Properties of erbium and cerium co-doped TeO 2 thin films fabricated by reactive co-sputtering for waveguide amplifier

Abstract

Recently, we reported a high gain planar waveguide amplifier in Erbium doped TeO2 pumped at both 1480nm and 980nm [1, 2]. The performance of the amplifier pumped at 980nm was better than that at 1480nm as generally expected due to the non-resonant pumping. The high gain in a 980nm pumped Er:TeO2 waveguide amplifier led to lasing with only facet reflections. However, the performance of the 980nm pumped Er:TeO2 amplifier was still much lower than theoretical predictions due to the presence of ion-ion interactions and excited state absorption [2]. When pumped at 980nm, the Er ions are excited to the 4I11/2 state, and then in silica for example, rapidly decay nonradiatively to the 4I13/2 level. Because the decay life time from the 4I11/2 to the 4I13/2 level is relatively long in TeO2 on account of its much lower low phonon energy, there is a population build up at the 4I11/2 level and excited state absorption from the 4I11/2 to the 4F7/2 level occurs because of the resonance with the pump. This significantly reduces the pumping efficiency of the desired 1550nm transition. To reduce this un-desirable effect, the population at the 4I11/2 level needs to be minimized. There have been a number of reports of using Ce as co-dopant with Er in fibres and bulk glasses to quench the decay from 4I11/2 to 4I13/2 [3, 4]. However melt quenched glasses are very different to non-equilibrium formed thin films and it is not a priori obvious that this will work in a thin film due to the different glass structure. Show more