Narrow inhomogeneous and homogeneous optical linewidths in a rare earth doped transparent ceramic

Inhomogeneous and homogeneous linewidth are reported in a Eu³⁺ doped transparent Y₂O₃ ceramic for the ⁷F₀-⁵D₀ transition, using high-resolution coherent spectroscopy. The 8.7-GHz inhomogeneous linewidth is close to that of single crystals, as is the 59-kHz homogeneous linewidth at 3 K (T₂ $=$ 5.4 μs). The homogeneous linewidth exhibits a temperature dependence that is typical of a crystalline environment, and additional dephasing observed in the ceramic is attributed to magnetic impurities or defects introduced during the synthesis process. The absence of Eu³⁺segregation at the grain boundaries, evidenced through confocal microfluorescence, further indicates that the majority of Eu³⁺ions in the ceramic experience an environment comparable to a single crystal. The obtained results suggest that ceramic materials can be competitive with single crystals for applications in quantum information and spectral hole burning devices, beyond their current applications in lasers and scintillators.