Study of lasing threshold and efficiency in laser crystal powders B. García-Ramiro, I. Aramburu, M. A. Illarramendi, J. Fernández and R. Balda Eur. Phys. J. D, 52 1-3 (2009) 195-198 Published online: 24 January 2009 DOI: 10.1140/epjd/e2008-00245-5