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IEEE Transactions on Applied Superconductivity

Subharmonic locking in Josephson junctions

Matteo Cirillo, Vittorio Merlo, Dag Winkler, Norbert Thyssen

Published Jun 1, 1999• 1 citation
Publisher

Abstract

We have designed and tested a coplanar waveguide configuration which allows for coupling and detection of microwave radiation to planar and stacked Josephson junctions structures. The design is particularly versatile for experiments such as phase-locking of Josephson oscillations to external signals and detection of low frequency components in the waveform of a pumped junction. Using this design we have measured subharmonic phase-locking in long Josephson junctions and performed a first quantitative check of the existing theoretical models.

DOI
10.1109/77.783842

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We have designed and tested a coplanar waveguide configuration which allows for coupling and detection of microwave radiation to planar and stacked Josephson junctions structures. The design is particularly versatile for experiments such as phase-locking of Josephson oscillations to external signals and detection of low frequency components in the waveform of a pumped junction. Using this design we have measured subharmonic phase-locking in long Josephson junctions and performed a first quantitative check of the existing theoretical models.
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Experiments are reported on a new geometry designed to couple long Josephson junction fluxon oscillators to a resonant cavity. The junctions were made with a niobium-aluminum oxide-niobium trilayer process with a critical-current density of around 1000 A/cm2. Various numbers of such junctions were incorporated directly as part of a coplanar strip half-wave resonator, with fundamental mode of about 34 GHz. Both the current density and oscillation frequency are higher than in previous experiments. Evidence for phase locking of multiple junctions is presented.
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