Spontaneous emission phase control

The effect of quantum interference on spontaneous emission in atomic and molecular systems is the generation of superposition states that can be manipulated, to reduce the interaction with the environment, by adjusting the polarizations of the transition dipole moments, or the amplitudes and phases of the external driving fields. With a suitable choice of parameters, the superposition states can decay with controlled and significantly reduced rates. This modification can lead to subnatural linewidths in the fluorescence and absorption spectra [5,10]. Furthermore, as will be shown in this review, the superposition states can even be decoupled from the environment and the population can be trapped in these states without decaying to the lower levels. These states, known as dark or trapped states, were predicted in many configurations of multilevel systems [11], as well as in multiatom systems [12],... 

Spontaneous emission in a multilevel atom can be controlled by changing not only the mutual orientation of the dipole moments of two interfering transitions but also the phase difference of driving lasers used for the excitation of the... 

Our review of the phase control of spontaneous emission will concentrate on the example of a V-type atom with nondegenerate transitions and nonorthogonal dipole moments driven by two laser fields. The lasers can have equal or different frequencies and each laser can couple to only one or both atomic transitions. 

E. Paspalakis, P.L. Knight, Phase control of spontaneous emission, Phys. Rev. Lett. 81... 

It is important to note at this point that, in the gas phase, the processes that destroy or scramble coherence, such as collisions or spontaneous emission, generally take place on a much longer time-scale than the process that is being coherently controlled by the shaped femtosecond laser field, and thus do not interfere. 

---