Probe gain with population inversion in a four-level atomic system with vacuum-induced coherence.
For a four-level atomic system with a doublet of closely spaced levels, we find that, owing to the coherence that results from the vacuum of the radiation field, population trapping at excited levels and probe gain with population inversion can be achieved with weak incoherent pumping. This gain is different from both the conventional lasing gain and gain without inversion in that there exists population inversion on probe transitions but the inversion is achieved by the vacuum-induced coherence.
Wu
Jin-Hui
JH
College of Physics, Jilin University, Changchun 130023, China. wujinhui0431@sina.com
Zhang
Hui-Fang
HF
Gao
Jin-Yue
JY