The optical spectroscopy of LiGa5O8: Ni2+

The optical spectroscopy of nickel-doped LiGa5O8 is presented. Absorption and luminescence measurements taken over a wide temperature range indicate that the dopant nickel ion is doubly charged and occupies a site of near-octahedral symmetry. We observe a luminescence transition in the near-infrared which is assigned to the 3T2(3F)→3A2(3F) transition of the Ni2+ ions. No visible luminescence is observed. Luminescence decay times as a function of temperature have been measured to determine the presence and extent of nonradiative transitions in this system. The near-infrared luminescence appears to have a high quantum efficiency up to temperatures of around 350 K above which nonradiative processes occur. The high quantum efficiency and broad smooth shape of the luminescence makes this an interesting transition from the viewpoint of tunable laser action.