La3+ and Er3+ co-doped Y2O3 transparent ceramics with a tunable refractive index and long coherence lifetime

La3+ is used as an index modifier to tune the refractive index of Er3+ doped Y2O3 transparent ceramics without reducing the coherence lifetime of Er3+ 4I13/2−4I15/2 transition. La3+ and Er3+ are incorporated into Y2O3 through a solution-phase nanoparticle synthesis and nanoparticles are sintered into transparent ceramics by hot isostatic press. The maximum La3+ doping concentration is about 10%, which increases the refractive index of Y2O3 by 0.009 (Δn/n = 0.48%). La3+ doping doesn't reduce Er3+ optical coherence lifetime. The homogeneous linewidth of Er3+(20 ppm) 4I13/2−4I15/2 transition in La3+ doped Y2O3 ceramics is about 10 kHz at 2 K and 0.65 T, which is close to the reported homogeneous linewidth in Er3+ doped Y2O3 ceramics and single crystals. Such La3+ Er3+ co-doped Y2O3 ceramics are proper materials to fabricate optical waveguides for quantum memory applications.