  Planar Josephson junctions (JJs) have emerged as a promising platform for the
realization of topological superconductivity and Majorana zero modes. To obtain
robust quasi one-dimensional (1D) topological superconducting states using
planar JJs, limiting the number of 1D Andreev bound states' subbands that can
be present, and increasing the size of the topological superconducting gap, are
two fundamental challenges. It has been suggested that both problems can be
addressed by properly designing the interfaces between the JJ's normal region
and the superconducting leads. We fabricated Josephson junctions with periodic
hole structures on the superconducting contact leads on InAs heterostructures
with epitaxial superconducting Al. By depleting the chemical potential inside
the hole region with a top gate, we observed an enhancement of the supercurrent
across the junction. Such an enhancement is reproduced in theoretical
simulations. The theoretical analysis shows that the enhancement of the JJ's
critical current is achieved when the hole depletion is such to optimize the
matching of quasiparticles' wave-function at the normal/superconductor
interface. These results show how the combination of carefully designed
patterns for the Al coverage, and external gates, can be successfully used to
tune the density and wave functions' profiles in the normal region of the JJ,
and therefore open a new avenue to tune some of the critical properties, such
as number of subbands and size of the topological gap, that must be optimized
to obtain robust quasi 1D superconducting states supporting Majorana bound
states.
