Identifying the orbital angular momentum of light based on atomic ensembles Liang Han, Mingtao Cao, Ruifeng Liu, Hao Liu, Wenge Guo, Dong Wei, Shaoyan Gao, Pei Zhang, Hong Gao and Fuli Li EPL, 99 3 (2012) 34003 Published online: 09 August 2012 DOI: 10.1209/0295-5075/99/34003