Vibrational and optical studies of a nonlinear optical crystal, Cs2Bi2O(Ge2O7)

Aneta Ciupa-Litwa; Jan Albert Zienkiewicz; Mariusz Stefanski; Maciej Ptak; Andrzej Majchrowski; Maciej Chrunik

doi:10.1016/j.saa.2021.119816

Vibrational and optical studies of a nonlinear optical crystal, Cs₂Bi₂O(Ge₂O₇)

Spectrochim Acta A Mol Biomol Spectrosc. 2021 Oct 5:259:119816. doi: 10.1016/j.saa.2021.119816. Epub 2021 Apr 20.

Authors

Aneta Ciupa-Litwa¹, Jan Albert Zienkiewicz², Mariusz Stefanski², Maciej Ptak², Andrzej Majchrowski³, Maciej Chrunik³

Affiliations

¹ Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Okólna 2, 50-422 Wrocław, Poland. Electronic address: a.ciupa@intibs.pl.
² Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Okólna 2, 50-422 Wrocław, Poland.
³ Institute of Applied Physics, Military University of Technology, Kaliskiego 2, 00-908 Warszawa, Poland.

PMID: 33989973
DOI: 10.1016/j.saa.2021.119816

Abstract

Single crystals of a non-centrosymmetric and polar Cs₂Bi₂O(Ge₂O₇) compound were grown from melt. This material was characterized by polarized Raman scattering at room temperature. The comparison to the polycrystalline IR and Raman spectra has been made and assignment of all observed modes to the respective vibrations and their symmetry has been proposed. Our results show that this crystal is promising SRS-active nonlinear optical material for up- and down-Raman laser-frequency converters with the most intense lasing line at 481 cm^-1. Optical studies show that Cs₂Bi₂O(Ge₂O₇) exhibits intense absorption bands with peaks maxima at 260 and 293 nm (77 K) typical for ¹S₀→^1,3P₁ transitions of Bi³⁺ ions, which are parity-allowed due to spin-orbit coupling as well as unexpected band centered at 360 nm that was assigned to intervalence charge transfer transition.

Keywords: Non-linear crystals; Optical properties; Pyrogermanate; Raman spectroscopy.