Ion irradiation damage in Er-doped silica probed by the Er3+ luminescence lifetime at 1.535 μm

Abstract

The effect of MeV ion irradiation damage on the luminescence lifetime of erbium‐doped silica glass films has been studied. The 10‐μm‐thick films were first implanted with 3.5 MeV Er at a fluence of 5×10¹⁵ cm⁻². When optically pumped at 488 nm, the films show a clear photoluminescence spectrum centered around 1.535 μm, corresponding to the ⁴I_13/2→⁴I_15/2 transition of Er³⁺(4f¹¹), with a luminescence lifetime of 5.5 ms. After thermal annealing at 900 °C, the lifetime increases to 14.1 ms. Radiation damage was then introduced in the annealed films using 1 MeV He, 3.5 MeV C, 5.5 MeV Si, or 8.5 MeV Ge ions. The lifetime is decreased by irradiation with fluences as low as 10¹¹ ions/cm² and continues to decrease with fluence until saturation occurs above ≊10¹⁴ ions/cm². The saturation lifetime is ion‐mass dependent and ranges from 6.6 to 8.5 ms. The lifetime changes are explained in terms of nonradiative energy transfer processes caused by irradiation‐induced defects in the silica. A model for lifetime changes as a function of ion fluence is derived, assuming an inverse relation between the nonradiative lifetime and the defect density. Fits to the data show that the defect generation rate is a sublinear function of the ion fluence. The ion damage effects are governed by the electronic component of the energy loss along the ion trajectories.