Selective population of dressed state

WoUenhaupt M, PrSkelt A, Sarpe-Tudoran C, Liese D, Baumert T (2005) Strong field quantum control by selective population of dressed states. J Opt B 7 S270... 

State. The latter is verified by the population dynamics in frame (ii) around t = 0. Subsequently, the pulse continues to invert the bare state system, which is typical for RAP. Just like the ground state the excited p-state exhibits no permanent dipole moment. Therefore, both (/ )(t) and V) t) converge back to zero as the system is steered adiabatically toward state 2). This indicates the successive loss of selectivity among the dressed states, which is in fact observed in frame (ii) for f > 0. By the end of the pulse, both dressed states are again fully equalized. 

Figure 6.10 Ultrafast efficient switching in the five-state system via SPODS based on multipulse sequences from sinusoidal phase modulation (PL). The shaped laser pulse shown in (a) results from complete forward design of the control field. Frame (b) shows die induced bare state population dynamics. After preparation of the resonant subsystem in a state of maximum electronic coherence by the pre-pulse, the optical phase jump of = —7r/2 shifts die main pulse in-phase with the induced charge oscillation. Therefore, the interaction energy is minimized, resulting in the selective population of the lower dressed state /), as seen in the dressed state population dynamics in (d) around t = —50 fs. Due to the efficient energy splitting of the dressed states, induced in the resonant subsystem by the main pulse, the lower dressed state is shifted into resonance widi die lower target state 3) (see frame (c) around t = 0). As a result, 100% of the population is transferred nonadiabatically to this particular target state, which is selectively populated by the end of the pulse.

In order to switch the system into the upper target state 5) merely the sine-phase 0 has to be varied by half an optical cycle, that is, by A(p = n. In this case, the main pulse is phase-shifted by Af = -l- r/2 with respect to the pre-pulse and couples in antiphase to the induced charge oscillation. Hence, the interaction energy is maximized and the upper dressed state u) is populated selectively. Due to the energy increase, the system rapidly approaches the upper target state 5). The ensuing nonadiabatic transitions between the dressed states u) and 1 5) result in a complete population transfer from the resonant subsystem to the upper target state, which is selectively excited by the end of the pulse. 

Figure 6.14 Evolution of the photoelectron spectra during the adaptive optimization of the fast versus the slow photoelectrons. The fitness function is defined as / = 5F — S, where F denotes the area of the fast photoelectrons (gray shaded) and S the area of slow photoelectrons. The number of iterations increases from (a) to (d). The horizontal lines indicate die reference intensities of die slow (dashed) and fast (bold) photoelectrons at die beginning of die optimization procedure. The optimal pulse (d) realizes die population of die upper dressed state during ionization with supreme selectivity.

Fig. 8.10 SPODS scheme of K2. A sketch of the SPODS pulse sequence is shown in the inset. The first subpulse creates a superposition between the X Sg and A S + states (gray dash-dotted arrow). During the second pulse the X — A subsystem is photon locked. The optical phase controls which of the dressed states (indicated as black dotted lines) energetically separated by is selectively populated. Absorption of another photon leads to population transfer to either the lower target states, represented by the 4 Sg" " (gray dotted arrow) or to the upper target states, represented by the 5 (black dashed arrow)...

The experiment was based on theoretical predictions that LICS can give rise to channel selectivity [245-247]. In these works it was shown that the dressing of a continuum with an initially unpopulated bound state by a laser of frequency coi, performed while exciting a populated bound state to the same dressed continuum using a laser field of frequency twi, resulfs in a quantum interference whose (desfructive or consfruefive) charaefer depends on the final channel. An illusfration of this scenario is shown in the left panel of Figure 3.18. 

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