High Kerr nonlinearity of water in THz spectral range

Tcypkin, Anton; Melnik, Maksim; Zhukova, Maria; Vorontsova, Irina; Putilin, S. É.; Kozlov, Sergei A.; Zhang, X.-C.

doi:10.1364/oe.27.010419

Cited by 46 publications

(45 citation statements)

References 42 publications

(51 reference statements)

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“…These mechanisms are well-described with nonlinear refractive index coefficient n 2 as a material characteristic. These findings have now been confirmed experimentally 31,39,40 . Thus, the use of the Z-scan method is justified allowing to calculate the Kerr nonlinearity in the THz frequency range.…”

Section: Methodssupporting

confidence: 64%

“…n 2 dispersion can significantly increase in the region of two-photon resonance with the vibrational mode of the crystal or natural oscillation of the molecule in liquid. For example, in water, oscillations that determine its vibrational nonlinearity in the far IR range of the spectrum have frequency of 15.9 THz while central frequency of used THz radiation is 0.75 THz 39 . Accordingly, up to the frequency values of 8 THz a small dispersion of a vibrational nature in water is expected.…”

Section: Methodsmentioning

confidence: 99%

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Methodical inaccuracy of the Z-scan method for few-cycle terahertz pulses

Melnik

Vorontsova

Putilin

et al. 2019

Sci Rep

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Modern sources of THz radiation generate high-intensity pulses allowing to observe nonlinear effects in this spectral range. To describe many nonlinear effects theoretically, it is necessary to know the nonlinear refractive index coefficient of optical materials. The work studies the applicability of the Z-scan method to determine the nonlinear refractive index coefficient in the THz frequency range for few-cycle pulses. We have discussed the correctness of the known Z-scan method for calculating the nonlinear refractive index coefficient for broadband THz radiation regarding number of cycles pulses have. We have demonstrated that the error in determining the nonlinear refractive index coefficient is always greater than 70% for true single-cycle pulses. With the increase in the number of oscillations to the measurement error shows strong dependence on the sample thickness and can vary from 2% to 90% regarding the parameters chosen. The fact that such radiation dispersion length is commensurate with the nonlinear length or even less than the latter results in the discrepancy mentioned. It is demonstrated that the decrease in the sample thickness leads to the reduction of the nonlinear refractive index coefficient determination error, and this error is <2% when the ratio between the sample thickness and the pulse longitudinal spatial size is ≤1. This can relate to the fact that the nonlinear effects in such a thin sample occur faster than the dispersion ones.

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Section: Methodssupporting

confidence: 64%

Section: Methodsmentioning

confidence: 99%

Methodical inaccuracy of the Z-scan method for few-cycle terahertz pulses

Melnik

Vorontsova

Putilin

et al. 2019

Sci Rep

Self Cite

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show abstract

“…the exciting pulses are strictly bipolar according to Eq. (21) and S E = 0 , the population gratings still arise, even though they have smaller modulation depth. The dependence of the modulation amplitude on the duration and CEP of the pump pulses is determined from Eq.…”

Section: Multi-level Vibration System: Weak Thz Field Strengthmentioning

confidence: 98%

“…Next, the pump power needed to realize coherent interactions in THz range is several orders of magnitude lower, provided that high THz vibrational transitions possess huge dipole moments d 12 20,21 . The latter allows using THz pulses experimentally available to date, and field strengths, significantly lower than in the optical range.…”

mentioning

confidence: 99%

Population difference gratings created on vibrational transitions by nonoverlapping subcycle THz pulses

Архипов

Пахомов

Архипов

et al. 2021

Sci Rep

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We study theoretically a possibility of creation and ultrafast control (erasing, spatial frequency multiplication) of population density gratings in a multi-level resonant medium having a resonance transition frequency in the THz range. These gratings are produced by subcycle THz pulses coherently interacting with a nonlinear medium, without any need for pulses to overlap, thereby utilizing an indirect pulse interaction via an induced coherent polarization grating. High values of dipole moments of the transitions in the THz range facilitate low field strength of the needed THz excitation. Our results clearly show this possibility in multi-level resonant media. Our theoretical approach is based on an approximate analytical solution of time-dependent Schrödinger equation (TDSE) using perturbation theory. Remarkably, as we show here, quasi-unipolar subcycle pulses allow more efficient excitation of higher quantum levels, leading to gratings with a stronger modulation depth. Numerical simulations, performed for THz resonances of the $$H_20$$ H 2 0 molecule using Bloch equations for density matrix elements, are in agreement with analytical results in the perturbative regime. In the strong-field non-perturbative regime, the spatial shape of the gratings becomes non-harmonic. A possibility of THz radiation control using such gratings is discussed. The predicted phenomena open novel avenues in THz spectroscopy of molecules with unipolar and quasi-unipolar THz light bursts and allow for better control of ultra-short THz pulses.

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“…This is especially challenging in the THz range due to lack of brilliant sources [4]. To this aim, a variety of nonlinear laser techniques have been used [16][17][18][19][20][21][22][23][24].…”

Section: Introductionmentioning

confidence: 99%

Nonlinear TeraHertz Transmission by Liquid Water at 1 THz

Novelli

Adhlakha

et al. 2020

Applied Sciences

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The solvation properties of liquid water originate from the transient network of hydrogen-bonded molecules. In order to probe the coupling between the different modes of this network, nonlinear terahertz (THz) spectroscopy techniques are required. Ideally, these techniques should use a minimal volume and capitalize on sensitive field-resolved detection. Here we performed open aperture z-scan transmission experiments on static liquid cells, and detect the THz fields with electro-optical techniques. We show that it is possible to quantify the nonlinear response of liquid water at ~1 THz even when large signals originate from the sample holder windows.

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High Kerr nonlinearity of water in THz spectral range

Cited by 46 publications

References 42 publications

Methodical inaccuracy of the Z-scan method for few-cycle terahertz pulses

Methodical inaccuracy of the Z-scan method for few-cycle terahertz pulses

Population difference gratings created on vibrational transitions by nonoverlapping subcycle THz pulses

Nonlinear TeraHertz Transmission by Liquid Water at 1 THz

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