Speed and effectiveness of windowless GaAs etalons as optical logic gates.

The effectiveness of surface recombination in speeding up the relaxation of a GaAs etalon is reported. Various thickness (1.5, 0.5, 0.3, 0.13microns) bulk-GaAs windowless samples were fabricated and tested as optical logic gates. Times for complete recovery of transmission lie between 400 and 30 ps. The response shows a roughly linear increase in speed as the sample thickness decreases, consistent with surface recombination being the dominant relaxation mechanism. A very fast cycle time of 70 ps is demonstrated using a 0.3-micron-thick windowless GaAs etalon as an all-optical logic device. Proton-bombarded samples show slower recovery and poorer contrast, and they require more gating energy.