Abstract.Superconducting Quantum Interference Filters (SQIFs) are arrays of superconducting loops of different sizes including Josephson Junctions (JJ). For a random distribution of sizes, they present a non-periodic response to an applied magnetic field, with a large transfer function and a magnetic field sensitivity potentially improved with respect to that of a single SQUID. Such properties make SQIFs interesting devices arXiv:1603.07592v2 [cond-mat.supr-con] 1 Jun 2016High-Tc Superconducting Quantum Interference Filters (SQIFs) made by ion irradiation2 to detect the magnetic component of electromagnetic waves at microwave frequencies.We have used the highly scalable technique of ion irradiation to make SQUIDs and SQIFs based on commercial YBa 2 Cu 3 O 7 films, and studied their properties. Both display optimum performances as a function of temperature and bias current, that can be understood in the frame of numerical simulations that we developed. The role of asymmetries and dispersion in JJ characteristics (routinely found in High Tc Superconductors technologies) is also studied. We have found that both do not impede the existence of a SQIF effect but play a role on the emergence of the optimal point. We finally present results on SQIF made with 2000 SQUID in series, showing a transfer function dV /dB ∼ 1000V /T .

We have fabricated arrays of High-T c Superconducting Quantum Interference Devices (SQUIDs) with randomly distributed loop sizes as sensitive detectors for Radio-Frequency (RF) waves. These subwavelength size devices known as Superconducting Quantum Interference Filters (SQIFs) detect the magnetic component of the electromagnetic field. We used a scalable ion irradiation technique to pattern the circuits and engineer the Josephson junctions needed to make SQUIDs. Here we report on a 300 SQUIDs series array with loops area ranging from 6 to 60 µm 2 , folded in a meander line covering a 3.5 mm×120 µm substrate area, made out of a 150 nm thick YBa 2 Cu 3 O 7 (YBCO) film. Operating at a temperature T = 66 K in an un-shielded magnetic environment, under low DC bias current (I = 60 µA) and DC magnetic field (B = 3 µT), this SQIF can detect a magnetic field of a few pT at a frequency of 1.125 GHz, which corresponds to a sensitivity of a few hundreds of fT/ √ Hz, and shows linear response over 7 decades in RF power.This work is a promising approach for the realization of low dissipative sub-wavelength GHz magnetometers.

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 µm 2 and 60 µm 2 . The DC transfer factor is ∼ 450 V T −1 at optimal bias and temperature, and the maximum voltage swing ∼ 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 P RF = −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.

International audienceUsing the dielectric resonator method, we have investigated nonlinearities in the surface impedance Zs = Rs + jXs of YBa2Cu3O7 thin films at 10 GHz as function of the incident microwave power level and temperature. The use of a rutile dielectric resonator allows us to measure the precise temperature of the films. We conclusively show that the usually observed increase of the surface resistance of YBa2Cu3O7 thin film as function of microwave power is due to local heating