Vibrational Spectra and Electro‐Optic Effect of Ferroelectric LiNbO3 Crystal

Though being vitally important in telecommunications and modern technology, the basic optic and especially electro‐optic (EO) properties of ferroelectric LiNbO3 crystal (LN) studied from high‐accuracy first‐principles calculation are still not satisfactory. Herein, the electronic structure and vibra...

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Veröffentlicht in:physica status solidi (b) 2023-06, Vol.260 (6), p.n/a
1. Verfasser: Li, Rukang
Format: Artikel
Sprache:eng
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Zusammenfassung:Though being vitally important in telecommunications and modern technology, the basic optic and especially electro‐optic (EO) properties of ferroelectric LiNbO3 crystal (LN) studied from high‐accuracy first‐principles calculation are still not satisfactory. Herein, the electronic structure and vibrational spectra of LN are calculated by the CRYSTAL program. With a hybrid B3LYP functional, the bandgap of 4.8473 eV, refractive indices of no = 2.2339, ne = 2.1440, and nonlinear optical coefficients of d11 = 2.1 pm V−1, d31 = −4.35 pm V−1, and d33 = −27.2 pm V−1 are obtained. It is found that the phonon vibrations are asymmetric along especially the polar axis and the numerically calculated frequencies are strongly dependent on displacement parameters chosen. By averaging displacements to both the positive and negative directions, the obtained vibrational frequencies show excellent agreement to the measured ones except in the range of 320–370 cm−1 where the assignments of the observed ones are in dispute due to extreme low spectral intensities. Based on the calculated vibrational spectra, the clamped dielectric constants of ε11S=38.62 and ε33S=24.17 and clamped EO coefficients of γ33S = 27.08 pm V−1, γ13S = 9.60 pm V−1, γ11S = −5.14 pm V−1, and γ51S = 16.90 pm V−1 are obtained. Herein, it is revealed in the calculation that a single vibration mode at 253 cm−1 makes over 50% contribution to the most important electro‐optic coefficients γ33S and γ13S of LiNbO3 crystal. In addition, this mode is found strongly asymmetric along the polar axis and excellent agreements are obtained by averaging displacements to both the positive and negative directions.
ISSN:0370-1972
1521-3951
DOI:10.1002/pssb.202300051