Four-wave mixing at maximum coherence and eliminated Doppler broadening   controlled with the driving fields
  New feasibity of coherent quantum control of four-wave mixing processes in a resonant Doppler-broadened medium are studied. We propose a technique which enables one to enhance the quantum efficiency of nonlinear optical conversion. At the same time, it allows one to decrease the required intensities of the fundamental beams compared to those necessary in the approach based on coherent population trapping. The major outcomes of the analysis are illustrated with numerical simulation addressed within a practical medium. 
A. K. Popov and Alexander S. Bayev (Institute for Physics, Russian   Academy of Sciences, Krasnoyarsk, Russia), Thomas F. Ge...