Absorption cross section and signal enhancement in Er-doped Si nanocluster rib-loaded waveguides

Pump and probe experiments on Er3+ ions coupled to Si nanoclusters have been performed in rib-loaded waveguides to investigate optical amplification at 1.5 mu m. Rib-loaded waveguides were obtained by photolithographic and reactive ion etching of Er-doped silica layers containing Si nanoclusters grown by reactive sputtering. Insertion losses measurements in the infrared erbium absorption region allowed to gauge an Er3+ absorption cross section of about 5x10(-21) cm(2) at 1534 nm. Signal transmission under optical pumping at 1310 nm shows confined carrier absorption of the Si nanoclusters. Amplification experiments at 1535 nm evidence two pump power regimes: Losses due to confined carrier absorption in the Si nanoclusters at low pump powers and signal enhancement at high pump powers. For strong optical pumping, signal enhancement of about 1.2 dB/cm was obtained