Visualization of the nonlinear optical space-charge region of bulk thermally poled fused-silica glass.

We etched thermally poled fused-silica coverslips in 49% HF for 30 s transverse to the poling direction to reveal structural details of the nonlinear region. A peaked ridge below the anode surface, corresponding to a slower etch rate than that of the bulk SiO(2) , was located approximately 5 microm below the anode surface for a poling time of 30 s. The ridge moved deeper into the glass logarithmically with poling time. This trend is qualitatively consistent with a recent model for the formation of the space-charge region that includes injection of hydrogen ions at the anode surface.

Planar geometry thin-film all-optical programmable switch.

We describe an all-optical programmable switch that can perform logic gate functions. This switch consists of a planar geometry germanium-doped silica waveguide, a Q-switched and mode-locked Nd:YAG laser, and the means of coupling laser light into different waveguiding modes of the thin film at the fundamental and second-harmonic frequencies. By the application of the appropriate optical programming sequence, the film-generated second-harmonic light can be made to perform the functionalities of various gates. In particular, a single waveguide was optically programmed to perform the Or function and was then made to perform the And function with little change to the experimental arrangement.

Single-pass imaging through a thick dynamic distorter using four-wave mixing.

We have reconstructed images after a single pass through a thick, turbulent aberrator. The reconstructed image's resolution was independent of the presence, severity, and length of a hot-air aberrator (at least 50 times the collecting optics' depth of field). The slowly responding four-wave mixing medium, fluorescein-doped boric acid glass, averaged out rapidly varying intensity apodizations, which would otherwise degrade the reconstructed image quality.

Effects of thick aberrators in one-way imaging schemes.

The ability of one-way imaging schemes to correct for the effects of thick aberrators is examined. These schemes correct an image for the influence of an intervening aberrator in a single pass. Single-pass image correction is observed for thick aberrators that change in times that are short compared with the nonlinear response time of the four-wave mixing material. Image degradation is observed for static aberrators.