Broadband terahertz time-domain spectroscopy of ferroelectric LiTaO3: Phonon-polariton dispersion

Kojima, Seiji; Mori, Tatsuya

doi:10.1063/1.4901657

Cited by 13 publications

(7 citation statements)

References 14 publications

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“…The real and imaginary parts of the refractive index clearly show the sharp resonance at the lowest TO mode frequency near =2.7 THz. Such behavior is very similar to that of a lithium tantalite crystal [20].…”

Section: Real and Imaginary Parts Of Refractive Index Of Strontium Tisupporting

confidence: 62%

Terahertz time-domain spectroscopy of Raman inactive phonon-polariton in strontium titanate

Kojima

Mori

2016

Ferroelectrics

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The Raman inactive low-frequency phonon-polariton was studied in a quantum paraelectric strontium titanate crystal. The lowest frequency IR active T 1u mode was investigated by the reflectance and transmittance Terahertz Time-Domain Spectroscopy using the pulse coherent THz radiation from 0.2 to 5.0 THz. The complex dispersion relations were determined using the real and imaginary parts of a polariton wavevector calculated from the complex refractive index which reflects the T 1u symmetry phonon-polariton. The remarkable change of the dispersion relation was observed in the vicinity of TO and LO mode frequencies for both real and imaginary parts of a polariton wave vector. The observed complex dispersion relation of T 1u symmetry is in agreement within the experimental uncertainty with the dispersion curves fitted by the damped harmonic oscillator model.

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Section: Real and Imaginary Parts Of Refractive Index Of Strontium Tisupporting

confidence: 62%

Terahertz time-domain spectroscopy of Raman inactive phonon-polariton in strontium titanate

Kojima

Mori

2016

Ferroelectrics

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“…In order to determine the phonon-polariton dispersion relation, we calculated the wave vector of the polariton according to Huang's dispersion relation [13,25]: where v, k, c, and e k; v ð Þ are the angular frequency, wave vector, light velocity, and dielectric constant, respectively. In the last several decades, the polariton dispersion relation was observed in many crystals by Raman scattering and THz-TDS experiments [15][16][17][18]. However, there is no specific information on the dispersion relation and the damping of phonon polaritons in a BZO single crystals.…”

Section: Methodsmentioning

confidence: 97%

“…After the discovery of polariton dispersion in a Gallium phosphide, GaP, crystal [15], nowadays, extensive experimental and theoretical research has been carried out in many crystals [16][17][18]. The recent THz-TDS measurements on a BZO single crystal has been revealed that the lowest-frequency IR active transverse optic (TO) phonon mode near 2 THz exhibit a clear softening upon cooling from 300 to 8 K [8].…”

Section: Introductionmentioning

confidence: 98%

Terahertz time-domain spectroscopy and Raman scattering studies of incipient ferroelectric BaZrO₃

2016

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We have studied an incipient ferroelectric BaZrO 3 single crystal with perovskite structure by terahertz time-domain and Raman scattering spectroscopies. The phonon-polariton dispersion relation of the lowfrequency infrared active TO1 and TO2 modes was studied from the real and imaginary parts of the complex dielectric constants at 8 K. The experimentally observed complex polariton dispersion relations are discussed by a damped harmonic oscillator model. First-order Raman active modes, forbidden in cubic Pm3m symmetry, have been observed in a BaZrO 3 single crystal, indicating the lowering of cubic symmetry.

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“…24,25) Therefore, in the study of the polariton dispersion of ferroelectrics, an analysis including the damping of polaritons is important. [26][27][28] When the dielectric constant "ðk; !Þ is complex, the wave vector k or frequency ω can be a complex number. Usually in IR spectroscopy, ω is defined as a real number, while k is defined as a complex number; 20) thus, polariton damping was discussed by the imaginary part of k. The real and imaginary parts of k were determined by refraction and extinction coefficients determined from a dielectric constant.…”

Section: Polariton Dispersion Relationmentioning

confidence: 99%

“…29) The determination of a complex polariton dispersion relation can be measured by terahertz time-domain spectroscopy (THz-TDS), while the available highest frequency is around 160 cm −1 , which is close to the lowest E(TO1) mode frequency and much lower than the lowest A 1 (TO1) mode frequency. 26,27) The polariton dispersion relation for A 1 (z) symmetry was determined by the refraction and extinction coefficients measured along the c-axis shown in Fig. 3(b).…”

Section: Polariton Dispersion Relationmentioning

confidence: 99%

Optical phonons and polariton dispersions of congruent LiNbO₃ studied by far-infrared spectroscopic ellipsometry and Raman scattering

Kojima¹,

Kanehara²,

Hoshina³

et al. 2016

Jpn. J. Appl. Phys.

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IR active optical modes and phonon–polaritons with E(x) and A1(z) symmetries were studied in a ferroelectric congruent lithium niobate crystal. The real and imaginary parts of a dielectric constant along the a- and c-axes were accurately determined by far-infrared spectroscopic ellipsometry (FIRSP) from 40 to 700 cm−1. For the nine transverse optical (TO) modes with E(x) symmetry, it was difficult to observe the 5th E(TO5) mode at 361 cm−1 and the 9th E(TO9) mode at 665 cm−1 by Raman scattering owing to the very low Raman intensity, while these modes were clearly observed by FIRSP. In contrast, the 6th E(TO6) mode at 371 cm−1 was not observed by FIRSP owing to the very weak absorption, while it was clearly observed by Raman scattering. All the four TO modes with A1(z) symmetry were clearly observed independently by FIRSP and Raman scattering. The dispersion relations of phonon–polaritons including the damping of polaritons were determined using the real and imaginary parts of a polariton wavevector calculated from complex dielectric constants. The polariton dispersion of the lowest A1(z) mode at 254 cm−1 is in agreement with the previous forward Raman scattering experiment; however, any anticrossing predicted by the previous impulsive Raman scattering experiment was not observed.

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Broadband terahertz time-domain spectroscopy of ferroelectric LiTaO3: Phonon-polariton dispersion

Cited by 13 publications

References 14 publications

Terahertz time-domain spectroscopy of Raman inactive phonon-polariton in strontium titanate

Terahertz time-domain spectroscopy of Raman inactive phonon-polariton in strontium titanate

Terahertz time-domain spectroscopy and Raman scattering studies of incipient ferroelectric BaZrO₃

Optical phonons and polariton dispersions of congruent LiNbO₃ studied by far-infrared spectroscopic ellipsometry and Raman scattering

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Broadband terahertz time-domain spectroscopy of ferroelectric LiTaO3: Phonon-polariton dispersion

Cited by 13 publications

References 14 publications

Terahertz time-domain spectroscopy of Raman inactive phonon-polariton in strontium titanate

Terahertz time-domain spectroscopy of Raman inactive phonon-polariton in strontium titanate

Terahertz time-domain spectroscopy and Raman scattering studies of incipient ferroelectric BaZrO3

Optical phonons and polariton dispersions of congruent LiNbO3 studied by far-infrared spectroscopic ellipsometry and Raman scattering

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Product

Resources

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Terahertz time-domain spectroscopy and Raman scattering studies of incipient ferroelectric BaZrO₃

Optical phonons and polariton dispersions of congruent LiNbO₃ studied by far-infrared spectroscopic ellipsometry and Raman scattering