Anisotropy of thermo-optic properties of beryllium hexaaluminate crystal doped with chromium ions

We determined the thermo-optic coefficients of Cr3+-doped beryllium hexaaluminate crystal (Cr3+:BeAl6O10) for light polarizations E||Np, Nm, and Ng, and present the thermo-optic dispersion formulas for the principal thermo-optic coefficients of Cr3+:BeAl6O10. We also measured the linear thermal expansion coefficients for this crystal in the directions of optical indicatrix axes Np, Nm, and Ng. Finally, we modeled the thermo-optic dispersion data in accordance with theory, taking into account contributions both from the change of the electronic bandgap with temperature and from the volumetric thermal expansion coefficient.