Optical properties of Er3+-Yb3+ codoped Cd.7Sr.3F2 mixed single crystals

Absorption, excitation, fluorescence and decay spectra are carried out at room temperature on Er3+ (1%), Yb3+ (4%): Cd.7Sr.3F2 mixed single crystals. These crystals, with a good optical quality, are grown by the standard Bridgman method. This work concerns mainly the spectroscopic properties of the Er3+ ions incorporated in a fluorite-type crystal. Using the room temperature absorption spectra, the standard Judd-Ofelt (JO) model is applied to absorption intensities of Er3+ to obtain the three phenomenological intensity parameters by the least square fit procedure. The values obtained are in accordance with those of other fluoride hosts with good root mean square fitting. Compared to oxide materials, fluoride materials have, in general, low values ​​of Ω2. The low value of Ω2 is correlated to the cubic nature of the site occupied by the rare earth in the host matrix. These JO intensity parameters are then applied to determine the radiative transition probabilities (AJJ′), radiative lifetimes (τrad) and branching ratios (βJJ′) of Er3+ transitions. The green emission generated by the Er3+ ions directly excited in UV level, consisting in three well-resolved major lines, is more intense than the one. We have measured the fluorescence lifetime, the cross-section emission, the gain and the radiative quantum efficiency for both green and red band emissions. The obtained results are in good agreement with those of other fluoride laser crystals. From, the obtained spectroscopic data we suggest that Cd.7Sr.3F2 may offer green and red visible laser emission when doped with Er3+ ions.