Finite-element modeling of silica waveguide amplifiers with high erbium concentration

We report numerical analysis of planar and channel silica waveguide amplifiers with high erbium concentration. The numerical approach is based on the combined use of a full-vectorial finite-element method and the Runge-Kutta algorithm. It allows one to investigate real structures, accounting for both the active ions interactions by cross-relaxation and upconversion and the effects of waveguide geometry and refractive index profile. We show that, depending on input pump power and waveguide structure, ion-ion interactions affect the amplifier performance for high erbium concentrations. A three-dimensional waveguide designed for single-mode operation ensures higher pumping efficiency and lower noise characteristics than a two-dimensional one and seems to be the best candidate to overcome this drawback.>