Transient-absorption phases with strong probe and pump pulses

Abstract

The quantum dynamics of a system of Rb atoms, modeled by a V -type three-level system interacting with intense probe and pump pulses, are studied. The time-delay-dependent transient-absorption spectrum of an intense probe pulse is thus predicted, when this is preceded or followed by a strong pump pulse. Numerical results are interpreted in terms of an analytical model, which allows us to quantify the oscillating features of the resulting transient-absorption spectra in terms of the atomic populations and phases generated by the intense pulses. Strong-field-induced phases and their influence on the resulting transient-absorption spectra are thereby investigated for different values of pump and probe intensities and frequencies, focusing on the atomic properties which are encoded in the absorption line shapes for positive and negative time delays.

Light-induced states in the transient-absorption spectrum of a periodically pumped strong-field-excited system

“…The spectrum thus results from the dynamics of the system only for t > τ , with the periodic sequence of pump pulses determining the state of the system encountered by the probe pulse at τ − . This is a typical feature of the spectra in a pump-probe setup for a noncollinear geometry, which was already recognized for the single-pumppulse case [23,24]. In contrast to the probe-pump case, where the periodic excitation of the system following the probe pulse causes the appearance of LISs, here the train of pulses preceding the probe pulse only determines the state in which the system is prepared.…”

“…When τ < 0, the probe pulse completely precedes the sequence of pump pulses, while it fully follows the train of pump pulses when τ > (N − 1)T p . The general structure of the absorption spectrum for these two experimental setups was previously investigated for a single pump pulse [21,23], also in the presence of an intense probe pulse [24]. In the following, we will show how the formulas presented therein can be modified in order to account for a sequence of pump pulses, and how this is imprinted in the shape of the absorption spectra for increasing values of N .…”

“…In transient-absorption spectroscopy experiments, this geometry is employed to measure the spectrum of the probe pulse independent of the pump pulse, and thus separate the contributions from pulses with the same laser frequency. In this geometry, however, fast oscillations of the absorption spectrum as a function of time delay are effectively averaged out in an experiment [21,24]. We will account for this by identifying and selectively removing fast time-delay-dependent oscillating terms in the resulting single-particle absorption spectra S(ω, τ ):…”

“…If the duration of the probe pulse is comparable with that of the pump pulse, the absorption spectra do not provide the resolution necessary to access the real-time dynamics taking place during the pump pulse. This is for example the case when optical transitions have to be studied or controlled with optical femtosecond pump and probe pulses of equal duration [21][22][23][24]. The Rabi oscillations responsible for the appearance of LISs take place only within the pump pulse, and a probe pulse of equal duration does not have the required resolution to distinguish them.…”

Laser-Induced Control of the Optical Response of Aluminum Phthalocyanine Chloride Complexes Dissolved in Ethanol

“…To mimic the non-collinear experimental setup, an additional wave-front averaging { Refs. [43,44]} is performed by calculating the absorption spectra with different carrier-envelope-phase (CEP) values for the control pulse, while keeping the CEP of the excitation pulse fixed, and subsequently taking the average of the resulting absorption spectra. Using this procedure the optical interference (heterodyne effect) between both optical pulses is suppressed in the toy model.…”