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.
A study on the dynamics of gain spectral hole burning (GSHB) in a silica-based erbium-doped fiber amplifier at 77 K was performed. When a saturation signal was input into an Er3+-doped fiber, a multigain spectral hole structure that consisted of nine gain spectral holes, was observed in the wavelength region from 1510 to 1640 nm at 77 K. As for the Er3+ ion concentration dependence of these gain spectral holes, the depth of the gain spectral hole at around 1530 nm was found to become shallower in the silica-based erbium-doped fiber that had higher Er3+ ion content. This Er3+ ion concentration dependence of the gain spectral hole depth suggests that the contribution of the energy-transfer interaction between Er3+ ions excited to the Stark levels within the ^4 I_13/2 manifold plays an important role in the gain spectral hole formation at 77 K. As far as we know, this is the first report of the Er3+ ion concentration effect on the GSHB in the Er3+-doped fiber. The dynamics of GSHB is discussed in relation to the effect of energy transfer between Er3+ ions. In addition, the relation between gain spectral hole structure and the Stark energy structure of Er3+ ion is also discussed.