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International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz)

390–480 GHz photon-assisted tunneling steps generated by parallel Josephson tunnel junction arrays

Faouzi M. Boussaha, A. Féret, Christine Chaumont, L. Pelay, Michele . Batrung, B. Lecomte, Morvan C. Salez, David Bouville, Frédéric Dauplay, Jean-Michel Krieg, G. Beaudin, L. Lapierre

Published Sep 1, 2010• 0 citations
Publisher

Abstract

We report on the first direct detection of submillimeter waves emitted by small parallel tunnel junction arrays. The arrays made up of 10 and 20 Nb/Al-AlOx/Nb junctions of 6 μm2is integrated and coupled in RF to Nb/Al-AlOx/Nb twin junction-based detector by a microstrip/slotline transition. The detector's I-V curve exhibits clearly photonassisted steps when the array is biased on the corresponding Josephson resonance at 390 and 480 GHz. These results are of particular significance in the light of previous work done on this type of devices. The arrays are specially suited for applications such as clock for RSFQ electronics or as local oscillator for THz superconducting integrated receivers.

DOI
10.1109/icimw.2010.5612942

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IEEE Transactions on Applied Superconductivity•Jun 1, 1999•12 citations
We report on the first direct detection of submillimeter waves emitted by small parallel tunnel junction arrays. The arrays made up of 10 and 20 Nb/Al-AlOx/Nb junctions of 6 μm2is integrated and coupled in RF to Nb/Al-AlOx/Nb twin junction-based detector by a microstrip/slotline transition. The detector's I-V curve exhibits clearly photonassisted steps when the array is biased on the corresponding Josephson resonance at 390 and 480 GHz. These results are of particular significance in the light of previous work done on this type of devices. The arrays are specially suited for applications such as clock for RSFQ electronics or as local oscillator for THz superconducting integrated receivers.
We report on tunable submillimeter-wave radiation sources based on micrometer-sized superconducting tunnel junction arrays optimized within a bandwidth of 350-520 GHz. The arrays consist of 10, 20 and 40 Superconductor-Insulator- Superconductor (SIS) parallel-connected Nb/AlOx/Nb junctions embedded in superconducting microstrip lines. A SIS twin-junction is integrated along with each array to detect output signals. The pumped detector’s I-V characteristic exhibits clearly photon-assisted quasiparticule steps when the arrays are biased upon corresponding Josephson resonances ranging from 370 to 520 GHz.
We developed submillimeter superconducting oscillators using Josephson effects in the Nb-based superconductor-insulator-superconductor (SIS) parallel array. The radiation emitted from the array is detected using integrated SIS twin junctions. Despite the small junction number (N = 21), the (I-V ) characteristics of the detector clearly exhibit photon-assisted quasiparticle steps when the array is biased upon its Josephson resonances, ranging from 370 to 500 GHz. The array has a moderate current density (Jc≈= 6 kA/cm2) but provides an output power around 0.28 μW, which would be sufficient in achieving sensitive heterodyne reception. The impedance array can be matched easier to microwave circuits than the usual long Josephson junctions. Furthermore, the parallel array approach can be also extended up to about 1.4 THz using Nb-based SIS junctions.
We report heterodyne measurements of Josephson microwave radiation emitted by a parallel array of small superconductor-insulator-superconductor (SIS) junctions at submillimeter-wave frequencies. The array consists of five Nb/Al–AlOx/Nb junctions nonevenly distributed in a niobium superconducting stripline, and is optimized for rf coupling in the 450–640 GHz range. We observed Fiske-like resonant steps in its I-V curve in the presence of magnetic field. The device was placed in a waveguide mount, and its radiation was quasioptically coupled out of the cryostat, to a SIS-mixer spectrometer in the same frequency range, with a 4–8 GHz band for spectral analysis. We detected a coherent signal in the spectra when the array was biased on the first and third steps, respectively, at the first harmonic frequency of 242 GHz and at the fundamental frequency of 493 GHz, both being the Josephson frequencies associated with their dc voltages. This strongly suggests that this type of parallel arrays optimized for wideband rf coupling, though strongly discretized, hosts dynamic fluxon regimes similar to long Josephson junctions, which could find applications in superconducting digital electronics or integrated heterodyne submillimeter-wave receivers.
We investigated parallel arrays of superconducting Nb/AlOx/Nb tunnel junctions nonevenly distributed in a superconducting Nb/SiO/Nb microstrip transmission line. Such devices are discretized Josephson transmission lines (DJTLs) in which, from theory, magnetic flux quanta (“fluxons”) can travel as solitonic waves when a dc current bias and a dc magnetic field are applied. We observed a reproducible series of resonant branches in each device’s I−V curve, at Josephson submillimeter-wave frequencies (from 240 to 720 GHz) matching the resonances predicted using a transmission line analysis, where the loading of the N=5 junctions is fully taken into account. The nonperiodic distribution was optimized to provide rf matching over a large bandwidth (450–650 GHz typically), implying that the plasma resonance of junctions is inductively tuned out over a similar band by the array. A confirmation of this comes from the observation, at frequencies higher than the untuned junctions plasma frequency, of several Josephson phenomena reported in this article: Fiske-like resonances, phase-locking of the n=3 resonance to an external 600 GHz microwave source, rf-induced zero crossing, and resonances at fractional harmonics of the rf signal. These experimental results are all compatible with a fluxon-based resonances interpretation, as in the extensively studied long Josephson junctions yet at higher frequencies. As reported elsewhere, we could detect ∼500 GHz microwave radiation emitted by our devices in the n=1 and n=3 modes. In light of these unique properties, we propose nonuniform DJTLs as a promising type of Josephson device for submillimeter-wave oscillators and fast fluxon-based electronics.
Submillimeter-wave direct detectors employing niobium-based superconducting tunnel junctions(STJs) match the request of broadband spectral response and high sensitivity,and having capability of large format arrays. We aim to realize the fractional bandwidth of 10 percent(60 GHz) at 650 GHz.The broadband coupling was designed using 2 distributed junction(DJ) arrays,which were composed of six STJs connected in parallel by a superconducting microstrip line.By analyze the DJ arrays,we found N-resonance combination needs to connect N-set of twin-junctions with short inductances through(N—1)-long inductances,alternatively.And we got the experiment result at 4.2 K that the center frequency of the STJ is 655 GHz,bandwidth about 50GHz,and the sensitivity is 1A/ W.
We have developed resistively shunted tunnel junctions with a small parasitic inductance (/spl equiv/100 fH) to improve the high-frequency performance of Josephson array oscillators. Josephson array oscillators with 11 such junctions and Nb microstrip resonators were designed and fabricated to operate at 690 GHz. Shapiro steps induced by Josephson oscillation were clearly observed at the submillimeter frequency region. By comparing the step height with the numerical simulation, we estimated the power of the Josephson oscillator delivered to the load resistor to be about 10 /spl mu/W at 625 GHz. The linewidth of the Josephson array oscillator was also measured using an integrated receiver consisting of two Josephson array oscillators and an SIS mixer. The designed frequency of the receiver was set at 550 GHz. IF output power spectrum was observed when both the oscillators were biased at about 1.17 mV which corresponds to 566 GHz. The composite linewidth of Josephson oscillation was measured about 8 MHz at 4.2 K.