Different processes responsible for blue pumped, ultraviolet and violet luminescence in high-concentrated Er3+:YAG and low-concentrated Er3+:YAP crystals

Ultraviolet and violet upconverted luminescence in high-concentrated (8.4 at%) Er3+:YAG and low-concentrated (1 at%) Er3+:YAP crystals has been investigated under blue laser excitation of the 4F7/2 multiplet. The upconversion mechanisms were studied in detail based on upconversion luminescence intensity dependence and decay curves. Upconversion luminescence was attributed to energy transfer processes in Er3+:YAG and excited state absorption processes in Er3+:YAP, respectively.