Pulse response of a high power waveguide optoelectronic switch for track and hold operation

For an analog-to-digital converter (ADC), it is important to have precise sampling time control to avoid resolution degradation. At high sampling rates, this precise sampling time control becomes increasingly difficult to achieve. To relax the stringent timing requirement of an ADC quantizer, a track-and-hold (T&H) circuit is implemented in many ADC architectures. In this work, a high power, high speed waveguide integrated photodiode (WIP) is tested as an optoelectronic switch for the T&H function. The photodiode operates with light launched into a passive waveguide before being coupled into the absorber. Using a matching layer between the passive waveguide and the absorber, the absorption profile along the absorber waveguide is modified to give small peak absorption. This reduces the effect of the charge screening effect and also the heating effect, so that the saturation power of the photodiode can be increased. Pulse measurement of an optical WIP switch is presented. The results show the peak current reaches 50 mA and the rise time is approximately 18.2 ps. These results show this switch can potentially be used for clocking an electronic T&H circuit.