Excited state absorption and energy transfer in the infrared laser material MgF2: Ni2+

Abstract

Infrared laser action and tunability of the solid state vibronic system MgF₂: Ni^{2 +} is obtained by pumping with the 7525 Å radiation of a c.w. krypton laser. Limitations to laser efficiency are attributed mainly to internal losses caused by excited state absorption and energy transfer phenomena. These phenomena are analysed and interpreted using data provided by absorption and fluorescence (decay and intensity) measurements in the infrared and visible regions. The energy transfer process is discussed in terms of the Dexter and Inokuti-Hirayama theories. The dominant inter-ion interaction is then attributed to the exchange mechanism, and a critical ion concentration for energy transfer of about 0·25% Ni²⁺ is deduced. This shows in turn that the laser efficiency of MgF₂: Ni²⁺, when it is pumped by a krypton laser, could be improved by using samples with lower concentrations.