Er3+ concentration-dependent microstructural and upconversion luminescence process of transparent perfluoride composite glass

Er 3+ -doped transparent perfluoride composite glass (PFCG) containing SrF 2 crystals was obtained by a one-step method. PFCG was observed to maintain the formation of a single SrF 2 crystal phase even when the Er 3+ doping concentration was as high as 8 mol%. Importantly, Er 3+ was enriched in the crystalline region, which promoted grain growth. This ensures effective emission of upconversion (UC). Interestingly, green and red UC emissions were found to be tunable in the range of 1–6 mol% Er 3+ doping, and the UC emission and lifetime started to produce concentration quenching until 6 mol% Er 3+ doping. To the best of our knowledge, this is the highest quenching concentration of Er 3+ in composite-glass materials. Moreover, the dominant UC process was systematically analyzed at different doping levels. This research is expected to provide ideal candidate materials and appropriate Er 3+ concentration doping level guidance in PFCG for the field of UC lasers.