Silicon photodiode for optical channel waveguides

An etched mesa silicon photodiode suitable for detecting light propagating in optical channel waveguides has been fabricated. The diode width of 7 μm was slightly less than that of the channel waveguide, thus minimizing junction capacitance and the effect of detection noise caused by unguided substrate light. The fabrication technique can be applied to produce on a single Si wafer multiple photodiodes electrically isolated from each other. Optical energy was coupled from (out-diffused)LiNbO3 channel waveguides into the photodiodes by means of evanescent field coupling.