Phase-resolved two-dimensional spectroscopy based on collinear n-wave mixing in the ultrafast time domain

Kuehn, W.; Reimann, K.; Woerner, M.; Elsaesser, Thomas

doi:10.1063/1.3120766

Cited by 92 publications

(87 citation statements)

References 27 publications

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“…It is now possible, for example, to control the alignment of gasphase molecules (4) and antiferromagnetic spin waves (5), drive an insulator-to-metal transition in oxides such as VO 2 (6), and break up Cooper pairs in a superconductor with intense THz pulses (7). Nonlinear THz interactions have also enabled the first demonstrations of 2D THz spectroscopy in a double quantum well system and graphene (8,9).…”

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confidence: 99%

Coherent two-dimensional terahertz-terahertz-Raman spectroscopy

Finneran

Welsch

Allodi

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

108

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We present 2D terahertz-terahertz-Raman (2D TTR) spectroscopy, the first technique, to our knowledge, to interrogate a liquid with multiple pulses of terahertz (THz) light. This hybrid approach isolates nonlinear signatures in isotropic media, and is sensitive to the coupling and anharmonicity of thermally activated THz modes that play a central role in liquid-phase chemistry. Specifically, by varying the timing between two intense THz pulses, we control the orientational alignment of molecules in a liquid, and nonlinearly excite vibrational coherences. A comparison of experimental and simulated 2D TTR spectra of bromoform (CHBr 3 ), carbon tetrachloride (CCl 4 ), and dibromodichloromethane (CBr 2 Cl 2 ) shows previously unobserved off-diagonal anharmonic coupling between thermally populated vibrational modes.ultrafast dynamics | terahertz | coherent multidimensional spectroscopy D etailed molecular pictures of the structure and dynamics of liquids drive our understanding of chemistry and biology. Nonlinear 2D infrared and NMR spectroscopies have revealed many specifics of liquid behavior, monitoring the coupling, spectral diffusion, and homogeneous linewidths of intramolecular vibrations and nuclear spins (1, 2). However, the motions that directly participate in solvation and chemical reactivity are manifest in the terahertz (THz) region of the spectrum, making 2D THz studies especially valuable. To date, no 2D technique has been demonstrated that incorporates multiple THz interactions with a liquid.Recent advances in pulsed, high-power THz sources with electric fields exceeding 100 kV/cm have enabled a new generation of nonlinear THz spectroscopy, in which THz radiation is used to both manipulate and record the response of matter (3). It is now possible, for example, to control the alignment of gasphase molecules (4) and antiferromagnetic spin waves (5), drive an insulator-to-metal transition in oxides such as VO 2 (6), and break up Cooper pairs in a superconductor with intense THz pulses (7). Nonlinear THz interactions have also enabled the first demonstrations of 2D THz spectroscopy in a double quantum well system and graphene (8, 9).With weak transition dipole moments yet high THz absorptivity, liquids present many challenges with respect to the development of 2D THz spectroscopy. Initial successes with 2D Raman spectroscopy were later shown to suffer from the interference of cascaded processes (10-12), but new schemes using optical pulse shaping have eliminated the cascaded contributions (13). An alternative approach is resonant 2D THz spectroscopy, analogous to 2D IR spectroscopy. However, this method is hindered by a lack of THz directional phase matching, leading to signals that can be easily overwhelmed by a strong linear background. In the last few years, hybrid optical-THz techniques that circumvent these challenges have emerged, including 2D Raman-THz spectroscopy and THz Kerr effect spectroscopy (14-16). Here, we present the complementary 2D TTR spectroscopy, a natural extension of these hybrid te...

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confidence: 99%

Coherent two-dimensional terahertz-terahertz-Raman spectroscopy

Finneran

Welsch

Allodi

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

108

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“…Let us also note that Fourier transform (or timedomain) spectroscopy is routinely used in the THz domain [24,25], where grating-based spectrometers and cameras are not readily available. 2D THz spectroscopy has been demonstrated on inter-subband excitonic transitions in QW structures using electrooptic sampling in a collinear geometry [26,27,28]. In the following, we will focus on the experimental methods that address inter-band transitions in the optical (visible) domain -sometimes referred to as electronic spectroscopy since it probes the electronic degrees of freedom, as opposed to vibrational spectroscopy.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…Theory has shown that the strength of the X hh is enhanced, and its line shape is dispersive due to many-body interactions. 26,29 The second row of Fig. 3 shows the cocircular polarized 2DFT spectrum, where the strength of the X hh peak and its dispersive line shape indicate the continued dominance of many-body interactions.…”

Section: Heavy and Light Hole Excitons In Gaas Qwsmentioning

confidence: 99%

Multidimensional coherent optical spectroscopy of semiconductor nanostructures: a review

Nardin

2015

Semicond. Sci. Technol.

