Picosecond optoelectronic switching in semiconductors using a partly covered gap

The design of an optoelectronic switching device capable of producing psec electric pulses for time-resolved photoconductivity determinations is reported. Nd-YAG laser pulses of 30-psec duration illuminate both the optoelectronic switch (a 50-ohm-impedance Cr-compensated GaAs sample with carrier lifetime about 700 psec and all but 1.5 mm of the gap covered with light-tight material) and a test switch (ion-beam-damaged hydrogenated SOS with recombination time 50 psec) at wavelengths 532 nm and either 480 or 600 nm, respectively. The results are analyzed using the correlation-function method and presented graphically, demonstrating the applicability of the switch.