Sm³⁺ as effective deactivator for enhanced ∼3 μm laser emission in Er,Sm:SrLaAlO₄ crystal

A promising mid-infrared (MIR) laser crystal with Er, Sm co-doped SrLaAlO₄ (Er,Sm:SLA) crystal was successfully grown using the Czochralski (CZ) method. It was the first time that co-doped Sm³⁺ ion as deactivator for Er³⁺ activated ∼ 3.0 μm laser. The crystal structure, absorption spectra, emission spectra, and energy level lifetime were discussed in detail. The band structure and density of states were calculated by the density functional theory. The spectral parameters were calculated using Judd-Ofelt (J-O) theory and the deactivate effect of Sm³⁺ was systematically studied. The introduction of Sm³⁺ ions enhance the 2.7 µm mid infrared emission intensity by three times, and decrease the lifetime of ⁴I_13/2 energy level of Er³⁺ ion from 4.35 ms to 0.98 ms. The lifetime ratio of upper and lower levels for 2.7 µm emission was calculated to be 0.63, which is 2.6 times of Er:SLA crystal and comparable to some commercial crystals. All the results indicate that the Sm³⁺ ion is an effective deactivator for ∼3 μm laser emission. The long upper level lifetime, as well as the large lifetime ratio, the broadening spectra characteristics and the appropriate emission cross-section show the Er,Sm:SLA crystal a good gain material for ultrafast and tunable lasers at ∼3.0 μm.