Electrooptic sampling of a packaged high-speed GaAs integratedcircuit

The authors describe the use of electrooptic sampling to characterize the performance of a packaged 1.7-GHz GaAs planar integrated decision circuit. To study the packaged device, it was necessary for the optical probe beam to impinge on the circuit from the front (active) side. This geometry enabled effective evaluation of the circuit, in spite of reduced spatial resolution and voltage sensitivity compared to a backside probing geometry. Using a gain-switched InGaAsP laser source, waveforms have been measured in the D flip-flop within the circuit and propagation delays of about 25 ps in the input buffers. Apparent crosstalk has been measured when the probe is positioned between adjacent active circuit lines and it is found that this crosstalk depends sensitively on the position of the probe beam