Superconducting Photosensitive Interfaces for Triggering RSFQ Circuits

• Published in: IEEE transactions on applied superconductivity 2007-06, Vol.17 (2), p.530-533
• Main Authors: Febvre, P., Toepfer, H., Ortlepp, T., Ebert, B., Badi, S., Uhlmann, F.H.
• Format: Article
• Language: English
• Subjects: Applied sciences; Bridge circuits; Bridges (electric); Circuit properties; Circuits; Design. Technologies. Operation analysis. Testing; Digital; Digital circuits; Electric bridges; Electric, optical and optoelectronic circuits; Electronic circuits; Electronics; Engineering Sciences; Exact sciences and technology; Femtosecond; Integrated circuits; Josephson junctions; Magnetic devices; Micro and nanotechnologies; Microelectronics; Microwave circuits; Microwaves; Optical films; Optical pulses; optoelectronic device; Pulse circuits; Pulsed lasers; RSFQ; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; single-flux-quantum logic; Superconducting devices; Superconducting films; Superconducting microwave devices; superconducting photoswitch; Superconductivity; Superconductors; Ultrafast optics
• ISSN: 1051-8223; 1558-2515
• DOI: 10.1109/TASC.2007.898682

Superconductive rapid single-flux-quantum (RSFQ) circuits are able to work in a digital mode with clock frequencies of tens to hundreds of GHz. They rely on shunted Josephson junctions assembled with thin films inductors. To date, there is no on-the-shelf instrumentation apparatus which allows to directly verify the digital operation of such circuits in the 100 GHz range and above. Nevertheless, it is of importance of being able to sample the output of RSFQ circuits, and RSFQ pulses themselves, in a time-resolved manner at ultrafast speed, in order to get direct information about the RSFQ circuit behavior and for some specific applications. At this stage, we want to prove that RSFQ circuits can be correctly triggered through optical means, i.e. with a femtosecond Ti-Sa pulsed laser synchronized with a readout setup. Superconducting bridges of different dimensions, based on niobium films, have been designed to act as photoswitches. They have been included in a microwave custom-made circuit connected to a simple RSFQ processing circuit based on the 1 kA/cm 2 JeSEF RSFQ process of IPHT Jena [1]. The design of different geometries is presented, along with the expected electrical features of the bridges and RSFQ circuits. Preliminary experimental results are also given.