Improved Light Collection From Inorganic Scintillators Using Photonic Crystals

Typically, current state-of-the-art inorganic scintillation detectors have relatively high light yields. However, a relatively large fraction of that light is not collected due to the high refractive index of the scintillator. Specifically, such high refractive index results in some of the light photons being trapped inside the scintillator due to the total internal reflection, thereby leading to lower detection efficiency and energy resolution. This project focuses on improving the light collection efficiency of high-yield inorganic scintillators by utilizing photonic crystals. The photonic crystals are nanostructures of high refractive index materials, which can provide an ‘optical-bridge’ for light photons to reach the photosensor. Specifically, these nanostructures can be deposited on existing scintillators to increase their light collection efficiency. The project utilizes stochastic simulations and experiments to find optimized photonic crystal geometries for various scintillator-photosensor assemblies. Light transport simulations are carried out in Geant4 and the simulation models have been validated for an 87-nm TiO2 film using data from UV-Vis optical experiments. In the full paper, we will discuss the latest simulation and experimental data in detail, including the optimization simulations for a LYSO scintillator coupled with optimized Si3N4 nanostructures. The resulting geometry will be manufactured and tested to validate the simulation models. Finally, a comparison between a LYSO scintillator with and without an optimized nanostructure will be discussed, including the resulting difference in the light collection efficiency.