Electrooptic probing of MMIC devices with a semiconductor laser using a novel method for phase referencing

Measurements were made of both the phase and amplitude frequency response of GaAs MMICs (monolithic microwave integrated circuits) over a range of 2 to 18 GHz using electrooptic sampling with a gain-switched semiconductor laser. A novel phase-referencing technique allows accurate frequency scans of the phase response by eliminating problems associated with phase changes between the synthesizers driving the circuit and the laser. Using coated optics and differential detection, a voltage resolution of 0.5 mV/ square root Hz, within 4 dB of the shot-noise limit, has been achieved. >