REFRACTOMETRY OF UNIAXIALLY COMPRESSED Rb2SO4 CRYSTALS

Vasyl Stadnyk, Vasyl Vyshnevskyi, Igor Matviishyn, Vasyl Baliha, Roman Lys

Abstract


Introduction. The refractive index  of a crystal is its fundamental characteristic. In the presence of the experimentally obtained dispersion n(λ)  with high accuracy, it is possible to determine the fundamental characteristics of single crystals using analytical relations for the refractive index in the region of crystal transparency.

Materials and Methods. In this work, high-optical-quality rubidium sulfate (Rb2SO4) single crystals were synthesized, crystallographic orientation was determined using a polarization microscope and conoscopic figures, and the dispersion of the refractive indices nx(λ) was studied using the Obreimov immersion method at room temperature for different directions of uniaxial compression with stress magnitude of  σm ~ 100 bar.

Results and Discussion. It was found that the refractive indices dispersion of this crystal ni(λ) is normal (dn/dλ < 0 ). As the fundamental absorption edge is approached, it increases sharply for the three polarization directions of the electromagnetic wave. The refractive indices satisfy the inequalities nx >= nz > ny and dnx/dλ > dnz/dλ > dny/dλ.

The baric changes in the molar refraction Ri, electronic polarizability ai (for the wavelength λ = 500 nm), and crystal-optical parameters (spectral positions of the effective centers of ultraviolet and infrared oscillators, as well as their effective strengths) of Rb2SO4 crystals at room temperature were calculated. It was found that uniaxial pressures of  σ ~ 100 bar led to an increase in electronic polarizability of the crystal by an average of (1 – 3)×10–26 cm3.

Conclusion. It was established that uniaxial pressures lead to an increase in contributions from infrared oscillators by 2–5 %, primarily due to the baric dependence of the optical isotropic point. They also shift the position of the effective strength of the ultraviolet oscillator λ0i toward the short-wavelength region of the spectrum. The change in the effective oscillator strength in this baric range does not exceed 1 %. It was found that the positions of effective absorption bands are more sensitive to uniaxial pressures than the effective strengths of the corresponding oscillators.

Keywords: refractive indices, uniaxial compression, refraction, electronic polarizability, band gap width.


Full Text:

PDF

References


  1. Romaniuk M. O. Crystal optics. Lviv, Ivan Franko LNU, 2017, 456 p. (in Ukrainian).
  2. Romaniuk M. O., Krochuk A S., Pashuk I. P. Optics. Lviv, Ivan Franko LNU, 2012, 562 p. (in Ukrainian).
  3. Stadnyk V. Yo., Romaniuk M. O., Brezvin R. S. Electronic polarizability of ferroics: Monograph. Lviv, Ivan Franko LNU, 2014, 306 p. (in Ukrainian).
  4. Stadnyk V. Yo., Haba V. M. Refractometry of crystals with incommensurate phases: Monograph. Lviv, Liha-Pres, 352 p. (in Ukrainian).
  5. Shi Q., Dong L., Wang Y. (2023). Evaluating refractive index and birefringence of nonlinear optical crystals: Classical methods and new developments. Chinese Journal of Structural Chemistry, 42(1), 100017.
  6. Wang S. Ren T., Yang P., Saito M., Brindley H. E. (2024). Improved Temperature-Dependent Ice Refractive Index Compilation in the Far-Infrared Spectrum. Geophysical Research Letters, 51(14), 1-10.
  7. Ren T., Yang P., Brindley H. E., L’Ecuyer T. S., Maestri T. (2025). Temperature dependent optical properties of ice crysral in far-infrared regime. Geophysical Research Letters, 52(12), 1-11.
  8. Herbin H., Deschutter L., Deguine A., Petiprez D. (2023). Complex refractive index of crystalline quartz particles from UV to thermal infrared. Aerosol Science and Technology, 57(3). 255-265.
  9. Jin S. R., Sweeney S. J., Adams A. R., Higashi T., Riechert H., Thijs P. J. A. (2003). Wavelength dependence of the modal refractive index in 1.3 μm InGaAsP, AlGaInAs and GaInNAS lasers using high pressure. Physica Status Solidi (b), 235(2), 491-495.
  10. Jones S. C., Vaughan B. A. M. and Gupta Y. M. (2001). Refractive indices of sapphire under elastic, uniaxial strain compression along the a axis. Journal of Applied Physics, 90(10), 4990–4996.
  11. Jones S. C., Robinson M. C., Gupta Y. M. (2003). Ordinary refractive index of sapphire in uniaxial tension and compression along the c axis. Journal of Applied Physics, 93(2), 1023–1031.
  12. Uchino K., Nomura S., Vedam K., Newnham R. E., Cross L. E. (1984). Pressure dependence of the refractive index and dielectric constant in a fluoroperovskite, KMgF3. Physical Review B, 29, 6921–6925.
  13. Fousek J. (1978). Reftactive indices and electro-optics at ferroelectrics and structural phase. Ferroelectrics, 20(1), 11–20.
  14. Stadnyk V. Yo., Romanyuk M. O. (2005). The baric changes of the electron polarisability of LiRbSO4, LiKSO4 and (NH4)2BeF4 crystals. Ferroelectrics, 317(1), 63–68.
  15. Stadnyk V. Yo., Romanyuk M. O. (2005). The refractive properties of uniaxially stressed doped TGS crystals. Ferroelectric, 317(1), 95–99.
  16. Stadnyk V. Yo., Romanyuk M. O., Chyzh O. Z., Vachulovych V. F. (2007). The baric changes of the refractive properties of K2SO4 crystals. Condensed Matter Physics, 10(1), 45–60.
  17. Muller O., Roy R. The Major ternary structural families. Berlin, Heidelberg and New York (Springer-Verlag), 1974, 487 p.
  18. Rudysh M. Ya., Pryshko I. A., Shchepanskyi P. A., Stadnyk V. Yo., Brezvin R. S., Kogut Z. O. (2022). Optical and electronic parameters of Rb2SO4 crystals. Optik, 269, 69875.
  19. Gaba V.M. (2010). Temperature-and-Spectral Deformations of the Optical Indicatrix of Rubidium Sulphate Single Crystal. Acta Physica Polonica A, 117(1), 129-132.
  20. Shchepanskyi P. A., Stadnyk V. Yo., Pryshko I. A., Brezvin R. S., Onufriv O. R., Kohut Z. (2024). Сhanges in thermal and refractive parameters of the sulfate group crystals in the region of the phase transition. Journal of Physical Studies, 28(1), 1701(1-7).
  21. Pryshko I. A., Stadnyk V. Yo., Salapak V. M. (2023). On the low-temperature isotro­pic point in Rb2SO4 crystals. Low temperature Physics, 49(10), 1163–1169.
  22. Stadnyk V., Matviishyn I., Ftomyn N., Vyshnevskyi V., Baliga V., Shtuka O. (2024). The photoelasticity of rhombic syngony crystals. Electronics and information technologies, 28, 157–167.
  23. Narasimhampurty T. S. Photoelastic and Electro-Optic Properties of Crystals. New York, Springer, 1981, 544 p.
  24. Rudysh M. Ya., Andriyevsky B. V., Shchepanskyi P. A. et al. (2025). Optical refractive proper­ties and phonon spectra of Na2SO4 single crystal. Optical Materials, 166, 117228(10).




DOI: http://dx.doi.org/10.30970/eli.30.14

Refbacks

  • There are currently no refbacks.