Photonic Crystal Slabs Applied to Inorganic Scintillators

The extraction of scintillation light from an inorganic scintillator is one of the major bottlenecks in time-of-flight positron emission tomography (ToF-PET) because it directly affects the energy and time resolution of the gamma detector. To increase the light extraction efficiency, we use photonic crystal slabs (PCS), defined as thin dielectric layers structured with a 2-D, or 3-D, periodic pattern. A higher light output, combined with a reduction of the average path length traversed by the photons in the crystal before extraction, leads to a more precise evaluation of the particle time detection. This also implies a better coincidence time resolution (CTR). These improvements translate to ToF-PET reconstructed images with a higher signal-to-noise ratio and lead to more accurate diagnoses, faster exams, and possibly a reduced patient radiation dose. In this paper, we present the results obtained using lutetium-yttrium oxyorthosilicate, Lu2(1-x)Y2xSiO5 samples patterned with nanoimprinted PCS. Comparative light yield (LY) measurements show an improvement of a factor 1.68 for a naked configuration, whereas CTR goes from 535 to 315 ps.