Transparent Er³⁺-Doped Y₂O₃ Ceramics with Long Optical Coherence Lifetime

Er³⁺-doped Y₂O₃ nanoparticles (NPs) are used to synthesize transparent ceramics by hot isostatic pressing. Two sizes of NPs are studied, and 40 nm NPs show better performance than 200 nm NPs in transparent ceramics syntheses. The axial optical transmission through millimeter thickness of the prepared ceramics is about 80% in the wavelength range of 1000-2000 nm. For a sample with 11.5 ppm Er³⁺, the inhomogeneous broadening of the ⁴I_15/2 to ⁴I_13/2 transition for the C₂ site is as low as 0.42 GHz (full width at half-maximum), and the homogeneous line width is 11.2 kHz at a temperature of 2.5 K and in a 0.65 T magnetic field. This indicates that a majority of Er³⁺ ions are sitting in sites with very low structural disorder.