Waveguiding terbium-doped yttrium aluminum garnet coatings based on the sol–gel process

Multi-layer luminescent Y3Al5O12:Tb3+ coatings have been prepared by the sol–gel route from alkoxide precursors. Highly transparent and crack-free 700–800 nm thick films were produced by the dip-coating technique from sols stabilized with acetylacetone as a chelating agent. High-temperature X-ray diffraction analysis shows that the films start to crystallize at 850 °C. On the basis of atomic force and scanning electron microscopies, it has been observed to have uniform and smooth surfaces. Waveguiding properties have been demonstrated by m-lines spectroscopy giving refractive index values of transverse electric and magnetic modes very close each other and the same thickness for both modes. These properties have only been observed for amorphous films, crystallization entailing the vanishment of waveguiding properties. Xe-lamp induced emission spectra of Tb3+ ions were recorded from amorphous and crystallized dip-coated films respectively annealed at 400 °C and 1000 °C. Spectra reveal the characteristic green emission arising from the Tb3+ 5D4 manifold for both samples.