Raman spectra of lithium niobate crystals heavily doped with zinc and magnesium

We have examined the Raman spectra of heavily doped lithium niobate single crystals (at close-to-threshold concentrations of doping cations): LiNbO 3 :Zn (4.5 mol % ZnO), LiNbO 3 :Mg (5.01 mol %):Fe (0.005 mol %), LiNbO 3 :Mg (5.1 mol %), and LiNbO 3 :Mg (5.3 mol % MgO). Low-intensity lines with fre...

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Bibliographic Details
Published in:Optics and spectroscopy 2016-12, Vol.121 (6), p.842-850
Main Authors: Sidorov, N. V., Palatnikov, M. N.
Format: Article
Language:English
Subjects:
Condensed-Matter Spectroscopy
Lasers
Optical Devices
Optics
Photonics
Physics
Physics and Astronomy
Raman spectra
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Summary:We have examined the Raman spectra of heavily doped lithium niobate single crystals (at close-to-threshold concentrations of doping cations): LiNbO 3 :Zn (4.5 mol % ZnO), LiNbO 3 :Mg (5.01 mol %):Fe (0.005 mol %), LiNbO 3 :Mg (5.1 mol %), and LiNbO 3 :Mg (5.3 mol % MgO). Low-intensity lines with frequencies at 209, 230, 298, 694, and 880 cm –1 have been revealed for the first time. Analysis of the data from the literature on lattice dynamics calculations from first principles (ab initio) does not make it possible to unambiguously state that these lines correspond to fundamental vibrations of the А 2 symmetry species, which are forbidden for the С 3 V 6 ( R3c ) space group. At the same time, ab initio calculations unambiguously indicate that the experimentally observed low-intensity “superfluous” lines with the frequencies at 104 and 119 cm –1 cannot correspond to vibrations of the А 2 symmetry species. It is most likely that they correspond to two-particle states of acoustic phonons with a total wave vector equal to zero.
ISSN:0030-400X
1562-6911
DOI:10.1134/S0030400X16120225