OPTICAL INPUT-OUTPUT INTERFACE SYSTEM FOR JOSEPHSON-JUNCTION INTEGRATED-CIRCUITS

An optical input/output interface system for a Josephson junction inte grated circuit is fabricated and tested. The system consists of a supe rconducting optical detector, a dc powered Josephson circuit, a dc pow ered Josephson high voltage circuit, a liquid-He-cooled semiconductor amplifier, and a liquid-He-cooled semiconductor laser. Features of the system are use of an ultrathin NbN film for the optical detector and adoption of the dc powered Josephson circuits for logic operation circ uits. Correct optical output signal is detected by a liquid-He-cooled semiconductor photodiode. The optical input/output interface has the a dvantage of low heat penetration and low crosstalk compared to the int erface using conventional coaxial lines. Moreover, dc powered Josephso n circuits have an advantage of low crosstalk from power supply lines compared to conventional Josephson circuits, which are driven by ac su pply current.