Study on Spectral Properties and Mid-Infrared Laser Performance of Er, La:CaF2 Crystals

Er3+-doped fluorite crystals, including CaF2 and SrF2, are considered as attractive laser gain materials in the mid-infrared (MIR) region with merits of high laser efficiency as well as low doping concentration. In this work, a series of Er, La:CaF2 crystals were grown and the modulation effect of co-doping La3+ ions on the spectral properties and mid-infrared laser performance was investigated. It was found that introducing La3+ ions can effectively manipulate the coordination environment of Er3+ ions embedded in CaF2 crystal, thus modulating the shape and intensity of absorption and emission bands. On the other hand, La3+ ions can partially substitute Er3+ sites in the clusters to form mixed clusters, which affects the energy transfer processes between Er3+ ions as well as ~3 μm laser performance, which is dominated by energy transfer up-conversion (ETU) processes between Er3+ ions. By co-doping La3+ ions into Er:CaF2 crystal at an appropriate concentration, the spectral parameter modulation can be achieved while maintaining a high MIR laser efficiency.