Photonic crystals: A novel approach to enhance the light output of scintillation based detectors

摘要

Future high-energy physics (HEP) experiments as well as next generation medical imaging applications are more and more pushing towards better scintillation characteristics. One of the problems in heavy scintillating materials is related to their high electronic density, resulting in a large index of refraction. As a consequence, most of the scintillation light produced in the bulk material is trapped inside the crystal due to total internal reflection. The same problem also occurs with light emitting diodes (LEDs) and has for a long time been considered as a limiting factor for their overall efficiency. Recent studies have shown that those limits can be overcome by means of light scattering effects of photonic crystals (PhCs). In our simulations we could show light yield improvements between 90% and 110% when applying PhC structures to different scintillator materials. To evaluate the results, a PhC modified scintillator was produced in cooperation with the NIL (Nanotechnology Institute of Lyon). By using silicon nitride (Si_3N_4) as a transfer material for the PhC pattern and a 70 nm thick Indium Tin Oxide (ITO) layer for the electrical conductivity during the lithography process, we could successfully fabricate first samples of PhC areas on top of LYSO crystals.