Breakage of Yb3+ pairs by Na+ in Yb3+-doped CaF2 laser host S. Hraiech, A. Jouini, K. Jin Kim, Y. Guyot, C. Goutaudier, A. Yoshikawa, M. Trabelsi-Ayadi and G. Boulon Ann. Phys. Fr., 32 2-3 (2007) 59-61 Published online: 23 May 2008 DOI: 10.1051/anphys:2008007