Characterization of highly photorefractive and active silica-germania sputtered thin films

Abstract

We report on the characterization of highly photorefractive Er³⁺/Yb³⁺-doped silica-germania planar waveguides deposited by radio-frequency-magnetron-sputtering technique. Details of the deposition process in order to get low loss, single mode waveguides at 1550 nm are described. The material presents an intense absorption band in the UV region and irradiation by a KrF excimer laser source produces large positive refractive index changes, without the need of particular sensitization procedures. Dark line spectroscopy of the waveguide modes at 635 nm was performed to calculate the index change under UV exposure. Highly efficient photo-induced phase gratings have been fabricated in the slab waveguide. Waveguides spectroscopic properties of the ⁴I_13/2 <=> ⁴I_15/2 transition of the Er³⁺ ion, including lifetime and emission bandwidth, were examined. Photoluminescence excitation spectroscopy was also recorded to detect the Yb³⁺ to Er³⁺ energy transfer process.