SPONTANEOUS EMISSION OF A DRIVEN FOUR-LEVEL DOPPLER BROADENED SYSTEM

We have studied the steady spontaneous emission spectrum of a four-level Doppler-broadened system driven by three coherent fields. It is found that the fluorescence spectrum is composed of nine contributions. The spectral components have quite different widths and peak heights compared with the case of the standard driven two-level or three-level resonance fluorescence. We provide numerical results in support of our arguments for arbitrary values of the atomic and field parameters.