Laser pulse amplitude changes induced by terahertz waves under linear electro-optic effect

Ilyakov, Igor; Китаева, Г. Х.; Shishkin, B. V.; Ахмеджанов, Р. А.

doi:10.1063/1.4871700

Cited by 15 publications

(35 citation statements)

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“…Meanwhile, in the last years sensitive schemes for EO detection based on laser pulse energy changes were suggested [2][3][4][5][6]. We demonstrated both experimentally and theoretically that when the laser pulse interacts with TWR in EO crystal not only its polarization ellipticity but also its energy could be changed [2,3]. These changes depend on the amplitude and phase of the TWR overlapped with the laser pulse and can be used for terahertz time-domain measurements [2,3].…”

mentioning

confidence: 92%

“…We demonstrated both experimentally and theoretically that when the laser pulse interacts with TWR in EO crystal not only its polarization ellipticity but also its energy could be changed [2,3]. These changes depend on the amplitude and phase of the TWR overlapped with the laser pulse and can be used for terahertz time-domain measurements [2,3]. The method based on energy changes can separately measure the energies of the orthogonal polarization components of the laser pulse and, in contrast to techniques based on ellipticity changes, does not require maintaining coherence between the polarization components.…”

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confidence: 99%

“…However, these crystals have high natural birefringence and the use of them with ellipsometric detection technique ( figures 1, a and 1, b) is hindered by decoherence of the laser polarization components [10]. Meanwhile, in the last years sensitive schemes for EO detection based on laser pulse energy changes were suggested [2][3][4][5][6]. We demonstrated both experimentally and theoretically that when the laser pulse interacts with TWR in EO crystal not only its polarization ellipticity but also its energy could be changed [2,3].…”

mentioning

confidence: 99%

“…This technique utilizes ellipticity changes of the laser pulse polarization (the Pockels effect) and is widely used because of its simplicity, high sensitivity and broad operating band of EO crystals. In the report, we present our recent theoretical and experimental study [2][3][4][5][6] of alternative EO detection techniques and compare them with the standard one in terms of their sensitivity and compatibility with different crystals.…”

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confidence: 99%

“…Thus, detection schemes based on this method can potentially be applied to birefringent crystals that are promising for further improvement of the sensitivity of EO time-domain measurements. In our research we applied this technique both with isotropic crystals and with birefringent ones [2][3][4][5][6]. The simplest scheme is based on the total energy changes of the laser pulse.…”

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Terahertz time-domain measurements by electro-optic crystals with various symmetries

et al. 2017

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Terahertz wave radiation (TWR) is attractive due to its applications in spectroscopy, communication technologies, biology, medical science and other fields. One of the popular ways of TWR time-domain measurements is based on its nonlinear-wave interaction with femtosecond laser pulses in electro-optic (EO) crystals [1]. This technique utilizes ellipticity changes of the laser pulse polarization (the Pockels effect) and is widely used because of its simplicity, high sensitivity and broad operating band of EO crystals. In the report, we present our recent theoretical and experimental study [2-6] of alternative EO detection techniques and compare them with the standard one in terms of their sensitivity and compatibility with different crystals.When linearly polarized laser pulse propagates in isotropic crystal (for example ZnTe or GaP) then in the absence of terahertz electric field its polarization doesn't change. However, in the presence of electric field a refractive index tensor of the crystal is changed and the crystal becomes anisotropic. As a result, orthogonal polarization components of the laser pulse transmit through the matter with different optical densities and the laser pulse polarization becomes elliptic. This polarization ellipticity is measured by an appropriate optical scheme (figure 1, a) and terahertz electric field overlapped with the laser pulse is determined. This technique can be used with TWR generated by sources directed by femtosecond laser pulses [1] and from external sources (not synchronized with the laser system) emitting both continuous [7] and pulsed radiation [8]. In spite of high sensitivity of the technique, we have shown that sensitivity of EO measurements can be increased. The sensitivity improvement can be achieved by use of laser pulses with an edge-cut spectrum [4][5][6]. A new experimental scheme is presented in figure 1, b. An edge filter is positioned before the EO crystal to produce a high gradient of the spectral energy density of the laser pulse and the TWR interacted with the laser pulse that had previously passed through an edge filter. It was shown theoretically [5] that changes of polarization ellipticity at the frequencies corresponding to the edge-cut of the laser pulse spectrum could be much higher than those could when laser pulse with Gaussian spectrum is used. To utilize the ellipticity changes at the frequencies corresponding to the edge-cut of the laser pulse spectrum, the laser pulse after the EO crystal can be decomposed in the frequency spectrum by a diffraction grating or can be passed through another edge filter transmitting only the optical waves with frequencies corresponding to the slope of the first filter [5,6] (figure 1, b). The ellipticity changes are measured using an appropriate optical scheme. In works [5,6] the scheme depicted in figure 1, b was implemented with GaP crystal. This crystal has no natural birefringence and the new technique demonstrated a much stronger response on the same TWR than the standard one ( figure 2, a). The method b...

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confidence: 92%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Terahertz time-domain measurements by electro-optic crystals with various symmetries

et al. 2017

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Solid‐State Molecular Motions in Organic THz Generators

Kim

Park

Seok

et al. 2020

Advanced Optical Materials

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Organic nonlinear optical salt crystals are widely used as efficient broadband THz generators. Although solid state molecular motions of organic crystals can greatly influence THz generation characteristics, their origin and effects on THz photonics are not clearly identified. In this work, the origin of solid‐state molecular motions of the state‐of‐the‐art nonlinear optical organic salt crystals and their effects on THz generation characteristics are theoretically investigated. A model crystal, HMQ‐TMS (2‐(4‐hydroxy‐3‐methoxystyryl)‐1‐methylquinolinium 2,4,6‐trimethylbenzenesulfonate) with large macroscopic optical nonlinearity, which is very attractive for intense broadband and narrowband THz wave generation, is chosen. The solid‐state molecular vibrations of HMQ‐TMS crystals can be classified in three frequency regions: phonon mode region, intramolecular motion region, and their mixing region. For the first time for ionic organic crystalline THz generators, the contributions of cationic chromophores and anionic matchmakers on each of vibrational modes are quantitatively separated. In addition, the influence of solid‐state molecular vibrations of HMQ‐TMS crystals on the generated THz spectra is investigated. These results provide an essential information for design of new organic nonlinear optical salt crystals for THz generators as well as detectors and for optimization of THz generation performance.

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Molecular crystals and thin films for photonics

Jazbinšek

Günter

2019

Handbook of Organic Materials for Electronic and Photonic Devices

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Laser pulse amplitude changes induced by terahertz waves under linear electro-optic effect

Cited by 15 publications

References 13 publications

Terahertz time-domain measurements by electro-optic crystals with various symmetries

Terahertz time-domain measurements by electro-optic crystals with various symmetries

Solid‐State Molecular Motions in Organic THz Generators

Molecular crystals and thin films for photonics

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