Ultrafast Mapping of Coherent Dynamics and Density Matrix Reconstruction in a Terahertz-Assisted Laser Field

Abstract

A time-resolved spectroscopic protocol exploiting terahertz-assisted photoionization is proposed to reconstruct transient density matrix. Population and coherence elements are effectively mapped onto spectrally separated peaks in photoionization spectra. The beatings of coherence dynamics can be temporally resolved beyond the pulse duration, and the relative phase between involved states is directly readable from the oscillatory spectral distribution. As demonstrated by a photoexcited multilevel open quantum system, the method shows potential applications for subfemtosecond time-resolved measurements of coherent dynamics with free electron lasers and tabletop laser fields.

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“…Building upon earlier research that employed highharmonic radiation [39] , XUV frequency combs [40] , and synchrotron radiation [41] , the coherence and amplitudes of bound states have been extracted from the emission attosecond quantum beat spectrum in hydrogen [42] , where two optical attosecond pulses are used. Quantum-beat signals carrying bound state information have also been mapped onto the photoelectron spectrum [43][44][45][46] . A wave packet in low-lying excited states of the helium atom, oscillating with an ultrashort period of 2.0 fs, has been mapped out [43] .…”

Intensity-surged and Bandwidth-extended Terahertz Radiation in Two-foci Cascading Plasmas

“…The wonderful characteristics of the THz source has already been used in time-resolved terahertz spectroscopy [5][6][7] and transient absorption spectroscopy [8]. The bright broadband THz radiation has potential applications in broadband spectroscopy [9], atomic and molecular ultrafast imaging [10], advanced accelerator technique [11], etc.…”

Electron trajectory backanalysis for spectral profile in two-color terahertz generation

“…Intense broadband terahertz pulses are of enormous interest for multidisciplinary applications ranging from ultrafast spectroscopy, the ultrafast manipulation of electrons in gases [1] and solids [2], to compact electron accelerators [3]. The two-color laser mixing in gas medium [4] is particularly promising for intense supercontinuum terahertz wave generation (TWG) given the absence of emitter damage and absorption [5,6].…”