Ultra-thin high-reflector film designed for LYSO scintillators

Abstract

The reflectivity and thickness of optical reflector used in scintillator array influence the performance of PET detector module. In this paper, we designed an ultra-thin multilayer high-reflectivity (HR) film and coated it on the surfaces of ultra-precision polished LYSO scintillators. The HR film consists of three quarter wavelength reflective films with the central wavelengths set at 365nm, 430nm and 570nm respectively. Thus, the reflectivity spectrum of the HR film matches the emission spectrum of the LYSO scintillator. The LYSO samples were polished (surface roughness Ra=0.57nm) before coating. 48-layer TiO 2 /SiO 2 /HfO 2 were deposited on LYSO alternately by electron beam evaporation. The total thickness of HR film was about 3μm. The average reflectivity of HR film at 360-620nm range was 99.50% at 8° incident angle. In conclusion, this study demonstrates a novel HR film design with excellent performances. This HR film technology can be applied to design preclinical PET detectors with high filling factor (and sensitivity).