Optical properties of amorphous, erbium-doped yttrium alumino-borate thin films

In this paper, we report on the optical characterizations of erbium-doped yttrium alumino-borate glassy thin films prepared by the polymeric precursor and sol–gel routes and the spin-coating technique. High quality planar waveguides were produced by a multilayer processing of Y1−xErxAl3(BO3)4 compositions with x = 0.02, 0.05, 0.10, 0.30, and 0.50. Their optical properties were investigated using transmission, photoluminescence, and m-lines spectroscopy, whereas high resolution scanning electron microscopy (HR-SEM) was applied to check film thickness and surface homogeneity. The refractive indices determined from transmission and m-lines spectroscopy are in good agreement just like the film thickness measured by HR-SEM and transmission spectroscopy. We observed low propagation losses, together with efficient photoluminescence emission for polymeric precursor thin films, involving low cost and environment friendly reactants.

► Glassy YAB hosts exhibiting high solubility for erbium ions to miniaturize the optical amplifiers. ► We measured and calculated some parameters as refractive index, thickness, loss, and PL emission. ► The erbium concentration, x, affects the refractive index with minimum values around x = 0.05–0.10. ► The x = 0.10 composition seems to be the most promising waveguide due to a low propagation loss.