STRONG-FIELD COHERENT CONTROL

In the following, we will discuss two basic - and in a sense complementary [44] - physical mechanisms to exert efficient control on the strong-field-induced coherent electron dynamics. In the first scenario, SPODS is implemented by a sequence of ultrashort laser pulses (discrete temporal phase jumps), whereas the second scenario utilizes a single chirped pulse (continuous phase variations) to exert control on the dressed state populations. Both mechanisms have distinct properties with respect to multistate excitations such as those discussed in Section 6.3.3. 

We demonstrate coherent control in strong fields beyond (i) population control and (ii) spectral interference, since (i) control is achieved without altering the population during the second intense laser pulse, i.e., the population during the second laser pulse is frozen, and (ii) the quantum mechanical phase is controlled without changing the spectrum of the pulse sequence. The control mechanism relies on the interplay of the quantum mechanical phase set by the intensity of the first pulse and the phase of the second pulse determined by the time delay. 

In the present chapter, the rapidly growing subject of atoms in strong laser fields has been briefly described, the main emphasis being on the novel effects which have been observed. Several aspects of the problem have not been discussed for example, above 1020 Wcm-2, relativistic effects will become important, although these have not yet been observed. Similarly, we have omitted any discussion of coherent control in two-colour excitation and femtosecond chemistry. 

In K2 the electron dynamics is steered via the temporal phase of a femtosecond laser pulse resonant to the electronic transition and controllable with attosecond precision (see Fig. 8.10, inset). The underlying excitation scheme is the non-adiabatic SPODS mechanism [65,101], a strong-field resonant interaction in which the initial part of the laser pulse creates a coherent superposition between two electronic states inducing an oscillating charge distribution with maximum amplitude. After evolution on the coherently coupled PES, a later part of the laser pulse is timed... 

Bayer T, WoUenhaupt M, Baumert T (2008) Strong-field control Itmdscapes of coherent electronic excitation. J Phys B 41 074007... 

Coherent optimal control by tailored strong-field laser pulses... 

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