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Abstract

A measurement system using electro-optic sampling and operative in the time domain characterizes devices over a bandwidth extending to upper microwave frequencies (e.g., 100 GHz). The device under test is mounted to or integrated on a substrate of electro-optic semiconductor material and is connected to transmisison and lines on the substrate. Sampling signals are electro-optically generated and propagate along the lines toward and away from the device under test, using a laser pulse beam incident on the substrate. The signals are electrically sampled by a laser pulse sampling beam which is responsive to the change in refractive index due to the signal at locations equidistant from the generation position. The waveform resulting from electro-optic sampling near the device under test corresponds to the sum of the signal incident upon the device and the signal reflected therefrom. The waveform resulting from electro-optic sampling at the location away from the device corresponds to the incident waveform. The waveforms are processed by subtracting the waveform corresponding to the incident signal from the waveform corresponding to the sum of the incident and reflected signal and Fourier transformed to derive the scattering parameters. The laser pulses are very short (in the picosecond or sub-picosecond range) and the transmission lines are uniform in their attenuation and dispersion characteristics, thereby enabling measurements to be made to extremely high microwave frequencies in the time domain and converted by Fourier transform to the frequency domain to determine the scattering parameters characterizing devices operative at such high frequencies.

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