Improved emission cross-section of erbium and demonstration of energy transfer in As2Se3 thin films

Abstract

Although chalcogenide glasses are the best materials for taking advantage of the lanthanides’ luminescence properties, their application as active media on integrated optical circuits has been hindered due to the low lanthanide solubility and the intricate fabrication techniques explored until now. In this work, we use the co-evaporation method to introduce metallic erbium into a chalcogenide glass host and deposit highly homogeneous thin films suitable for photonic components. The “out of equilibrium” process allows adding large amounts of the dopant without inducing phase segregation or glass devitrification and without the need for adding structural mediators, which usually reduce the rare earth elements’ luminescence efficiency. A detailed study on the fluorescence of the thin films demonstrates that an important process of energy transfer exists between the erbium ions and the glassy matrix that extends the possibilities of excitation sources to all the energies above the glass band gap. The short Er³⁺ decay times suggest that the peculiar coordination between Er–Se promotes a large distribution of erbium sites that vary slightly in energy. Moreover, the exceptional characteristics of the glassy matrix As₃₈Se₆₂ (high refractive index and lowest phonon energies, among others) resulted in the highest emission cross-sections reported to date (22 × 10⁻²¹ cm²). Our results demonstrate that this material could meet the high emission requirement in the short distances of integrated circuits by offering higher emissions, low phonon losses, and luminescence properties above silica glass.