Managing optical heating via Al³⁺-doping in Er³⁺:SrF₂ powder phosphors prepared by combustion synthesis

Quenching of photoluminescence due to optical heating generated by high power laser sources has been identified as a major concern for photonics applications that relies on inorganic phosphor materials. Here we investigate how erbium-doped strontium fluoride (Er3+:SrF2) powders prepared by combustion synthesis respond to intense optical heating. We found that the near-infrared to visible photon up-conversion (UC) luminescence from Er3+ was quenched and the internal temperature of the sample increased from 298 to 695 K when the excitation power of a CW diode laser operating at 808 nm was increased from 0.1 to 2.1 W. However, when SrF2 was co-doped with Al3+, we observed an increase in the UC intensity and an unexpected internal temperature reduction of up to 155 K for an excitation power of 2.1 W. Our analysis suggests that Al3+ decreases the phonon energy and increases the local symmetry of the environment of the rare-earth ion in SrF2.