GENERATION AND PROPAGATION OF SUBPICOSECOND PULSES IN A PHOTOCONDUCTIVE GAAS SWITCH INTEGRATED ONTO A GOLD YBA2CU3OX COPLANAR TRANSMISSION-LINE STRUCTURE/

We present a new type of photoconductive GaAs switch, which can be int egrated directly onto an already existing high-T-c circuit. Our test c ircuit consists of two coupled coplanar transmission lines made of gol d on top of a YBa2Cu3Ox layer grown on a MgO substrate. When the photo conductive switch is irradiated with femtosecond laser pulses, subpico second (0.4 ps) electric pulses are created. These pulses are capable of propagating more that 1 mm along the transmission Line. The pulses were detected with a photoconductive sampling technique, and results a re presented at both room temperature and al: 81 K. The photoconductiv e switch is useful both as an optical trigger generating pulses and in the sampling system detecting the pulses, This switch can be used to characterize high-T, circuits e.g. SFQ logic in the subpicosecond time domain.