Influence of looping mechanisms in up-conversion processes in Yb-Tm-Ho doped Gd3Ga5O12 A. BRENIER, C. GARAPON, C. MADEJ, C. PÉDRINI et G. BOULON J. Phys. IV France, 04 C4 (1994) C4-431-C4-434 DOI: 10.1051/jp4:19944103