光子学的基本原理，利用光子人工微结构与全反射光在界面形成的衰逝波的耦合，实现全内反射光的有效提取和发射方向性的调控。

闪烁探测系统在核物理实验、核医学成像、国家安全等领域具有重要用途。但由于闪烁体的高折射率引起的全内反射，限制了闪烁光子的出射，导致了光提取效率的低下，降低了闪烁体的有效光产额，从而影响了探测系统性能的提高。本项目基于光子人工结构调控闪烁体的发光，从而提高闪烁体的性质，进而提高探测系统的性能。项目取得了以下主要成果：1）利用光子晶体实现闪烁体光输出的显著提高，根据不同的结构特征、制备方法和样品尺寸，获得了光输出50%-250%的提高。2）采用基于光子晶体导模共振原理实现了闪烁薄膜或闪烁移波薄膜的方向性调控。3）通过光子晶体提高闪烁体光输出效率，从而降低了光子统计学波动，从而提升了闪烁系统的伽马射线能量分辨率约10%。4）通过光子晶体提高闪烁体光输出效率和降低闪烁光在闪烁体内的时间弥散，提高了探测系统时间分辨率约18%。5）研制了大面积光子晶体闪烁体，在特定角度上提高光输出120%，显著提高了探测系统的灵敏度和信噪比，在国防领域重大科学试验中发挥了关键作用。该项目首次将微纳光子学领域的最新成果应用于核辐射探测领域，属于新兴交叉学科研究方向，该方向的研究成果将为核辐射探测领域的发展注入新的活力，产生突破性的发展方法。