Sol-gel route to highly transparent (Ho_(0.05)Y_(0.95))_2Ti_2O_7 thin films for active optical components operating at 2 μm

摘要

We present a generic sol-gel route to the preparation of optically active nanocrystalline holmium-yttrium titanate (Ho0.5Y0.95)(2)Ti2O7 thin films, which exhibit a strong luminescence at 2 mu m. The films were prepared by the sol-gel process and thermally treated in a rapid thermal annealing furnace. The nano crystal size and optical properties were tailored by the processing temperature. The final film thickness was around 500 nm. X-ray diffraction analysis and Raman spectroscopy confirmed the high purity of the crystal phase of (Ho0.05Y0.95)(2)Ti2O7. The activation energy of crystal growth was 35.7 kJ mol(-1). The films had excellent structural and surface homogeneity causing their high transparency close to the theoretical limit of 93.39%. Refractive index of the film heat-treated at 1000 degrees C was around 1.98. The films exhibited strong emission at 2 mu m with a luminescence lifetime around 4.6 ms. Their properties together with processing feasibility make them promising materials for photonic applications. (C) 2018 Elsevier B.V. All rights reserved.