Picosecond Voltage Pulses

Electronic devices operate at increasingly higher speeds, involving electrical transients on the picosecond time scale. To test these devices, voltage pulses of only a few picosecond duration are required as ultrashort trigger signals. At PTB, voltage pulses of 1,4ps width can now be generated with semiconductor switches driven by femtosecond laser pulses.

Picosecond voltage pulses are generated in microstructures which are lithographically produced from semiconductor thin films. In these photoconductive switches, a semiconducting gap with a typical width of 10µm is formed which can be electrically biased. If the semiconducting gap is illuminated by 100fs laser pulses, free charge carriers are generated and an electrical current begins to flow. The use of special semiconductor materials with charge carrier lifetimes of only a few picoseconds ensures that the current rapidly decreases, giving rise to the generation of ultrashort voltage pulses. The temporal shape of the voltage pulses is measured with sampling techniques employing also femtosecond laser pulses.

Up to now, PTB has succeeded in generating voltage pulses with a full width at half maximum of 1,4ps and a rise time of 1,0ps. As a first application, the picosecond voltage pulses will be used to calibrate the time response of 50GHz sampling oscilloscopes which become increasingly important for the characterisation of today´s high-speed electronic circuits.

For further information please contact U. Siegner,
fax: (+49 531) 592-42 72, e-mail: uwe.siegner@ptb.de