QUANTUM INTERFERENCE IN RESONANCE FLUORESCENCE FOR A DRIVEN V-ATOM

We investigate the effect of quantum interference between the two tran sition pathways from the excited doublet to the ground level of a driv en V atom on the spectral features of the resonance fluorescence emiss ion. The ultranarrow spectral line at line center, which arises due to quantum interference, occurs over a wide range of parameters. The sma ller the ratio of the excited doublet splitting to the effective Rabi frequency, the more pronounced the spectral line narrowing. However, t he fluorescence emission is completely quenched when the atomic dipole moments are exactly parallel and the driving field is tuned to the av erage frequency of the atomic transitions. The narrow line is due to t he slow decay rate of one dressed state, while the quenching arises fr om dressed-state trapping. A finite laser linewidth destroys the spect ral narrowing features and the fluorescence quenching.