  Sub-Poissonian light generation in the non-degenerate three-wave mixing is
studied numerically and analytically within quantum and classical approaches.
Husimi Q-functions and their classical trajectory simulations are analysed to
reveal a special regime corresponding to the time-stable sub-Poissonian
photocount statistics of the sum-frequency mode. Conditions for observation of
this regime are discussed. Theoretical predictions of the Fano factor and
explanation of the extraordinary stabilization of the sub-Poissonian photocount
behavior are obtained analytically by applying the classical trajectories.
Scaling laws for the maximum sub-Poissonian behavior are found. Noise
suppression levels in the non-degenerate vs degenerate three-wave mixing are
discussed on different time scales compared to the revival times. It is shown
that the non-degenerate conversion offers much better stabilization of the
suppressed noise in comparison to that of degenerate process.
