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IEEE Transactions on Applied Superconductivity

Constant-voltage resonant steps in underdamped Josephson-junction arrays and possibilities for optimal millimeter-wave power output

Branimir Vasilić, Paola Barbara, S. V. Shitov, Christopher J. Lobb

Published Mar 1, 2001• 3 citations
Publisher

Abstract

When a parallel external magnetic field is applied to underdamped Josephson-junction arrays, constant-voltage steps appear in their current-voltage characteristics. These steps correspond to different numbers of rows being switched to a new resonant state. If the number of switched rows is larger then a threshold number, the array radiates coherent microwave radiation. When the array is biased on a step, the number of radiating rows stays fixed and we can change the input power, P/sub DC/, by changing the bias current. We measure the output power, P/sub AC/ as a function of P/sub DC/. This dependence is linear at high powers with a slope /spl alpha/, while at low powers P/sub AC/ vanishes nonlinearly with P/sub DC/. For a given array, the slope /spl alpha/ is larger for steps that correspond to a larger number of switched rows. We present a systematic study of the dependence of the slope or on the size of the array and discuss its implications for obtaining optimal DC-to-AC conversion efficiency.

DOI
10.1109/77.919561

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When a parallel external magnetic field is applied to underdamped Josephson-junction arrays, constant-voltage steps appear in their current-voltage characteristics. These steps correspond to different numbers of rows being switched to a new resonant state. If the number of switched rows is larger then a threshold number, the array radiates coherent microwave radiation. When the array is biased on a step, the number of radiating rows stays fixed and we can change the input power, P/sub DC/, by changing the bias current. We measure the output power, P/sub AC/ as a function of P/sub DC/. This dependence is linear at high powers with a slope /spl alpha/, while at low powers P/sub AC/ vanishes nonlinearly with P/sub DC/. For a given array, the slope /spl alpha/ is larger for steps that correspond to a larger number of switched rows. We present a systematic study of the dependence of the slope or on the size of the array and discuss its implications for obtaining optimal DC-to-AC conversion efficiency.
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