Spectroscopy of Kznf3:Co

Tunable laser action in the near infrared (1.9um) has been observed from Co2+ ions as impurities in perovskite-structure KZnF3The laser emission occurs between the Co2+-ion cubic-field 4T2(4F) excited state and the 4T1(4F) ground state. The electronic structure of these two terms has been studied as a function of the Co2+ion concentration using Raman scattering and infrared absorption and emission spectroscopy. The 4T 1and 4T 2energy levels of single Co2+ ions have been determined from measurement at low cobalt concentrations (less than 2 at.%), and the 4T 2term exhibits effects due to the dynamic Jahn-Teller interaction. The vibronic structure seen in infrared absorption has also been assigned. At higher Co2+ ion concentrations the spectra show additional features due to the presence of clusters of the magnetic ions (predominantly pairs for concentrations less than 15 at.%). A theoretical analysis of the pair spectrum allows the bare Co2+-Co2+ exchange interaction to be determined.