Ultrafast, integrable, optics-based interface between superconducting and room-temperature electronics

An ultrafast optical interface between superconducting and room-temperature electronics is proposed to take full advantage of high-speed superconducting circuits. We report on the computed and experimental studies of an optical receiving and modulating system that is compatible in processing with the prevailing integrated-superconducting-circuit technology. Planar interdigitated Nb/Si/Nb metal-semiconductor-metal (MSM) photodiodes are demonstrated as optical receivers with resolvable bit-rate as high as 38 Gb/s, and the response of MSM diode was shaped to be a single-flux-quantum pulse to drive Josephson-junction-based circuits. A similar interdigitated structure on a silicon waveguide is proposed to be an ultrafast light-intensity modulator, with its operation based on carrier-density modulation of the optical index of refraction. This field-effect device has insignificant power dissipation, in addition to high speed. A sample modulator with 5-V bias is shown to have a modulation depth of 40% and a bandwidth over 70 GHz.>