Abstract

EuAlO₃ and GdAlO₃, Ti doped, have been grown by laser-heated pedestal growth as potential visible/near IR lasers. The absorption spectrum of EuAlO₃:Ti shows a strong, very broad absorption band in the visible and near infrared which is not consistent with that expected for Ti³⁺ in an octahedral field, or with intraionic transitions in other charge states of Ti. Its strength is indicative of a charge transfer transition. In addition, a strong ultraviolet band is evident above the absorption edge of undoped EuAlO₃. Both bands are attributed to Eu³⁺ + Ti³⁺ → Eu²⁺ + Ti⁴⁺ charge transfer transitions. The absorption spectrum of GdAlO₃:Ti in the visible region is consistent with Ti³⁺. The fluorescence band position at 610 nm and its room temperature lifetime of ~5 µs are consistent with a transition from the lower ²e_g state to the ²t_2g state. The 9×10¹³-Hz fluorescence bandwidth and estimated 36% quantum efficiency imply a peak stimulated emission cross section of ≃4×10^–20 cm². This cross section is smaller than that in Ti:Al₂O₃ and comparable with that of typical Cr³⁺ based laser materials. The absence of the charge transfer transitions in the spectra of GdAlO₃:Ti is due to the third ionization potential of Gd being ~4 eV smaller than that of Eu. This should shift the charge transfer absorption well into the ultraviolet.

© 1989 Optical Society of America