Spectroscopic investigations of highly doped Er³⁺ : GGG and Er³⁺/Pr³⁺ : GGG crystals

Abstract

Heavily Er3+-doped and Er3+/Pr3+ co-doped Gd3Ga5O12 (abbreviated as Er : GGG and Er,Pr : GGG, respectively) laser crystals were synthesized by the Czochralski method. The synthesized laser crystals were characterized by absorption, up-conversion fluorescence, near-infrared (NIR) and mid-infrared (Mid-IR) fluorescence, and luminescence decay measurements. The optical parameters related to absorption and emission cross-sections and fluorescence lifetimes were evaluated and compared. It was found that the up-conversion and NIR fluorescence weaken, at the same time Mid-IR fluorescence intensity strengthens with the increment of Er dopant concentration or co-doping with Pr3+ in Er : GGG crystals. Furthermore, the self-termination bottleneck was broken successfully in the Er,Pr : GGG crystal, and the energy transfer efficiencies of Er3+ : 4I11/2 → Pr3+ : 1G4 and Er3+ : 4I13/2 → Pr3+ : 3F4 were determined.