NOVEL LASER GAIN MEDIA BASED ON CR3-DOPED MIXED BORATES RX(3)(BO3)(4)()

This letter discusses the optical properties of Cr3+ ions in mixed ber ate crystals with the formula RX(3)(BO3)(4), where R(3+)=Y3+ or Gd3+ a nd X(3+)=Al3+ or Sc3+. Measurements of the optical absorption spectra have been used to estimate the crystal field strength Dq and the Racah parameters B and C. These quantities confirm that in YAl3(BO3)(4)(YAB ) and GdAl3(BO3)(4)(GABCr3+ ions occupy strong crystal field sites [E( (2)E)<E(T-4(2))], whereas in YSc3(BO3)(4)(YSB) and CdSc3(BO3)(4)(GSB) the Cr3+ ions occupy weak field sites [E(T-4(2))<E((2)E)]. The consequ ence is that the fluorescence spectrum of Cr3+:YAB and GAB reveals the sharp R lines at low temperature and R lines plus broadband at 300 K. Both CP3+:YSB and GSB emit into the broadband T-4(2)-->(4)A(2) transi tion at all temperatures. The potential of these materials as laser ga in media is discussed. (C) 1995 American Institute of Physics.