Growth and investigation of optical properties and laser oscillations from ternary thiogallate crystals with laser active dopants

A wide range of rare earth doped crystals used as a lasing media includes: Y₃Al₅O₁₂ (YAG); Al₂O₃ (sapphire); chalcogenides of ZnS, ZnSe; sesquioxides of Y₂O₃, Sc₂O₃ and others. Ternary thiogallate compounds with common formula A^IIB₂³C₄ ⁶ (where A is: Ca, Sr, Ba; B is: Ga, Al; C is- S, Se, Te) consider as a perspective class of chalcogenide semiconductors revealing bright luminescence and laser oscillation properties when doped with rare-earth elements (Eu²⁺, Nd³⁺ , Ce³⁺ etc). In the present research, optical properties and observed laser oscillation of transparent ternary chalcogenide crystals of CaGa₂S₄ and CaGa₂Se₄ grown by the chemical vapor transport reaction and doped with Eu²⁺ (1.0-5.0 a t%) are described. The first observation of laser oscillation from a single crystal CaGa₂S₄ : Eu²⁺ (1.0-5.0 at%) have been reported earlier, and for CaGa₂Se₄ : Eu²⁺ it is reported for the first time in the present article. The life time of the excited state 4f⁶5d of Eu²⁺ ions in both crystals determined from the luminescence decay kinetics was ~3.8 μsec. It is shown that photoluminescence maximum in both crystals CaGa₂S₄ : Eu²⁺ and CaGa₂Se₄ : Eu²⁺ is due to the intra shell transition 4f⁶5d – 4f⁷(⁸S_7/2) ions.