The optical properties of ${\mathrm{C}}^{3+}$,${\mathrm{Nd}}^{3+}$, and ${\mathrm{Cr}}^3$:${\mathrm{Nd}}^{3+}$ ions in ${\mathrm{Ca}}_3$(GaNb${)}_2$${\mathrm{Ga}}_3$${\mathrm{O}}_{12}$ (CNGG) garnet have been investigated in the 4.2–550 K temperature range by using steady-state and time-resolved laser spectroscopy. The luminescence of trivalent chromium in a singly doped crystal shows a strong thermal quenching above room temperature, which can be analyzed on the basis of the quantum-mechanical single-configurational-coordinate model by using the Struck-Fonger method. Low-temperature absorption, excitation, and time-resolved luminescence spectra of the ${\mathrm{Nd}}^{3+}$ ion in a singly doped crystal show inhomogeneous broadening associated with the existence of different sites for ${\mathrm{Nd}}^{3+}$ ions. ${\mathrm{Cr}}^{3+}$-to-${\mathrm{Nd}}^{3+}$ radiative and nonradiative energy transfer has been demonstrated from the time-resolved emission spectra and the decrease of the ${\mathrm{Cr}}^{3+}$ fluorescence lifetime. The nonradiative ${\mathrm{Cr}}^{3+}$→${\mathrm{Nd}}^{3+}$ energy transfer is consistent with a dipole-dipole transfer process.

• Received 21 May 1993

DOI:https://doi.org/10.1103/PhysRevB.48.9279