| Fundamental aspects and potential application of the one vs. two-photon absorption coherent control scenario are investigated. In this scenario, fields with frequency components o and 2o are employed to generate phase-controllable net dipoles or currents in spatially symmetric systems (symmetry breaking).;First, the scenario is shown to have a classical analogue and the quantum-to-classical transition of the symmetry breaking effect is studied. For this, a time-dependent perturbative calculation, that admits an analytical classical limit, is carried out for a quartic oscillator in the Heisenberg picture. The laser-induced interferences responsible for the effect are shown to survive in the classical limit and to be the origin of classical control. Further, minimum requirements for the appearance of the effect in both quantum and classical systems are isolated and shown to be identical: anharmonicities in the system's potential and a driving field with a low temporal symmetry.;Next, the ability of the scenario to induce electronic transport along conjugated polymers and molecular wires is investigated. For this, the photoindcued vibronic dynamics of trans-polyacetylene oligomers, isolated or coupled to metallic leads, is followed in a mixed quantum classical approximation. It is shown that the vibronic couplings have deleterious effects on the control since they introduce ultrafast electronic dephasing. Nevertheless, control is still viable, the most promising route involving the use of laser pulses with durations that are comparable to the electronic dephasing time.;Then, a novel way to induce ultrafast currents using o + 2o fields along molecular wires is demonstrated. The mechanism relies on Stark shifts, instead of photon absorption, to transfer population to the excited states and exploits the temporal profile of the field to generate rectification. Contrary to the case above, this mechanism is robust to vibronic couplings and offers almost complete control over the photoinduced currents.;Last, the analogy between coherent control scenarios and Young's double-slit experiment with matter is investigated, and shown to be flawed. Specifically, it is demonstrated that matter interference effects are not necessary for the emergence of laser control. The latter relies on the nonlinear response of matter to optical fields, and these processes have a clear classical manifestation. |
