Effects of high pulse intensity and chirp in two-dimensional electronic spectroscopy of an atomic vapor

Abstract

The effects of high pulse intensity and chirp on two-dimensional electronic spectroscopy signals are experimentally investigated in the highly non-perturbative regime using atomic rubidium vapor as clean model system. Data analysis is performed based on higher-order Feynman diagrams and non-perturbative numerical simulations of the system response. It is shown that higher-order contributions may lead to a fundamental change of the static appearance and beating-maps of the 2D spectra and that chirped pulses enhance or suppress distinct higher-order pathways. We further give an estimate of the threshold intensity beyond which the high-intensity effects become visible for the system under consideration.

Theory of multiple quantum coherence signals in dilute thermal gases

“…Before we proceed, let us notice that, so far, we described the action of the laser pulses on the atoms non-perturbatively in the pulse area ϑ. Strong pulses (e.g., ϑ ≈ π) induce a nonlinear response of the atoms [19,53] and can be used as a control and diagnostic tool in electronic spectroscopy [54,55]. Furthermore, we have shown that strong pulses substantially modify the MQC signals [42].…”

Equation-of-Motion Methods for the Calculation of Femtosecond Time-Resolved 4-Wave-Mixing and N-Wave-Mixing Signals

“…Typically, weak-field signals are measured; that is, in 2WM, 4WM, or 6WM experiments each pulse interacts with the system only once. 95,96,588,658−660 Population-detected signals of atomic 493 and molecular 661−663 systems have also been measured in the strong-field regime.…”

“…A number of femtosecond 4WM experiments revealed that richer information on the photoinduced dynamics in atomic vapors, − polyatomic chromophores, − multichromophore aggregates, − and nanosystems − can be obtained by applying more intense laser pulses (see refs − for reviews). On the theoretical side, a variety of simulations of 4WM signals beyond the limit of weak system–field coupling have been reported. ,,,,− Single-molecule femtosecond spectroscopy of individual chromophores − and antenna complexes , also usually requires strong pulses.…”

“…The action-detection of signals is a current trend in femtosecond spectroscopy. The signals can be measured through the detection of incoherent responses such as the total fluorescence, − ,,,,− the photocurrent, − or the mass spectra. − The time-dependence of these signals is determined by the time delays between the laser pulses. Typically, weak-field signals are measured; that is, in 2WM, 4WM, or 6WM experiments each pulse interacts with the system only once. ,,,− Population-detected signals of atomic and molecular − systems have also been measured in the strong-field regime.…”

Optical Two-Dimensional Coherent Spectroscopy of Cold Atoms

“…Originated in nuclear magnetic resonance [5], the concept of multi-dimensional Fourier-transform spectroscopy has been implemented in the optical region using femtosecond lasers and developed into a powerful tool to study energy level structures, couplings, and dynamics in a variety of complex systems such as proteins [6], photosynthetic systems [7,8], semiconductor quantum wells [9][10][11][12][13], quantum dots [14][15][16][17], 2D mate-rials [18,19], perovskites [20,21], atomic vapors [22][23][24][25][26][27][28][29][30][31][32][33][34][35], and weakly-bound molecules on helium nanodroplets in a molecular beam [36]. Particularly, double-quantum 2DCS provids an extremely sensitive background-free detection of dipole-dipole interactions in both potassium (K) [25,30] and rubidium (Rb) [27,30] atomic vapors.…”