Strong-field index enhancement via incoherent excitation

Abstract

We show that it is possible, in principle, to employ an incoherent field as a control fieldto achieve maximal atomic coherence for a probe field, which characterizes ultralargeindex of refraction and vanishing absorption. For this purpose we consider a three-levelVsystem in which there are two dipole transitions, of which one is weak and theother is strong. The strong probe field is applied to the weak transition and theincoherent field drives the strong transition. For such an arrangement, selectivedressed-population trapping, which corresponds to maximal atomic coherence, isestablished by relying on the incoherent field and the spontaneous relaxation totransfer population from one dressed state to the other. This scheme as anextreme example explains that strong-field index enhancement based on selectivedressed-population trapping is resistant to the control field fluctuations.