Emission spectrum of Ti³⁺: Gd3Sc2Al3O12 garnet crystal

The photoluminescence spectrum of Ti³⁺-doped Gd₃Sc₂Al₃O₁₂ observed at 77 K and below consists of a series of zero-phonon lines with vibronic structure and a broad band spanning the wavelength range 650 to 1300 nm. By using time-resolved spectroscopy this spectrum has been shown to have overlapping features due to Cr³⁺ ions, present as ubiquitous impurities in most garnets, and Ti³⁺ ions, as the dominant active species in these crystals. The Cr³⁺ impurities are revealed by the zero-phonon lines at 689.2-690.4 nm with attendant phonon-assisted structure. The broadband with peak at 850 nm is identified with the multiphonon sideband of the ²E→²T₂ transition of Ti³⁺ in trigonally-distorted sites in Gd₃Sc₂Al₃O₁₂.