Voltage Response of Non-Uniform Arrays of Bi-SQUIDs
Multi-loop arrays of Josephson Junctions (JJ) with non-uniform area distributions, which are known as Superconducting Quantum Interference Filters (SQIF), are the most highly sensitive sensors of changes in applied magnetic field as well as the absolute magnitude of magnetic fields. The non-uniformity of the loop sizes allows the array to produce a unique collective voltage response that has a pronounced single peak with a large voltage swing around zero magnetic field. To obtain high linear dynamic range, which is critical for a wide variety of applications, the linearity of the slope of the anti-peak response must be improved. We propose a novel scheme for enhancing linearity—a new configuration combining the SQIF array concept with the recently introduced bi-SQUID configuration, in which each individual SQUID loop is made up of three JJs as oppose to using two JJs per loop in standard DC SQUIDs. We show, computationally, that the additional junction offers a viable linearization method for optimizing the voltage response and dynamic range of SQIF arrays. We have realized SQIF arrays based on bi-SQUID cells and present first experimental results.
KeywordsMagnetic Flux Voltage Output Critical Current Josephson Junction Total Harmonic Distortion
We gratefully acknowledge support from the Tactical SIGINT Technology Program N66001-08-D-0154. We also wish to acknowledge support from the Office of Naval Research (ONR), Code 30, ONR NREIP Internship Program, the SPAWAR internal research funding (S&T) program, SPAWAR SBIR contracts N00039-08-C-0024 and N66001-09-R-0073. O. M. and G. P. thank V. Kornev, I. Soloviev, N. Klenov, A. Sharafiev for useful discussion related to bi-SQUID designs, D. Kirichenko for useful design and test advices, S. Tolpygo, R. Hunt, J. Vivalda, D. Yohannes, D. Amparo for chips fabrication, V. Dotsenko for cryoprobe design and fabrication.
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