Stimulated emission from alexandrite (BeAl2O4:Cr3+)

A new laser material – alexandrite (BeAl₂O₄:Cr³⁺) – was investigated. Alexandrite crystals were grown from a molten mixture of BeO and Al₂O₃ taken in the stoichiometric ratio. The dimensions of the crystals reached 10×1×1 cm. The absorption spectrum at 300°K consisted of U and Y bands with maxima at 420 and 550–600 nm and of narrow lines B, R'_1,2,3, and B_1,2 at 465, 650–660, and 678.46–680.27 nm. Cooling to 77 °K shifted the R_1,2 lines by 8 Å toward shorter wavelengths. Stimulated emission of the R₁ line was observed at liquid nitrogen temperature. The stimulated emission wavelength was within the range 679.86–680.33 nm.