Erbium spectroscopy and 1.5-μm emission in KGd(WO4)2: Er,Yb single crystals

We grew good-optical-quality KGd(WO₄)₂ single crystals doped with erbium and ytterbium ions at several concentrations of dopants using the top-seeded-solution growth slow-cooling method (TSSG). We performed the spectroscopic characterization of this material related to the 1.5-mm infrared emission of erbium which is interesting for laser applications. To do this, we carried out polarized optical absorption at room temperature (RT) and at low temperature (6 K) and performed luminescence studies of the emission and lifetime. We obtained the 1.5-mm emission of erbium after selective laser pump excitation of the ytterbium ion and energy transfer between the two ions. The maximum emission cross section for 1.5 mm was about 2.56×10^-20 cm² for the polarization of light with the electric field parallel to the N_m principal optical direction. This value was higher than for other erbium-doped materials with application in solid-state lasers such as LiYF₄:Er(YLF:Er), Y₃Al₅O₁₂:Er(YAG:Er), YAlO₃:Er, and Al₂O₃:Er.