Abstract

We have spectroscopically evaluated crystals of Nd³⁺:SrGdGa₃O₇(Nd³⁺:SGGM) to assess their potential for use as diode pumped solid-state laser materials. The single crystals were grown by the Czochralski method, and the samples were oriented using x-ray diffraction. The host, SrGdGa₃O₇ is a uniaxial crystal with tetragonal symmetry and is a subset of the melilite series of minerals. The samples studied here were doped with 2 at. % Nd³⁺ in the melt with respect to the Gd ion. Polarized absorption spectra reveal that the absorption coefficient for light having its E vector perpendicular to the c-axis, E_σ is larger than that for E parallel, E_π. The absorption coefficient for E_σ at 809 nm is 6.6 cm^-1, more than two times larger than that for E_π at the same wavelength. Similar differences in transition strengths have been measured in the emission spectra. Significant inhomogeneous broadening occurs in Nd:SGGM; the absorption linewidth at 809 nm is 10 nm FWHM. For a diode pumped solid-state laser this represents a significant improvement over the 1-nm FWHM linewidth in Nd: YAG at 810 nm. The fluorescence lifetime for the ⁴F_3/2 → ⁴I_11/2 transition at 1.06 µm is 245 µm in our Nd:SGGM crystals, which is 40% longer than lifetimes measured previously for Nd:SGGM crystals grown by the laser heated pedestal growth method,¹ and is comparable to the 230-µm lifetime for Nd:YAG.

© 1991 Optical Society of America