Stochastic Theory of Emission Spectrum from Strongly Driven System

The effect of frequency modulation on optical phenomena is reduced critically when the Rabi frequency increases beyond the inverse correlation time or the amplitude of the frequency modulation. This is observed in the time region as the change of the free induction decay rate from the Bloch type into the Redfield one. That is shown in this paper to be observable also in the frequency region as the narrowing of the central line and the side bands split-off by the Rabi frequency above and below it in the emission spectrum beyond the Rabi frequency equal to the inverse correlation time.