Eu-doped ZnO-HfO sub(2) hybrid nanocrystal-embedded low-loss glass-ceramic waveguides

We report on the sol-gel fabrication, using a dip-coating technique, of low-loss Eu-doped 70SiO sub(2) -&$(30-x)$; HfO sub(2)-xZnO (x = 2, 5, 7 and 10 mol%) ternary glass-ceramic planar waveguides. Transmission electron microscopy and grazing incident x-ray diffraction experiments confirm the controlled growth of hybrid nanocrystals with an average size of 3 nm-25 nm, composed of ZnO encapsulated by a thin layer of nanocrystalline HfO sub(2), with an increase of ZnO concentration from x = 2 mol% to 10 mol% in the SiO sub(2)-HfO sub(2) composite matrix. The effect of crystallization on the local environment of Eu ions, doped in the ZnO-HfO sub(2) hybrid nanocrystal-embedded glass-ceramic matrix, is studied using photoluminescence spectra, wherein an intense mixed-valence state (divalent as well as trivalent) emission of Eu ions is observed. The existence of Eu super(2+) and Eu super(3+) in the SiO sub(2)-HfO sub(2)-ZnO ternary matrix is confirmed by x-ray photoelectron spectroscopy. Importantly, the Eu&2+,3+}$; -doped ternary waveguides exhibit low propagation losses (0.3 plus or minus 0.2 dB cm super(-1) at 632.8 nm) and optical transparency in the visible region of the electromagnetic spectrum, which makes ZnO-HfO sub(2) nanocrystal-embedded SiO sub(2)-HfO sub(2)-ZnO waveguides a viable candidate for the development of on-chip, active, integrated optical devices.