Abstract

We report observations of a new optoelectronic mechanism to generate 180 mV, 350 fsec electrical pulses. For this mechanism to operate the laser excitation beam should be focused to a spot smaller than the separation between the two lines of a charged coplanar transmission line fabricated on an unimplanted silicon-on-sapphire (SOS) substrate, and should be positioned between the two lines partially illuminating the back side of the positive line. When these conditions were satisfied, we always observed a strong short pulse followed by a much weaker step function. For positive bias the signal strength was proportional to the bias voltage across the line. However, when the voltage polarity was changed the initial short pulse changed sign and was reduced in amplitude by 10 times. Increasing the focal spot size to completely fill the space between the two lines caused the short pulse to disappear and the expected step function for unimplanted material was obtained.

© 1988 Optical Society of America