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  Stadnyk, V.; Andriyevsky, B.; Pryshko, I.; Bychto, L.; Kohut, Z.; Schade, U.; Veber, A.; Puskar, L.; Brezvin, R.: Piezo-optical properties and infrared spectra of Rb₂SO₄ crystals. Optical Materials 157 (2024), p. 116320/1-7

10.1016/j.optmat.2024.116320

Abstract:
The paper deals with the dispersion dependences of birefringence Δni(λ) of the mechanically free and uniaxially clamped Rb2SO4 crystal along different crystal-physical axes at room temperature. It was found that the crystal has an insignificant normal dispersion d(Δnx)/dλ χ ≤ 0, and uniaxial compressions σm do not change the character, but only the slope of the dependences Δni(λ). Uniaxial loads shift the position of the optical isotropic point both in the short-wavelength (σz) and in the long-wavelength part of the spectrum (σy). The spectral dependences of the combined piezo-optical coefficients πo km (λ) were calculated and it was found that they have an insignificant dispersion dependence, and the absolute values of the piezo-optical coefficients πo 31 and πo 21 are equal to each other in the vicinity of the optical isotropic point at the light wavelength λ = 490 nm. The reflection spectra of Rb2SO4 crystals were measured in the infrared range at room temperature using FT-IR spectrometer and synchrotron radiation and the corresponding ab initio calculations of the phonon partial density of states and the dielectric function were performed.