ELECTRICAL SINGLE-PULSE OPTOELECTRONIC SAMPLING OF X-RAY PHOTODETECTOR SIGNALS

A 100 gate optoelectronic sampler is used to measure the output electr ical signal provided by an ultrafast detector. The detector electrical pulse lasts from 20 ps to 100 ps (full width at half maximum) and is sampled every 3.5 ps. The total record length is 350 ps. Gate switches are made of thin CdTe films deposited by molecular beam epitaxy at lo w temperature on a sapphire substrate. Such a layer presents a carrier sweepout time of 1 ps, or less. Gate switches are turned on by a 350 fs laser pulse and the collected charges are stored in capacitors. Fou r 32-channel scanners are connected to a 4 x 1 video multiplexer to bu ild up a video signal of the 100 gates. The bandwidth of the propagati on line, namely 18 GHz, determines the bandwidth of the optoelectronic sampler. With a further realization this bandwidth will be increased to 35 GHz.