Investigation of Coupling Mechanism between Erbium (Er³⁺) and Ytterbium (Yb³⁺) in Alumina (A1₂O₃) Host

Abstract

Plasma-enhanced CVD (PECVD) deposited alumina (A1₂O₃) thin films and single sapphire crystals were co-doped with both erbium and ytterbium using ion implantation. Yb³⁺ and Er³⁺ concentrations ranged from 2.4At% to 8At% and from 0.4At% to 0.8At%, respectively. The samples show relatively strong, broad, room-temperature photoluminescence (PL) at λ=1.53µm corresponding to the intra-4f transitions between the ⁴I_13/2 (first excited) and the ⁴I_15/2 (ground) state of Er³⁺. The full width at half maximum (FWHM) of the emission spectrum is as high as 67nm for the A1₂O₃ thin films; for the sapphire crystals it is 45nm. The fluorescence lifetime of the samples has been measured to be as high as 4.2ms at 50mW laser pump power. The indirect pum** of erbium through the transfer of energy from ytterbium has been demonstrated and the PL peak intensity has been studied as a function of the Yb³⁺/Er³⁺ concentration ratio when the samples are pumped at 514nm and 850nm; the PL excitation spectrum (PL at 1.53gm as a function of pump wavelength) of an Er³⁺/Yb³⁺ co-implanted sample is also presented. Both the PL peak intensity at 1.53µm and the fluorescence lifetime have been studied as functions of annealing temperature. Luminescence spectra attributed to defects in the alumina matrix are presented for as-implanted samples and following thermal annealing.