Optical spectroscopy of Pr3+-doped γ-BiB3O6 crystals

Abstract Single crystals of Pr 3+ -doped γ-BiB 3 O 6 of optical quality were grown. Band gap is 4.16 eV at 80 K, which differs only slightly from that for undoped samples. Pr concentration is 2 × 10 20 cm −3 and the dopant is distributed uniformly along the crystal. Absorption cross-section for Pr 3+ was estimated to be ∼1 × 10 −20 cm 2 . At X-ray and UV, band-to-band excitation the Pr:γ-BiB 3 O 6 crystals demonstrate an intense emission in the 450 nm broad band, which is related mainly to recombination of self-trapped excitons (STE). A part of energy is transferred radiatively to Pr 3+ ions. The STE emission quenches as temperature increases to 250 K with simultaneous decrease of the decay time from 11 μs to 17 ns. Intensity and decay time of the Pr 3+ intracenter luminescence with τ ∼ 50 μs at 450 nm excitation do not depend on temperature. Intensity of thermoluminescence in the 150–400 K range quenches 2 orders at Pr doping, and parameters of the traps were estimated. As a result of relatively narrow band gap in γ-BiB 3 O 6 :Pr 3+ , there is no cascade luminescence typical of many wide-band-gap matrices.