AN OPTOELECTRONIC TESTING SYSTEM OF RAPID, SINGLE-FLUX QUANTUM CIRCUITS

We have generated picosecond voltage pulses on a superconducting micro strip line by using a metal-semiconductor-metal photodiode as an optoe lectronic switch. These pulses are fed into a two-Josephson-junction p ulse shaper to generate single-flux quantum (SFQ) pulses. Using a refl ective electro-optic sampling system, SFQ pulses are directly observed for the first time. This important demonstration of nonintrusively de tecting electrical signals from superconducting microstrip lines at th e level of rapid, single-flux quantum (RSFQ) circuits opens up a new w ay to test such circuits, on issues such as design verification, jitte r, and failure-mode testing. Further, me propose a variable-rate optoe lectronic clock for testing the functional speed of RSFQ logic circuit s, with an adjustable clock rate up to 38 Gb/s.