Co-precipitation of rare-earth-doped Y₂O₃ and MgO nanocomposites for mid-infrared solid-state lasers

Mid-infrared, solid-state laser materials face three main challenges: (1) need to dissipate heat generated in lasing; (2) luminescence quenching by multiphonon relaxation; and (3) trade-off in high thermal conductivity and small maximum phonon energy. We are tackling these challenges by synthesizing a ceramic nanocomposite in which multiple phases will be incorporated into the same structure. The undoped majority species, MgO, will be the main carrier of high thermal conductivity, and the minority species, Er:Y₂O₃, will have low maximum phonon energy. There is also an inherent challenge in attempting to make a translucent part from a mixture of two different materials with two different indexes of refraction. A simple, co-precipitation technique has been developed in which both components are synthesized in situ to obtain intimate mixing. These powders compare well to commercially available ceramics, including their erbium spectroscopy, even when mixed as a composite, and can be air-fired to ∼96% of theoretical density, yielding translucent parts. As the amount of Er:Y₂O₃ increases, the translucency decreases as the number of scattering sites start to coalesce into large patches. If the amount of Er:Y₂O₃ is sufficiently small and dispersed, the yttria grains will be pinned as individuals in a sea of MgO, leading to optimal translucency.