Autler-Townes

Figure 9.7 A ground state j) is excited by a weak laser pulse e, to a resonance state q) belonging to a space Q decaying radiatively or nonradiatively to a space P. The q) state is coupled optically to a third state ) by strong guiding field 2 and undergoes as a result Autler-Townes splitting. As a...

Apparently, the time evolution of the IEq) component of 2i(t)) is governed by a quasi-energy of Eq - Q2(0I> whereas the time evolution of the I q) component of U2(0) is governed by a quasi-energy of + f22(0l- hi such a case, one says that the two levels are Autler-Towns split by an amount equal to 2 i22(0l ... 

The result is shown as the dot-dash curve of Figure 9.11. It is shown that the spontaneous emission has been effectively suppressed, with the suppression becoming more effective, the smaller is the Autler-Townes splitting A due to the CW laser. Also shown in Figure 9.11 (as the dashed line) are the natural decay curves, arising when we start with one of the eigenstates. As can be seen, this decay, which is nonexponential due to the interaction between the resonances, is still much faster than the suppressed decay aided by the interruptions. 

Figure 9.11 Suppression of the 2P-1S spontaneous emission in the hydrogen atom, for which the natural linewidth is 1.66 X 10 cm". The solid lines display the decay of the optimized superposition of the Autler-Townes split levels with no interruptions. The dot-dashed lines are the decay curves of the same superposition states in the presence of interruptions. The dashed lines display the average decay of the two Autler-Townes split components. The optimization time t (marked by a triangle) is 0.2/T(= 0.65 ns), and the total time range displayed is up to 3/r(= 10 ns). A is the Autler-Townes splitting induced by the CW laser and T denotes the natural linewidth. Reprinted figure by permission from Ref. [38]. Copyright 2003 by the American Physical Society.

In this contribution recent results [13] on the control of the quantum mechanical phase of an atomic state in strong laser fields studied using the Autler-Townes (AT) effect [14] in the photoionization of the K (4p) state are discussed. We demonstrate quantum control beyond (i) population control and (ii) spectral interference, (i) We show, that for suitable combinations of the laser intensity of the first pulse and the time delay the second resonant intense laser pulse leaves the excited state population unchanged. However, the knowledge of the... 

In Figure 9.7 we illustrate the formation of the analogous EIT dark state, as described by Eq. (9.59), as a function of time. We see that when the pulse is weak (t = 1.7) the (Autler-Townes) splitting between the two field-dressed states is small and the EIT dark state resembles a very narrow hole. As the pulse gets... 

Fig. 9.7 Formation of the EIT hole as a result of an Autler-Townes splitting of a resonance according to Eq. (9.59). Shown is the line shape at three different times, at the peak of the pulse t — 0, as the pulse begins to wane, t = 0.85, and at the tail of the pulse, t = 1.7. A simple Gaussian pulse of the form 2(0 = n exp(—t2) was assumed.

INVESTIGATION OF AUTLER-TOWNES EFFECT IN SODIUM DIMERS... 

Abstract Experiments under way will provide high-resolution studies of the Autler-Townes... 

Keywords Autler-Townes effect, dynamic Stark shift, molecular spectra... 

Investigation of Autler-Townes effect in sodium dimers... 

As can be seen, the observations of Fig. 3 fit the pattern of a well resolved Autler-Townes doublet. The separation of the two components is smallest when the detuning is smallest it then gives a direct measure of the Rabi frequency of the S-field transition. 

Consider the Menon-Agarwal approach to the Autler-Townes spectrum of a V-type three-level atom. The atom is composed of two excited states, 1) and 3), and the ground state 2) coupled by transition dipole moments with matrix elements p12 and p32, but with no dipole coupling between the excited states. The excited states are separated in frequency by A. The spontaneous emission rates from 1) and 3) to the ground state 2) are Tj and T2, respectively. The atom is driven by a strong laser field of the Rabi frequency il, coupled solely to the 1) —> 2) transition. This is a crucial assumption, which would be difficult to realize in practice since quantum interference requires almost parallel dipole moments. However, the difficulty can be overcome in atomic systems with specific selection rules for the transition dipole moments, or by applying fields with specific polarization properties [26]. 

Although all the examples chosen involve singlet states, for which the theory is especially simple, there is no problem in extending the method to more complex Zeeman patterns, or indeed in including the effect of Paschen-Back uncoupling on the MOV spectrum [166]. The influence of -mixing on MOV patterns has also been studied, and is in principle well understood [167], If the experiment is performed with lasers, the influence of laser power on Faraday rotation arises both by population transfer and by the Autler-Townes splitting (section 9.10) [173]. 

The two satellites on either side of the main transition are called an Autler-Townes doublet after the names of those who first observed them [473], They were, however, predicted at an earlier date by Mollow [474]. An elegant method of calculating the fluorescence profile was described by Cohen-Tannoudji and Avan [475]. A very full discussion of how to represent this problem, including the central elastic component, the inelastic contributions and the sidebands, can be found in lecture notes by Co hen-Tannoudji [476]... 

The previous few examples show that, under coherent illumination, one can no longer consider observed spectral intensities as purely characteristic of the atom, since the properties of the Autler-Townes doublet depend on the laser intensity, and the profile of a laser-excited autoionising line will in general possess a shape unrelated to that of an atom excited by a weak source. 

S. Menon, G. Agarwal, Gain components in the Autler-Townes doublet from quantum interferences in decay channels, Phys. Rev. A 61 (1999) 013807. 

Finally, Fig. 6 shows that measuring in this case the ratio between the lengthes of dark and bright periods gives the possibility to detect, on a single atom, the Autler-Townes effect induced on the weak red transition by the intense blue laser excitation. 

---