Ultraviolet upconversion in Pr3+:Y2SiO5 crystal by Ar+ laser (488 nm) excitationC. L. Sun, J. F. Li, C. H. Hu, H. M. Jiang and Z. K. JiangEur. Phys. J. D, 39 2 (2006) 303-306DOI: https://doi.org/10.1140/epjd/e2006-00102-7