Potassium gadolinium tungstate crystals KGd(WO₄)₂ doped with rare earth ions are very attractive solid-state laser materials [1]. It was found that KGd(WO₄)₂ crystals activated with trivalent lanthanide Ln³⁺ ions show high efficiency for stimulated emission at low pumping energies under laser diode excitation [2]. The crystal structure, optical and spectroscopic properties of pure and many Ln³⁺ ions doped KGd(WO₄)₂ crystals have been already described [3]. However, it is still a little known on their elastic properties at hypersonic frequencies.

Investigated pure and holmium doped KGd(WO₄)₂ single crystals were obtained by means of the Top Seeded Solution Growth method from K₂W₂O₇ solvent [4].

The Brillouin spectra of KGd(WO₄)₂ : Ho³⁺ crystals were collected at room temperature for the [100], [010], [001], [110], [-110], [011], [0-11], [101] and [-101] acoustic phonons in 90^o and 180^o scattering geometries. Some additional configurations of measurements have been applied for refractive indices determination. Using the measured frequencies of the acoustic phonons propagating in the main crystallographic directions the velocities of the proper elastic waves have been calculated. For investigated KGd(WO₄)₂ : Ho³⁺ crystals the values of elastic constants C₂₂ C₄₄ C₆₆ and C₄₆ associated with the longitudinal and transverse acoustic phonons propagating along the a and b crystallographic axes and the direction perpendicular to ab plane have been calculated. We compared the obtained values of the elastic constants with the proper values of the elastic constants determined for KGd(WO₄)₂ crystals [5]. The obtained results show that the elastic properties of KGd(WO₄)₂ : Ho³⁺ crystals are affected by the doping by Ho³⁺ ions.

Acknowledgement

This work was financed by the Research Project: MNiI 1 PO3B 058 27.

[1] A. A. Kaminskii, A. F. Konstantinova, V. P. Orekhova, A. V. Burtashin, R. F. Klevtsova, A. A. Pavlyuk, Crystallography Reports, 46 (2001) 665 – 672.

[2] M. C. Pujol, M. Aguilό, F. Díaz, C. Zaldo, Optical Mater., 13 (1999) 33.

[3] M. C. Pujol, M. Rico, C. Zaldo, R. Sole, V. Nikolov, X. Solans, M. Aguilo, F. Díaz, Appl. Phys. B, 68 (1999) 187 – 197.

[4] A. Majchrowski, M. T. Borowiec, E Michalski, J. Cryst. Growth, 264 (2004)201.

[5] D. Kasprowicz, S. Mielcarek, A. Majchrowski, E. Michalski, M. Drozdowski, Cryst. Res. Technol., 41(2006)541.

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