Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

High-speed optoelectronic interfaces for RSFQ superconductive electronics

Siham Badi, Pascal Febvre, Hervé Eusèbe, Jean-François Roux, Jean‐Louis Coutaz, Arūnas Krotkus, Bjoern Ebert, H. Toepfer, Th. Ortlepp, F.H. Uhlmann, Jürgen Kunert, Ludwig Fritzsch, H.-G. Meyer

Published Aug 30, 2004• 0 citations
OpenAlex

Abstract

The main goal of this work is to evaluate theoretically and experimentally the properties of ultrafast opto-superconducting interfaces used to trigger superconducting digital RSFQ circuits externally and to read the outcoming signal from the rapid single-flux-quantum (RSFQ) circuits. To do this, optoelectronics sampling techniques based on a Ti-Sa femtosecond pulsed laser are used. In a first step, miscellaneous Josephson junction-based devices (series of junctions, SQUIDS, simple RSFQ circuits) have been measured to evaluate the properties of the superconductive devices. In particular, I-V curves and magnetic diffraction patterns curves have been obtained. Since the picosecond pulses carried by the RSFQ circuits are weak, of the order of 1 mV or less, the interfaces with the external world have to be carefully designed. Therefore, the potentialities of different photoconductive switches for ultrafast and sensitive detection of picosecond pulses emitted by superconducting digital circuits are evaluated. To do so, a study of the influence of different electrical parameters associated to the geometry of photoswitches electrodes deposited on LT-GaAs materials is performed. The electrical response of dc-biased photoswitches illuminated by femtosecond pulses from a pulsed 800 nm Ti-Sa laser has been calculated for different geometries of electrodes. Using electro-optical sampling techniques, the response of some photoswitches are currently being measured.

Related papers

Superconducting Photosensitive Interfaces for Triggering RSFQ Circuits

Pascal Febvre, Hannes Toepfer, Thomas Ortlepp +3 more

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/cm2JeSEF 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.

IEEE Transactions on Applied Superconductivity•Jun 1, 2007•1 citation

Superconductive Microwave Single-Flux-Quantum Digital Circuits and Corresponding Opto-Electronic Interfaces: On-Going Studies and First Experimental Results

Pascal Febvre, Siham Badi, Torsten Reich +2 more

Superconductive microwave rapid single-flux-quantum (RSFQ) digital circuits offer the possibility to digitally process signals in the frequency range of tens of GHz. An example of application to bring the advantages of this technology deals with digital SQUIDs, used for sensitive magnetometry with a broadband dynamics connected to a slew-rate in the GHz range. First recently obtained results of digital SQUID operation, based on Nb/Al-Al2O3/Nb shunted Josephson junctions, are presented in this article. In order to obtain the best performance of RSFQ circuits, and especially to push their speed at its limits, a precise diagnostic of such circuits is needed. We are developing a time-resolved diagnostic system based on sensitive photoconductive switches to sample the weak signals coming out of RSFQ circuits at cryogenic temperature. This system includes two different sorts of opto-RSFQ interfaces, based on superconducting and semiconducting materials, respectively. Some simulation results in the microwave range, along with measurements giving the potentialities of different photoswitches are presented.

•Jul 13, 2005•0 citations

An optoelectronic testing system of rapid, single-flux quantum circuits

M. Currie, Chia-Chi Wang, D. Jacobs-Perkins +2 more

We have generated picosecond voltage pulses on a superconducting microstrip line by using a metal-semiconductor-metal photodiode as an optoelectronic switch. These pulses are fed into a two-Josephson-junction pulse shaper to generate single-flux quantum (SFQ) pulses. Using a reflective electro-optic sampling system, SFQ pulses are directly observed for the first time. This important demonstration of nonintrusively detecting electrical signals from superconducting microstrip lines at the level of rapid, single-flux quantum (RSFQ) circuits opens up a new way to test such circuits, on issues such as design verification, jitter, and failure-mode testing. Further, we propose a variable-rate optoelectronic clock for testing the functional speed of RSFQ logic circuits, with an adjustable clock rate up to 38 Gb/s.>

IEEE Transactions on Applied Superconductivity•Jun 1, 1995•10 citations

Optoelectronic clocking system for testing RSFQ circuits up to 20 GHz

J.F. Buzacchelli, Hae-Seung Lee, Sotiris Alexandrou +2 more

Unlike coaxial cable, optical fiber has a bandwidth commensurate with the clock rates of even the fastest rapid single flux quantum (RSFQ) circuits. Employing this advantage, we have developed an optoelectronic clocking system, in which optical pulses from a picosecond laser are delivered via fiber to a superconducting chip, on which metal-semiconductor-metal (MSM) photodiodes generate fast electrical pulses with subpicosecond timing accuracy. An optical pulse splitter, constructed out of beamsplitters, mirrors, and half-wave plates, permits selection of pulse pattern and clock rate from 80.6 MHz up to 20.6 GHz. With a sampling oscilloscope, we have directly observed optical triggering of an RSFQ T flip-flop at frequencies up to 1.3 GHz with a variety of bit patterns. Optical triggering of a Josephson transmission line (JTL) at frequencies up to 20.6 GHz has been verified by precise measurement of the Josephson voltage; this result represents the highest clock rate ever reported for an optical interface for RSFQ circuits.

