Direct electro-optic sampling of transmission-line signals propagating on a GaAs substrate

The first picosecond electrooptic sampling measurement made directly in GaAs is reported, noting that this picosecond electrooptic probe is suitable for the noncontact electronic characterization of high-speed monolithic GaAs integrated circuits. A dual-wavelength picosecond optical source was used to simultaneously excite a GaAs photodiode and to measure the birefringence induced in a GaAs transmission line by the electrooptic effect. Using compressed picosecond pulses at 1.06 micron and the electrooptic effect inherent in GaAs, the fringing electric field of a microstrip transmission line deposited on the 100 face of a GaAs substrate was sampled. Frequency-doubled pulses at 0.532 micron were used to excite a Schottky photodiode which served as an electrical signal generator connected to the transmission line. The photoconductive extension of the transmission line was demonstrated, and possible uses for this property are suggested.