Time evolution of the second-order nonlinear distribution of poled Infrasil samples during annealing experiments.

The spatial distribution of the second-order nonlinearity induced in thermally poled Infrasil silica samples is recorded after thermal annealing experiments. Two regimes have been studied: short and long poling durations. For short poling durations, the observations are in good agreement with a model where only one ion type recombines inside the depletion region. The nonlinear distribution and erasure observed for the other case are well explained by considering the addition of another positive-charged ion injected during the poling process. This second ion acts as a barrier during thermal annealing and reduces the mobility of the first one.

Heat scan: a simple technique to study gratings in fibers.

A simple and powerful technique to characterize gratings in fibers is described. It is based on scanning a small heating element along the fiber so as to disturb the phase relationship of the waves in a controlled way.