450 nm light-induced upconversion ultraviolet-C photons for optical information encryption and sterilization

Ultraviolet-C (UVC) photons play a key role in many fields such as covert communication, bacterial inactivation, information storage, and encryption. Because the UVC component of solar spectrum is almost absorbed by the ozone layer around our earth, there is little natural UVC light on the earth. Therefore, developing artificial UVC light source is of great significance. The visible-to-UVC upconversion mechanism has been demonstrated to be a useful strategy. Here, we introduce a visible-to-UVC upconversion system, that is, CaSrSiO4:Pr3+. Under excitation of both commonly used laser and light-emitting diode at 450 nm, CaSrSiO4:Pr3+ emits UVC photons. The presence of UVC light of CaSrSiO4:Pr3+ has also been confirmed by a solar blind camera, in addition to an optical spectrometer. Moreover, experimental results show that the UVC emission of CaSrSiO4:Pr3+ is assigned to a two-photon assisted upconversion mechanism. In the end, we demonstrate the potential applications of CaSrSiO4:Pr3+ for information encryption and sterilization.