Improved gain performance in Yb/sup 3+/-sensitized Er/sup 3+/-doped alumina (Al/sub 2/O/sub 3/) channel optical waveguide amplifiers

Small-signal amplification in short, Yb/sup 3+/-sensitized, Er/sup 3+/-doped alumina (Al/sub 2/O/sub 3/) channel optical waveguides with high Er/sup 3+/ concentrations is analyzed. Taking into account uniform up conversion, excited state absorption (ESA) from the Er/sup 3+/ metastable level (/sup 4/I/sub 13/2/), and Yb/sup 3+//spl rarr/Er/sup 3+/ energy transfer by cross relaxation, the obtainable gain improvements compared to Yb/sup 3+/-free Er/sup 3+/-doped Al/sub 2/O/sub 3/ optical waveguides are investigated. The amplifier model is based on propagation and population rate equations and is solved numerically by combining finite elements and the Runge-Kutta algorithm. The analysis predicts that 5-cm long Yb/sup 3+//Er/sup 3+/ co-doped Al/sub 2/O/sub 3/ waveguides show 13-dB net signal gain for 100 mW pump power at /spl lambda//sub p/=980 nm.