High and uniform coherence creation in Doppler broadened double   lambda-like atomic system by a train of femtosecond optical pulses
  We present a detailed analysis of coherence creation in a four level double lambda-like atomic system using a train of ultra-short few-cycle Gaussian pulses. The effect of the Doppler broadening has been analyzed. It is possible to create high coherence across all the velocity groups in the atomic ensemble using pulses with low repetition frequency. The accumulation of coherence at different radial locations within the atomic beam cross-section as a function of the number of pulses in the train is also reported. We find that pulse train with lower repetition frequencies are able to generate high and nearly uniform coherence in a substantial part of the atomic system. 
Amarendra K. Sarma and Pawan Kumar
quant-ph physics.atom-ph physics.optics