  Using numerical simulations, we show that atomic high order harmonic
generation, HHG, with a circularly polarized laser field offers an ideal
framework for quantum-classical correspondence in strong field physics. With an
appropriate initialization of the system, corresponding to a superposition of
ground and excited state(s), simulated HHG spectra display a narrow strip of
strong harmonic radiation preceded by a gap of missing harmonics in the lower
part of the spectrum. In specific regions of the spectra, HHG tends to lock to
circularly polarized harmonic emission. All these properties are shown to be
closely related to a set of key classical periodic orbits that organize the
recollision dynamics in an intense, circularly polarized field.
