Stimulated emission from alexandrite (BeAl 2 O 4 :Cr 3+ )

A new laser material — alexandrite (BeAl 2 O 4 :Cr 3+ ) — was investigated. Alexandrite crystals were grown from a molten mixture of BeO and Al 2 O 3 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 R 1 line was observed at liquid nitrogen temperature. The stimulated emission wavelength was within the range 679.86–680.33 nm.