Light extraction enhancement of BGO scintillator by monolayers of SiO2 periodic array

Utilizing the self-assembly method, we have successfully prepared a two-dimensional photonic crystal (PhC) of monolayer SiO2 spheres onto the Bismuth Germinate (Bi4Ge3O12, BGO) crystal and therefore supply another photonic crystal structure with the advantages of low-cost and large-area preparation to improve the light extraction efficiency of scintillator. A light extraction enhancement ratio up to 145.3% as compared the BGO coated by the PhC with the plain reference sample is observed and the underlying mechanism of scintillator light extraction is discussed in detail via a rigorous coupled-wave analysis calculation. The calculated transmission spectra and electric-field distribution exhibit the electric-field eigenmodes confined in SiO2 spheres resonating by the way of whispering gallery modes (WGMs) and becoming leaky modes due to the diffraction effect. Since almost no SiO2 nanospheres over the polystyrene spheres are immersed in preparation, we have demonstrated that the introduction of PhC structures using the SiO2 nanospheres onto the scintillator surface is an effective way to solve the light-trapping problem and therefore the design is very useful to be applied to the particle detection of radiation field.