Optical characterizations of Er3+-doped KLa(PO3)4 phosphate crystals

Abstract Absorption spectra were recorded for the three samples of KLa 1− x Er x (PO 3 ) 4 crystal, where x = 0.025, 0.05 and 1, at room temperature in the 400–900 nm spectral range. Fluorescent emissions from the 4 S 3/2 and 4 F 9/2 multiplets were observed under pulsed laser excitation in the 2 H 11/2 multiplet ( λ exc = 532 nm ) and in the 4 G 9/2 multiplet (355 nm). The time-resolved luminescence of these emissions has also been studied. The decays are shown to be exponential, with decay times on the order of 1 μs, independently of the erbium content. No significant lengthening of the decay time is observed as erbium concentration decreases from 100 to 2.5 at.%. Non-radiative relaxations related to multiphonon emission have been evoked to be at the origin of the excited state depopulation in the Er 3+ -doped KLa(PO 3 ) 4 crystals studied. The emission spectra of the lasing transition 4 I 13/2 → 4 I 15/2 in Er 3+ -doped KLa(PO 3 ) 4 phosphate crystals have also been analyzed. The influence of the erbium concentration on this electronic transition has been discussed as well. It was observed that the increase of Er 3+ ion concentration, in the 2.5–100 at.% range, results in a spectral broadening of the 1.54 μm emission band. Reabsorption has been evoked as the main mechanism to explain the broadening of the 4 I 13/2 → 4 I 15/2 emission line.