Nonlinear terahertz coherent excitation of vibrational modes of liquids

Allodi, Marco A.; Finneran, Ian A.; Blake, Geoffrey A.

doi:10.1063/1.4938165

Cited by 29 publications

(41 citation statements)

References 39 publications

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“…The electronic and nuclear alignment of the molecules follows the polarization of the THz radiation (15,16). Thus, we posit that the change in the measured birefringence as a function of t 1 is due to angular control of the molecular alignment induced by the THz polarization (Fig.…”

Section: Significancementioning

confidence: 86%

“…The transient birefringence in the sample is probed with a small portion of the 800-nm light from the amplifier, and sent down a second delay line (t 2 ). As described in our previous work, we heterodyne detect the transient birefringence using a 10 5 :1 polarizer, a λ/4 plate, a Wollaston prism, and a pair of silicon photodiodes (16). The signal is isolated with differential chopping of the signal and idler beams and detected with a lock-in amplifier (SI Appendix, Experimental Setup).…”

Section: Methodsmentioning

confidence: 99%

“…The electronic and orientational components of the measured signal are due to a change in the sample birefringence, or a difference in refractive index along the vertical and horizontal directions. The birefringent signal is predicted using the measured THz fields (15,16). More details of the model are given in SI Appendix, Orientational Model.…”

Section: Methodsmentioning

confidence: 99%

“…1B, Right; it is an extension of the model used in our previous work (ref. 16 and SI Appendix, Orientational Model). The orientational model correctly predicts the sign changes and zero crossings of the birefringence, although it does not account for the nonlinear vibrational coherences.…”

Section: Significancementioning

confidence: 99%

“…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)(15)(16). Here, we present the complementary 2D TTR spectroscopy, a natural extension of these hybrid techniques, that was described theoretically by Cho in 1999 (10,17,18).…”

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confidence: 99%

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Coherent two-dimensional terahertz-terahertz-Raman spectroscopy

Finneran

Welsch

Allodi

et al. 2016

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

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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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Section: Significancementioning

confidence: 86%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Significancementioning

confidence: 99%

mentioning

confidence: 99%

See 3 more Smart Citations

Coherent two-dimensional terahertz-terahertz-Raman spectroscopy

Finneran

Welsch

Allodi

et al. 2016

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

Self Cite

108

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Highly Nonlinear Optical Organic Crystals for Efficient Terahertz Wave Generation, Detection, and Applications

Kim

Kang

Puc

et al. 2021

Advanced Optical Materials

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ordering in the crystalline state should be simultaneously considered when designing organic π-conjugated crystals to achieve the desired physical properties. However, the prediction of the molecular ordering of organic π-conjugated chromophores in the crystalline state is still significantly difficult. This is because most organic π-conjugated chromophores exhibit several complex intermolecular and intramolecular interactions (and interionic interactions) with multiple possible molecular conformations during the self-assembling process in the crystalline state. [17,18] For each specific target application, a different targeted control of the molecular ordering of chromophores in the crystalline state is required, which is still an important issue in the molecular (and crystal) engineering of various organic π-conjugated crystalline materials.This issue is more critical for organic nonlinear optical (NLO) crystals and will be the focus of this review. Organic NLO crystals can be used in diverse nonlinear photonic applications, such as frequency down-and up-conversion, terahertz (THz) wave generation and detection, phase and amplitude electro-optic modulation, and high-speed telecommunication integrated optics. [19][20][21][22][23] Organic crystals must possess a noncentrosymmetric molecular ordering of chromophores to achieve second-order optical nonlinearity. However, in addition to the aforementioned complicated molecular interactions, the introduction of strong polar substituents (electron-donating groups (EDGs) and electron-withdrawing groups (EWGs)) on widely used push-pull π-conjugated chromophores to increase their molecular nonlinearity also increases their dipole moment. In many cases, a high dipole moment leads to a centrosymmetric ordering of chromophores with antiparallel dipole-dipole aggregation in the crystalline state (i.e., there is no macroscopic second-order optical nonlinearity). This tendency further complicates the development of new organic NLO crystals with large second-order optical nonlinearity. This is one of the reasons for only a few classes of organic crystals with state-of-theart optical nonlinearity being reported in the last few decades. Moreover, in addition to large macroscopic second-order optical nonlinearity, different NLO applications require different targeted physical properties (e.g., refractive index, dispersion of the refractive index, dielectric constant, and absorption coefficient) and crystal characteristics (e.g., direction of the polar axis, morphology, aperture size, thickness, and facets). Therefore, it Organic π-conjugated crystals with second-order optical nonlinearity are considerably attractive materials for diverse terahertz (THz) wave photonics. An overview of the research of organic nonlinear optical (NLO) crystals for THz wave generation, detection, and applications is provided here. First, the status of organic NLO crystals compared to other alternative THz materials is described. Second, the basic theory and requirements for organic THz generators and d...

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Two-Dimensional Spectroscopy at Terahertz Frequencies

Zhang

et al. 2018

Top Curr Chem (Z)

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Multidimensional spectroscopy in the visible and infrared spectral ranges has become a powerful technique to retrieve dynamic correlations and couplings in wide-ranging systems by utilizing multiple correlated light-matter interactions. Its extension to the terahertz (THz) regime of the electromagnetic spectrum, where rich material degrees of freedom reside, however, has been progressing slowly. This chapter reviews some of the THz-frequency two-dimensional (2D) spectroscopy techniques and experimental results realized in recent years. Examples include gas molecule rotations, spin precessions in magnetic systems, and liquid molecular dynamics studied by 2D THz or hybrid 2D THz-Raman spectroscopy techniques. The methodology shows promising applications to different THz-frequency degrees of freedom in various chemical systems and processes.

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Nonlinear terahertz coherent excitation of vibrational modes of liquids

Cited by 29 publications

References 39 publications

Coherent two-dimensional terahertz-terahertz-Raman spectroscopy

Coherent two-dimensional terahertz-terahertz-Raman spectroscopy

Highly Nonlinear Optical Organic Crystals for Efficient Terahertz Wave Generation, Detection, and Applications

Two-Dimensional Spectroscopy at Terahertz Frequencies

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