IEEE Transactions on Applied Superconductivity•Jun 1, 1997•22 citations

Subpicosecond dynamics of the switching process in Y-Ba-Cu-O Josephson junctions

Roman Adam, Roman Sobolewski, Marian Darula

We present comprehensive experimental and numerical studies of the subpicosecond switching dynamics of YBa2Cu3O7-x (YBCO) grain-boundary Josephson junctions, excited by single-picosecond electrical pulses. The test structures were patterned in 100-nm- thick YBCO films grown by pulsed laser deposition on (100) MgO bicrystal substrates. Each sample consisted of a coplanar strip (CPS) transmission line, a microbridge acting as the electrical pulse generator, and a single Josephson junction positioned between the CPS lines about 100 micrometer away from the bridge. The junctions were characterized by the nonhysteretic current-voltage characteristics with the characteristic voltage approximately equal to 2.0 mV at 20 K (temperature of our experiments). A train of 100- fs-wide optical pulses from a Ti:sapphire laser photo-excited the microbridge and generated 2-ps-wide electrical pulses, which were then applied to switch the junction. In addition to the input pulse, the junction was dc-biased at +0.7 Ic, -0.7 Ic, +1.5 Ic, -1.5 Ic, and zero-Ic, where Ic is junction critical current. Time-resolved dynamics of the junction response was studied with the help of our cryogenic electro-optic sampling system, which can be regarded as a sampling oscilloscope featuring < 200-fs time resolution and < 150-(mu) V voltage sensitivity. We obtained 0.7-ps-wide single-flux-quantum (SFQ) pulses generated as a result of the junction switching process. The measurements were compared to numerical computations based on the equivalent circuit containing a resistively shunted Josephson junction, and we have found a satisfactory agreement between our simulations and experimental data. We believe our findings provide experimental confirmation of the potential of YBCO Josephson gattes as building blocks of ultrafast (sub-THz) digital electronics.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Sep 6, 2000•3 citations

Ultrafast Superconducting Digital Circuits for Analysis and Processing of Microwave Signals

Pascal Febvre, Torsten Reich, Thomas Ortlepp +1 more

Rapid-Single-Flux-Quantum (RSFQ) digital circuits based on shunted Josephson junctions have been shown to be able to digitally process signals up to several hundreds GHz. The principle of operation is based on the generation, transport and processing of picosecond voltage pulses of 2.07 mV.ps quantized area, which corresponds to one quantum flux h/2e. Operation of RSFQ circuits can be performed with clock frequencies of the order of 20 to 50 GHz with present technology. We will present current developments and experimental results obtained so far, based on circuits developed in the JeSEF RSFQ process of IPHT Jena, using a 1 kA/cm2 shunted Nb/Al-AlOx/Nb junctions. Some particular potential applications for space will be emphasized

