Abstract: Cr∶Al₂O₃ crystals with different Cr³⁺ concentrations were prepared by optical floating zone method, and cylindrical Cr∶Al₂O₃ crystals with different diameters (2 mm to 13 mm) and lengths greater than 100 mm were prepared. The densities of powder rods, ceramic rods and crystals obtained at different stages of Cr∶Al₂O₃ crystal preparation are measured to be 0.928, 2.230 and 4.051 g/cm³, respectively. XRD patterns show that Cr∶Al₂O₃ crystal is α-Al₂O₃ phase. The transmission spectra show that the transmittance of Cr∶Al₂O₃ crystal in visible light non-characteristic absorption band is more than 80%. The absorption spectra and photoluminescence excitation (PLE) spectra (monitoring 669 nm light) show that there are strong absorption bands at 418 and 559 nm, corresponding to the transitions of Cr³⁺ from ⁴A₂ to ⁴T₁and from ⁴A₂ to ⁴T₂, respectively. Under the excitation of light with a wavelength of 559 nm, the photoluminescence (PL) spectra of Cr∶Al₂O₃ crystals show a strong emission peak at 669 nm. At low Cr³⁺ concentration, the intensities of the peaks increase with Cr³⁺ concentration increasing, and reach the maximum value in Cr_{0.006 0}Al_{1.994 0}O₃ crystal, and then decrease with the increase of Cr³⁺ concentration.

Key words: Cr∶Al₂O₃, optical floating zone method, optical property, transmission spectrum, absorption spectrum, photoluminescence excitation spectrum, photoluminescence spectrum