Silicate Phosphors BaGa2Si2O8:Ln3+ (Er3+, Ho3+, Yb3+) Equipped with Intrinsic Optical Bistability toward Photonic Barcodes

Optical bistability phenomenon is of vital significance for technological applications such as optical telecommunications. Herein, novel upconversion (UC) luminescence phosphors, Ln3+ (Er3+, Ho3+)/Yb3+ co-doped BaGa2Si2O8, were developed. Irradiated by 980 nm laser, the system showed intrinsic optical bistability (IOB) and two different optical responses were observed under the same incident pump power, signifying that these phosphors can play a role in optical switching devices. This nonlinear phenomenon mainly originated from the appearance of large amounts of Yb3+–Yb3+ dimers in the title materials where the Yb3+ ions kept a higher density compared with the activators. In addition, the compounds displayed excellent temperature sensing performance and controllable spectrum modulation behavior, and photonic barcodes with reliable security and simple fabrication were designed for anti-counterfeiting based on the latter. This work not only offers useful enlightenment for the development and application of phosphors but also enables a deep understanding of IOB in lanthanide-doped materials.