Accurate measurement of 1.5 μm lifetime of Er3+ in LiNbO3 crystals and waveguides

Abstract

Two optimized methods for accurately measuring the 1.5 μm lifetime of Er3+ in LiNbO3 crystals and waveguides are proposed. The first method, suitable for measurement of bulk material, was suggested by forming an annealed proton exchanged sandwich structure and fluorescence was collected through an adjustable aperture. This excitation collection scheme was used to investigate bulk Er-doped LiNbO3 crystals with eight different Er3+ doping levels, three different crystal thicknesses, and three different cut orientations. The 1.5 μm lifetime was investigated in three configurations: with both a sandwich and an aperture, with a sandwich but without an aperture, and without not only a sandwich but also without an aperture. In addition, the effect of the aperture was also studied. The second method, suitable for a waveguide structure, was proposed on the basis of transversely gathering the fluorescence aided by an outcoupling fiber. It was optimized by comparing three different fluorescence collection schemes. Using this method, the lifetimes of some Ti:Er:LiNbO3 strip waveguides were measured. In addition, the effect of radiation trapping on the polarized fluorescence spectrum was also investigated. The experimental results are discussed and summarized.