Description

In recent years, renewed interest has been directed toward up-conversion devices and materials. The interest is principally due to prospects for the realization of infrared up-conversion lasers pumped with laser diodes. The revival of interest for the up-conversion phenomenon is due to the advent of efficient and less costly that can be used as excitation sources and the appearance of new materials such as Calcium Silicates and BaSrCeO4. We will discuss the applications of such materials in printing inks and plastics that would frustrate the activities of forgers and counterfeiters. Apart from applications in currency printing, there are many other fields in which upconversion phosphors can play a part, including original works of art, passports and credit cards. Up-conversion phosphors are special kind of material. The interesting feature of these materials is that, "they are excited at lower energy photon and in emission they are giving high energy photon". They absorbed the IR radiations and giving emission in the visible and UV region.