Abstract: In this study, large size and high quality alexandrite (Cr³⁺∶BeAl₂O₄) crystals were grown by induction heating Czochralski method combined with automatic diameter control technology. The obtained crystal diameter size reaches 70 mm, the cylinder length reaches 140 mm, and its weight exceeds 2 800 g. Irradiated with a cold light source, there are bubbles in the center area of 10~15 mm. No scattered particles are found in the 8 mm×130 mm crystal rod under the irradiation of a 5 mW green laser. The wavefront distortion is 0.3λ@632.8 nm measured by a Zygo laser interferometer. The Cr³⁺ doping concentrations were measured by inductively coupled plasma atomic emission spectrometry. The axial molar concentration gradients are 0.5×10^-4~1.9×10^-4 cm^-1. The absorption spectra of the alexandrine crystals with different Cr³⁺ doping concentrations at room temperature were measured by Perkin Elmer Lambda-950 UV-Vis near-infrared spectrophotometer and the absorption coefficients were calculated. These results provide important basic data for the application of alexandrite crystals.

Key words: alexandrite(Cr³⁺∶BeAl₂O₄) crystal, Czochralski method, automatic diameter control technology, wavefront distortion, concentration gradient, absorption coefficient