Observation of ESA, ET and thermally enhanced frequency upconversion in Nd3+: LiTeO2 glass K. Kumar, D. K. Rai and S. B. Rai Eur. Phys. J. Appl. Phys., 41 2 (2008) 143-149 Published online: 06 February 2008 DOI: 10.1051/epjap:2008008