Mechanisms of up-conversion excitation of blue emission in YAG:Tm, Yb A. KNÜPFER, V. OSTROUMOV, E. HEUMANN, G. HUBER et V. LUPEI J. Phys. IV France, 04 C4 (1994) C4-501-C4-504 DOI: 10.1051/jp4:19944120