Effect of Si-nc to ${\hbox {Er}}^{3+}$ Coupling Ratio in EDWAs Longitudinally Pumped by Visible Broad-Area Lasers

We present a finite element based model for Si-nc sensitized Er³⁺ doped waveguide amplifiers (EDWA), longitudinally pumped by a novel pumping scheme using broad-area visible lasers, which accurately describes the effect of the Si-nc to Er³⁺ coupling ratio on the amplifier performance. We show that by pumping the active material resonantly with the Er³⁺ absorption spectrum, the Si-nc sensitization is extremely beneficial even at relatively low fractions of Er³⁺ ions coupled to the nanoclusters. On the other hand, when the pump light is only directly absorbed by the Si-nc, more than 80% of the Er³⁺ ions should be coupled to the Si-nc in order to achieve significant net gain. In particular, numerical results based on realistic material parameters, point out that resonant multimode pumping at 660 nm provides significant benefits in terms of gain enhancement, with respect to standard EDWAs, even at low fractions of Er³⁺ ions coupled to the Si-nc (less than 50%). This feature suggests that further material optimization could lead to the realization of compact and cost-effective integrated amplifiers and lasers.