High speed optoelectronic mixer

An electronic mixer is decribed which utilizes an optoelectronic switch formed from a semi-insulating substrate of indium phosphide doped with a deep level impurity and disposed intermediate a microstrip transmission line. One conductor of the transmission line has a small gap in its metallization. Upon illumination of the gap by laser pulses from a laser source which are absorbed near the semiconductor surface, a photo-generated electron-hole plasma forms thereby providing a conducting path across the gap. An RF signal to be mixed with a LO signal is coupled to one side of the switch. The LO signal controls the Laser source. The output of the switch is therefore the product of the RF and LO signal.