Structure and Optical Properties of Langasite Family Crystals (La1–xNdx)3Ga5SiO14 (x = 0, 0.4, 0.6, 1)

The structure and optical properties of langasite family crystals (La 1– x Nd x ) 3 Ga 5 SiO 14 with different Nd contents have been studied. The optical rotation ρ for these crystals has been calculated from the measured polarized-light transmission spectra. It is shown that, at a small ρ value (~3...

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Bibliographic Details
Published in:Crystallography reports 2023-10, Vol.68 (5), p.732-743
Main Authors: Golovina, T. G., Konstantinova, A. F., Dudka, A. P., Butashin, A. V., Umanskii, B. A., Kozlova, N. S., Kasimova, V. M., Zabelina, E. V.
Format: Article
Language:English
Subjects:
Absorption spectra
Angles (geometry)
Crystallography and Scattering Methods
Crystals
Dichroism
Electron density
Light transmission
Mathematical analysis
Optical activity
Optical properties
Optical rotation
Parameters
Physical Properties of Crystals
Physics
Physics and Astronomy
Polarizers
Refractivity
Unit cell
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Summary:The structure and optical properties of langasite family crystals (La 1– x Nd x ) 3 Ga 5 SiO 14 with different Nd contents have been studied. The optical rotation ρ for these crystals has been calculated from the measured polarized-light transmission spectra. It is shown that, at a small ρ value (~3–5 deg/mm), the transmission spectra recorded at different angles between polarizers (e.g., ±45°) should be used to obtain the best results, rather than the transmission spectra at parallel and crossed polarizers, as is generally accepted. The circular dichroism of these crystals has been measured. The relationship between the circular-dichroism bands and the change in the optical rotation near the absorption bands has been determined using the Kramers–Kronig relations. Variances of the parameter ρ with allowance for absorption in the wavelength range of 400–1000 nm have been calculated for (La 0.6 Nd 0.4 ) 3 Ga 5 SiO 14 , (La 0.4 Nd 0.6 ) 3 Ga 5 SiO 14 , and Nd 3 Ga 5 SiO 14 crystals and compared with the variance of ρ for a La 3 Ga 5 SiO 14 langasite crystal. The mean refractive indices and parameters of optical activity of these crystals have been calculated from the structural data. It is shown that the dependences of the mean refractive index and parameter ρ, calculated within the no-absorption approximation, on the unit-cell parameters are linear. Note that the dependence observed for experimental ρ values is not linear, which is related to the influence of absorption and structural features (nonlinear change in the geometry of optically active regions of the electron density when La is partially replaced with Nd).
ISSN:1063-7745
1562-689X
DOI:10.1134/S106377452360045X