  It is a well known phenomenon in optics that spectroscopic resolution of a
diffraction grating is much better compared to an interference device having
just two slits, as in the Young's famous double-slit experiment. On the other
hand, it is well known that a classical superconducting quantum interference
device (SQUID) is analogous to the optical double-slit experiment. Here we
report experiments and present a model describing a superconducting analogue to
the diffraction grating, namely an array of superconducting islands positioned
on a topological insulator (TI) film Bi0.8Sb1.2Te3. In the limit of extremely
weak field, of the order of one vortex per the entire array, such devices
exhibit a critical current peak that is much sharper than the analogous peak of
an ordinary SQUID. Because of this, such arrays can be used as sensitive
absolute magnetic field sensors. An important finding is that, due to the
inherent asymmetry of such arrays, the device also acts as a superconducting
diode.
