  Superconducting double-loop interferometers (bi-SQUIDs) have been introduced
to produce magnetic flux sensors specifically designed to exhibit ultra-highly
linear voltage response as a function of the magnetic flux. These devices are
very important for the quantum sensing and for signal processing of signals
oscillating at the radio-frequencies range of the electromagnetic spectrum.
Here, we report an Al double-loop bi-SQUIDs based on proximitized mesoscopic Cu
Josephson junctions. Such a scheme provides an alternative fabrication approach
to conventional tunnel junction-based interferometers, where the junction
characteristics and, consequently, the magnetic flux-to-voltage and magnetic
flux-to-critical current device response can be largely and easily tailored by
the geometry of the metallic weak-links. We discuss the performance of such
sensors by showing a full characterization of the device switching current and
voltage drop \textit{vs.} magnetic flux for temperatures of operation ranging
from 30 mK to $\sim 1$ K. The figure of merit of the transfer function and of
the total harmonic distortion are also discussed. The latter provides an
estimate of the linearity of the flux-to-voltage device response, which
obtained values as large as 45 dB. Such a result let us foresee a performance
already on pair with that achieved in conventional tunnel junction-based
bi-SQUIDs arrays composed of hundreds of interferometers.
