De-excitation mechanisms of BaLiF 3:Co 2+ crystals

Abstract

The de-excitation mechanisms from the 4 T 2( 4 F) level for a promising new vibronic laser material, BaLiF 3:Co 2+ (emission centered at 1588 nm, FWHM=426 nm), are reported. At low temperatures, the decay time is on average equal to 580 μs, decreasing very rapidly above 80 K ( τ RT=1 μs). This decrease is due to multiphonon processes from the excited vibronic level 4 T 2( 4 F) to the highly excited vibronic fundamental level 4 T 1( 4 F) promoted by the vibrational modes E g and T 2g of the BaLiF 3 crystal. The decay time dependence on the temperature was fitted according to the Mott–Seitz model, presenting a good agreement. The following parameters were determined: radiative lifetime, τ R=580 μs, nonradiative lifetime, τ NR=0.17 μs and activation energy, Δ E=587 cm −1.