Pump-probe experiments at 1.54 μm on silicon-rich silicon oxide waveguides

Optical pump-probe measurements were performed on slab waveguides containing excess silicon in the form of nanoclusters or nanocrystals and erbium. The measurements were performed by prism coupling a 1.54 mu m probe beam into a waveguide formed by silicon-rich oxide and monitoring its intensity and temporal response as the waveguide was optically pumped from above with a chopped 477 nm excitation source. Induced absorption (losses) of the 1.54 mu m probe beam in erbium-doped and undoped silicon-rich silicon oxide waveguides was observed in all cases. For the samples containing only well-defined nanocrystals, a fast (similar to 60 mu s) induced absorption component associated with free carriers within the silicon nanocrystals is reported, while for samples containing defective nanocrystals or nanoclusters, a much slower (> 10 min) component is observed. The free carrier absorption is shown to be reduced by delaying the probe beam relative to the pump beam in cases where it dominates. (c) 2006 American Institute of Physics.