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Abstract. Multidimensional Coherent optical Spectroscopy (MDCS) is an elegant and versatile tool to measure the ultrafast nonlinear optical response of materials. Of particular interest for semiconductor nanostructures, MDCS enables the separation of homogeneous and inhomogeneous linewidths, reveals the nature of coupling between resonances, and is able to identify the signatures of many-body interactions. As an extension of transient Four-Wave Mixing (FWM) experiments, MDCS can be implemented in various geometries, in which different strategies can be used to isolate the FWM signal and measure its phase. I review and compare different practical implementations of MDCS experiments adapted to the study of semiconductor materials. The power of MDCS is illustrated by discussing experimental results obtained on semiconductor nanostructures such as quantum dots, quantum wells, microcavities, and layered semiconductors.

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“…We do this using amplitude-and phaseresolved two-dimensional spectroscopy at 2 THz [4]. We demonstrate that the third-order response is dominated by pump-probe signals.…”

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confidence: 99%

“…[4]. A phase-locked pair of pulses centred at 2 THz propagate parallel to one another and are focused onto the graphene sample where they spatially overlap.…”

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confidence: 99%

Ultrafast two-dimensional THz spectroscopy of graphene

Bowlan

Moreno

Reimann

et al. 2013

EPJ Web of Conferences

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Abstract. With two-dimensional THz spectroscopy the dynamics of low-energy carriers in graphene is determined. Both intra-and interband absorption contribute to the observed ultrafast pump-probe signals.Graphene, or a single layer of graphite, has a peculiar bandstructure, which allows for the study of massless charge carriers with a velocity independent of their energy. Charge transport in graphene has been widely explored but there is still much to be learned about carrier dynamics on the ultrafast time scale, in particular at very small energies close to the K and K' (Dirac) points in k-space. So far, there have been ultrafast pump-probe studies of graphene using higher energies to excite off-equilibrium carriers [1,2]. Thermalization occurred within 250 fs due to Coulomb and optical phonon scattering. Later cooling occurs from interactions with optical and finally with acoustic phonons. Carrier dynamics at energies close to the Dirac point (E = 0), well below the optical phonon energy, should be quite different, as shown by recent mid-infrared measurements [3].Here we present the first nonlinear THz study of graphene. We do this using amplitude-and phaseresolved two-dimensional spectroscopy at 2 THz [4]. We demonstrate that the third-order response is dominated by pump-probe signals. These reveal an induced absorption that decays with a time constant as short as 2.5 ps depending on the sample temperature. At lower temperatures an additional slower component (≈10 ps) is present. We attribute this to a combination of intra-and interband absorption followed by thermalization. The absence of any other nonlinear signal points to a very short decoherence time of THz excitations in graphene.The 2D THz measurements are based on the method presented in Ref. [4]. A phase-locked pair of pulses centred at 2 THz propagate parallel to one another and are focused onto the graphene sample where they spatially overlap. The total transmitted electric field is measured in (real) time t with electro-optic sampling, for each delay τ between the two pulses [ Fig. 1(a)]. Using two choppers, the two THz pulses are also measured individually, so that they can be subtracted from the measured total signal to isolate the nonlinear part ( Fig. 1(b)). The measured electric field is proportional to the current in the sample. As explained in Ref.[4], the various contributions to the nonlinear signal can be separated in two-dimensional frequency space, and then transformed back to the time domain. We used a 40 layer C-face epitaxial graphene sample (from Graphene Works).We measured the 2 THz pump-probe signals from the graphene sample at T = 20 K. Pulse A had a field strength of 5 kV/cm and pulse B was 8 kV/cm. The pump-probe signal was π phase shifted with respect to the driving electric field (pulse B) indicating an induced transient absorption. The enhanced absorption as a function of pump-probe delay τ was measured at several temperatures (pump-probe signal B, Fig. 1d). With increasing temperature, the picosecond decay of the enhanced a...

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Phase-resolved two-dimensional spectroscopy based on collinear n-wave mixing in the ultrafast time domain

Cited by 92 publications

References 27 publications

Coherent two-dimensional terahertz-terahertz-Raman spectroscopy

Coherent two-dimensional terahertz-terahertz-Raman spectroscopy

Multidimensional coherent optical spectroscopy of semiconductor nanostructures: a review

Ultrafast two-dimensional THz spectroscopy of graphene

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