•May 1, 2006•0 citations
The main goal of this work is to evaluate theoretically and experimentally the properties of ultrafast opto-superconducting interfaces used to trigger superconducting digital RSFQ circuits externally and to read the outcoming signal from the rapid single-flux-quantum (RSFQ) circuits. To do this, optoelectronics sampling techniques based on a Ti-Sa femtosecond pulsed laser are used. In a first step, miscellaneous Josephson junction-based devices (series of junctions, SQUIDS, simple RSFQ circuits) have been measured to evaluate the properties of the superconductive devices. In particular, I-V curves and magnetic diffraction patterns curves have been obtained. Since the picosecond pulses carried by the RSFQ circuits are weak, of the order of 1 mV or less, the interfaces with the external world have to be carefully designed. Therefore, the potentialities of different photoconductive switches for ultrafast and sensitive detection of picosecond pulses emitted by superconducting digital circuits are evaluated. To do so, a study of the influence of different electrical parameters associated to the geometry of photoswitches electrodes deposited on LT-GaAs materials is performed. The electrical response of dc-biased photoswitches illuminated by femtosecond pulses from a pulsed 800 nm Ti-Sa laser has been calculated for different geometries of electrodes. Using electro-optical sampling techniques, the response of some photoswitches are currently being measured.
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/cm2JeSEF 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.
Superconductive microwave rapid single-flux-quantum (RSFQ) digital circuits offer the possibility to digitally process signals in the frequency range of tens of GHz. An example of application to bring the advantages of this technology deals with digital SQUIDs, used for sensitive magnetometry with a broadband dynamics connected to a slew-rate in the GHz range. First recently obtained results of digital SQUID operation, based on Nb/Al-Al2O3/Nb shunted Josephson junctions, are presented in this article. In order to obtain the best performance of RSFQ circuits, and especially to push their speed at its limits, a precise diagnostic of such circuits is needed. We are developing a time-resolved diagnostic system based on sensitive photoconductive switches to sample the weak signals coming out of RSFQ circuits at cryogenic temperature. This system includes two different sorts of opto-RSFQ interfaces, based on superconducting and semiconducting materials, respectively. Some simulation results in the microwave range, along with measurements giving the potentialities of different photoswitches are presented.
We have generated picosecond voltage pulses on a superconducting microstrip line by using a metal-semiconductor-metal photodiode as an optoelectronic switch. These pulses are fed into a two-Josephson-junction pulse shaper to generate single-flux quantum (SFQ) pulses. Using a reflective electro-optic sampling system, SFQ pulses are directly observed for the first time. This important demonstration of nonintrusively detecting electrical signals from superconducting microstrip lines at the level of rapid, single-flux quantum (RSFQ) circuits opens up a new way to test such circuits, on issues such as design verification, jitter, and failure-mode testing. Further, we propose a variable-rate optoelectronic clock for testing the functional speed of RSFQ logic circuits, with an adjustable clock rate up to 38 Gb/s.>
Unlike coaxial cable, optical fiber has a bandwidth commensurate with the clock rates of even the fastest rapid single flux quantum (RSFQ) circuits. Employing this advantage, we have developed an optoelectronic clocking system, in which optical pulses from a picosecond laser are delivered via fiber to a superconducting chip, on which metal-semiconductor-metal (MSM) photodiodes generate fast electrical pulses with subpicosecond timing accuracy. An optical pulse splitter, constructed out of beamsplitters, mirrors, and half-wave plates, permits selection of pulse pattern and clock rate from 80.6 MHz up to 20.6 GHz. With a sampling oscilloscope, we have directly observed optical triggering of an RSFQ T flip-flop at frequencies up to 1.3 GHz with a variety of bit patterns. Optical triggering of a Josephson transmission line (JTL) at frequencies up to 20.6 GHz has been verified by precise measurement of the Josephson voltage; this result represents the highest clock rate ever reported for an optical interface for RSFQ circuits.
We present comprehensive experimental and numerical studies of the subpicosecond switching dynamics of YBa2Cu3O7-x (YBCO) grain-boundary Josephson junctions, excited by single-picosecond electrical pulses. The test structures were patterned in 100-nm- thick YBCO films grown by pulsed laser deposition on (100) MgO bicrystal substrates. Each sample consisted of a coplanar strip (CPS) transmission line, a microbridge acting as the electrical pulse generator, and a single Josephson junction positioned between the CPS lines about 100 micrometer away from the bridge. The junctions were characterized by the nonhysteretic current-voltage characteristics with the characteristic voltage approximately equal to 2.0 mV at 20 K (temperature of our experiments). A train of 100- fs-wide optical pulses from a Ti:sapphire laser photo-excited the microbridge and generated 2-ps-wide electrical pulses, which were then applied to switch the junction. In addition to the input pulse, the junction was dc-biased at +0.7 Ic, -0.7 Ic, +1.5 Ic, -1.5 Ic, and zero-Ic, where Ic is junction critical current. Time-resolved dynamics of the junction response was studied with the help of our cryogenic electro-optic sampling system, which can be regarded as a sampling oscilloscope featuring < 200-fs time resolution and < 150-(mu) V voltage sensitivity. We obtained 0.7-ps-wide single-flux-quantum (SFQ) pulses generated as a result of the junction switching process. The measurements were compared to numerical computations based on the equivalent circuit containing a resistively shunted Josephson junction, and we have found a satisfactory agreement between our simulations and experimental data. We believe our findings provide experimental confirmation of the potential of YBCO Josephson gattes as building blocks of ultrafast (sub-THz) digital electronics.
Rapid-Single-Flux-Quantum (RSFQ) digital circuits based on shunted Josephson junctions have been shown to be able to digitally process signals up to several hundreds GHz. The principle of operation is based on the generation, transport and processing of picosecond voltage pulses of 2.07 mV.ps quantized area, which corresponds to one quantum flux h/2e. Operation of RSFQ circuits can be performed with clock frequencies of the order of 20 to 50 GHz with present technology. We will present current developments and experimental results obtained so far, based on circuits developed in the JeSEF RSFQ process of IPHT Jena, using a 1 kA/cm2 shunted Nb/Al-AlOx/Nb junctions. Some particular potential applications for space will be emphasized