Characteristics of Antenna Arrays of Superconducting Point-Contact Josephson Junctions.

Michael A. Tarasov, Е. А. Степанцов, T. Lindström +3 more

Andrew Longacre

Pei Wang, Wenshuai Wang, Hongwei Gao +1 more

This paper describes an array of superconducting planar Josephson junctions (JJs) for terahertz emission. The JJs with bowtie antennae are fabricated with superconducting thin film deposited on the bicrystal dielectric substrate and connected in series by superconducting striplines. The dielectric substrate is regarded as a dielectric resonator to improve the electromagnetic coupling between the JJs for coherent terahertz emission. With the CST electromagnetic software, the S parameters, E-field distribution and farfield pattern of the JJ array are studied by adjusting the width of the bowtie antennae. The results show that standing waves are formed in the dielectric substrate around 420 GHz, which could contribute to the coherent terahertz emission of the superconducting oscillators.

Norio Fujimaki, Yoichi Okabes, Sogo Okamura

Abstract Several studies have been performed on fabrication of Josephson junction arrays to improve the voltage sensitivity and impedance matching of Josephson junctions to be used as high‐speed and high‐sensitivity detectors of microwaves and submillimeter‐waves. This paper proposes a method for arranging point‐contact Josephson junctions in a net structure and describes experimental results of detection. First, we measured the I‐V characteristic at super low temperature and found that the critical current can be adjusted from a few μA to a few mA by varying the contact pressure. Next, we obtained the equivalent circuit of this net‐structure array installed in an x‐band waveguide in such a way that the array is perpendicular to the wave traveling direction. The net‐structure array was treated as a uniform surface impedance and the series admittance due to the gap between the array and the waveguide wall was obtained by an extension of the analysis for a capacitive window. To compare the equivalent circuit parameters with measured values, we carried out an impedance measurement at room temperature. The results agreed well with theoretical values. Further, a preliminary experiment for a wideband detection was performed in the superconducting state and obtained detection voltages for 10‐GHz signals as well as HCN laser light of wavelength 337 μm.

Terrence D. Clark

J. Martens, A. Pance, K. Char +2 more

High temperature superconducting Josephson arrays were investigated as possible millimeter wave sources. A junction technology was selected and improved to the point where radiation, near 1 microwatt off-chip, was measured from a variety of 2-dimensional arrays in the 70-160 GHz range. The arrays were tunable and were successfully coupled to a number of antennas for broadband, tunable transmission. Antennas for a variety of specific applications were selected on the basis of bandwidth requirements, impedance levels, polarization, and the possibility of sufficient monolithic integration. The final part of the program was a study of potential subsystems that would utilize these arrays. Interchip communications transceivers were studied and interchip coupling was demonstrated using two antenna-coupled arrays. The most promising application may be a monolithic clock source, near 100 GHz, for communications and signal processing systems. Josephson arrays, mm-wave sources.