Photon statistics of radiation in an incoherently pumped three-level   cascade system
  We study the intensity-intensity correlations of the radiation emitted on probe transition in a three level cascade electromagnetically induced transparency (EIT) scheme. By applying an incoherent pump, we also monitor further changes in the characteristics of the emitted radiation. It is found that application of even a very weak incoherent pump can significantly alter the characteristics of the emitted radiation, even though the EIT characteristics remain unaltered. Our study demonstrates that for certain range of parameter values, the two photon correlation function in the probe transition oscillates between classical and non-classical domains. 
Shaik Ahmed, Preethi N. Wasnik, Suneel Singh and P. Anantha Lakshmi
quant-ph physics.optics