Phase-Controlled Currents in Semiconductors

Second-Harmonic Generation Induced by Electric Currents in GaAs

“…Here N 2D is the areal carrier density. We note that although current injection by the coherent control technique has been demonstrated in many materials by steady-state electric measurement, terahertz detection, and spatially resolved pump-probe techniques, [11,19,20,[23][24][25] the current-induced SHG demonstrated here allows us to time-resolve the ultrafast dynamics of these currents.…”

An Approach To “Quantumness” In Coherent Control

“…For example, the path alternatives are given by the two excitation processes in a 1 vs. N coherent control scenario. The resultant CCI framework is general and applicable to many systems, from atoms [15,66] to molecules [27,45,[67][68][69] to bulk solids [4,5,20,30,[70][71][72][73][74][75]. Further, the control field can be in a semiclassical coherent or in a quantum state of light, such as a multimode Fock state or a squeezed state.…”

“…Equation (5) shows explicitly that the phases φ i affect the field terms, but not the response functions, which depend on the field frequencies, but not on the field phases φ i . This feature is common to both the classical and the quantum descriptions of conventional two-color weak-field control, and generalizes the case of the quartic oscillator [6] reviewed in Sec.…”

“…In particular, they rely on the functional form of this equation, which is reminiscent of double slit interference, the phase sensitivity of the control, and the display of nonadditivity of the contributions. Early two-color photoionization experiments with alkali atoms, [14,15,32,33], serve as seminal examples of this scenario, as do experiments on current directionality in quantum wells [5] and semiconductors [20]. However, phase sensitivity and nonadditivity can also be of classical origin arising, for example, in transport processes [34].…”

“…This particular control scenario has proven of interest in applications ranging from control of electric currents [4][5][6][7] to the control of laser phase envelopes in precision measurements [8,9], and is the primary scenario upon which we focus in this Advances. Two-color phase control has repeatedly [3,5, been explained as a quantum analog of Young's double slit experiment [31], with the slits replaced by two independent and mutually exclusive dynamical pathways, A and B, both leading from an initial material state |ψ(t = −∞) to a final state |ψ(t = ∞) . In this picture, path A is given by a 1-photon transition induced by the laser field of frequency N ω, and path B by an N -photon transition caused by the second field of frequency ω.…”