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We report on an experimental and theoretical study of the high-frequency mixing properties of ion-irradiated YBa 2 Cu 3 O 7 Josephson junctions embedded in THz antennas. We investigated the influence of the local oscillator power and frequency on the device performances. The experimental data are compared with theoretical predictions of the general three-port model for mixers in which the junction is described by the resistively shunted junction model. A good agreement is obtained for the conversion efficiency in different frequency ranges, spanning above and below the characteristic frequencies f c of the junctions. V C 2014 AIP Publishing LLC.

There is universal agreement between the United Nations and governments from the richest to the poorest nations that humanity faces unprecedented global challenges relating to sustainable energy, clean water, low-emission transportation, coping with climate change and natural disasters, and reclaiming use of land. We have invited researchers from a range of eclectic research areas to provide a Roadmap of how superconducting technologies could address these major challenges confronting humanity.Superconductivity has, over the century since its discovery by Kamerlingh Onnes in 1911, promised to provide solutions to many challenges. So far, most superconducting technologies are esoteric systems that are used in laboratories and hospitals. Large science projects have long appreciated the ability of superconductivity to efficiently create high magnetic fields that are otherwise very costly to achieve with ordinary materials. The most successful applications outside of large science are high-field magnets for magnetic resonance imaging, laboratory

Abstract-This work presents the results of the synthesis of a lightweight inexpensive reconfigurable planar array antenna. The antenna structure is based on four circular patches. The sources points and some discontinuities on the patches can be electronically reconfigured by means of radio-frequency (RF) switches in order to modify the radiation pattern. In particular, the main lobe could be steered towards a desired direction to obtain an optimal management of wireless resources. An experimental prototype has been realized and tested. Numerical and experimental results are reported and compared to assess the reconfigurable capabilities of the proposed antenna prototype.

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We report on the high-frequency mixing properties of ion irradiated YBa2Cu3O7 Josephson junctions. The frequency range, spanning above and below the characteristic frequencies fc of the junctions, permits a clear observation of the transition between two mixing regimes. The experimental conversion gain was found to be in good agreement with the prediction of the three-port model. Finally, we discuss the potential of the junctions to build a Josephson mixer operating in the terahertz frequency range.

A new NbN multilayer technology has been developed on 3 inch diameter R-plane sapphire substrates, for combining on-chip fast RSFQ circuits with GHz bandwidth optical links. The circuits take advantage of two high quality (110) NbN layers sputtered epitaxially on sapphire at 600°C and selectively patterned: a 400 nm thick layer (LL-250 nm at 6K) acts for the ground-plane and microbridge photodetectors are made of a 3.5-8 nm thick NbN epilayer with T, above 11 K. Innovative dielectrics formed of 10 nm thick MgO sputtered on top of 200 nm S O z layers are found to improve significantly the superconductivity of NbN junction electrode lines deposited below 300°C. Good quality, hysteretic 2 pm2 area, NbN/MgO/NbN junctions with high J, (up to 50 kA/cm2) are obtained with very large gap voltage (6.20 mV) and low sub-gap leakage current (V,,, > 15 mV) at 4.2 K. At 11 K such junctions are found self-shunted (J,-10 kA/cm2) with RJ, above 0.5 mV and with low J, spread in arrays. J, can be adjusted (reduced) without any detrimental effect on the junction quality or spread by annealing at 250°C.

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