Static and Radio-frequency magnetic response of high Tc Superconducting Quantum Interference Filters made by ion irradiation

TL;DR

This paper investigates the RF and DC response of a high-temperature superconducting SQIF made by ion irradiation, demonstrating its potential for RF detection with linear response up to 150 MHz and modeling its behavior.

Contribution

It presents the fabrication and characterization of a high-temperature SQIF using ion irradiation, including a developed model for its RF response.

Findings

Detects RF signals up to 150 MHz

Maintains linear response over five decades of RF power

Shows minimal second-harmonic generation at optimal points

Abstract

Superconducting Quantum Interference Filters (SQIF) are promising devices for Radio- Frequency (RF) detection combining low noise, high sensitivity, large dynamic range and wide-band capabilities. Impressive progress have been made recently in the field, with SQIF based antennas and amplifiers showing interesting properties in the GHz range using the well-established Nb/AlOx technology. The possibility to extend these results to High Temperature Superconductors (HTS) is still open, and different techniques to fabricate HTS SQIFs are competing to make RF devices. We report on the DC and RF response of a High Temperature SQIF fabricated by the ion irradiation technique. It is made of 1000 Superconducting QUantum Interference Devices (SQUIDs) in series, with loop areas randomly distributed between 6 micron2 and 60 micron2. The DC transfer factor is around 450 V/T at optimal bias and temperature, and the maximum voltage swing around 2:5 mV . We show that such a SQIF detects RF signals up to 150 MHz. It presents linear characteristics for RF power spanning more than five decades, and non-linearities develop beyond PRF = -35 dBm in our set-up configuration. Second-harmonic generation has been shown to be minimum at the functioning point in the whole range of frequencies. A model has been developed which captures the essential features of the SQIF RF response.