IR luminescence decays and radiative lifetime of the level in Er3+ doped sol-gel TiO2 planar waveguides

Abstract The lifetime of the 4 I 13 2 level has been analyzed in erbium doped TiO 2 sol-gel planar waveguides as a function of the Er 3+ concentration and thermal treatments in the way of testing their potentially for optical amplification at 1.53 μm. Luminescence decay measurements were recorded by prism coupling of the 800 nm excitation laser beam into the waveguides and by detecting luminescence at 1.53 μm perpendicularly to the propagation plane. The observed increase of the lifetime with the annealing temperature has been related to the reduction in the hydroxyl group concentration evidenced by FTIR transmission spectra. Moreover, hydroxyl groups seem to play an important role in the strong shortening of decays by increasing Er 3+ concentration. The radiative lifetime of the 4 I 13 2 level has been estimated for erbium doped TiO 2 gel using the Judd-Ofelt framework. It compares well with the lifetimes of the lowest doped films annealed up to 650°C. This suggests that the 4 I 13 2 level radiative lifetime would almost be attained by means of annealing treatments in low doped waveguides.