Soviet Journal of Quantum Electronics
Experimental observation of the nonadditivity of various mechanisms of population inversion of the4I11/2→4I13/2transition of the Er3+ion in a YSGG:Cr3+:Er3+crystal
Mikhail A. Noginov, G. K. Sarkisyan, Valerii A Smirnov, A F Umyskov, Ivan A Shcherbakov