Single crystal β -Ga 2 O 3 : Cr grown by floating zone technique and its optical properties

β -Ga 2 O 3 : Cr single crystals were grown by floating zone technique. Absorption spectra and fluorescence spectra were measured at room temperature. The values of field splitting parameter Dq and Racah parameter B were obtained by the peak values of absorption spectra. The value 10 Dq / B =23.14 manifests that in β -Ga 2 O 3 crystals Cr 3+ ions are influenced by low energy crystal field. After high temperature annealing in air, the Cr 3+ intrinsic emission was enhanced and the green luminescence disappeared. The strong and broad 691 nm emission was obtained at 420 nm excitation due to the electron transition occurred from 4 T 2 to 4 A 2 . The studies manifest that the β -Ga 2 O 3 crystals have the potential application for tunable laser.