Phonon coupling of Cr^3^+ ions in Cs_2NaAlF_6 crystals.

Abstract

We have studied the influence of the electron-lattice coupling on the luminescence quantum yield for Cr^3^+ ions in a Cs_2NaAlF_6 crystal. For this purpose, we analyze the absorption and emission spectra of Cr^3^+ ions by means of the configurational coordinate model in the harmonic approximation. We have found the energy of the breathing phonon associated to Cr^3^+ ions in this host. In our findings we explain the high value of luminescence quantum yield reported previously (near to 70%), if we take into account the uncoupling between the breathing phonon and the normal modes associated to the bulk vibration. The Cr^3^+:Cs_2NaAlF_6 crystals promise to be a potential efficiency tunable laser device in the near infrared (700–900 nm) spectral range.