  The transmission across a graphene bilayer region is calculated for two
different types of connections to monolayer leads. A transfer matrix algorithm
based on a tight binding model is developed to obtain the ballistic
transmission beyond linear response. The two configurations are found to behave
similarly when no gate voltage is applied. For a finite gate voltage, both
develop a conductance gap characteristic of a biased bilayer, but only one
shows a pronounced conductance step at the gap edge. A gate voltage domain wall
applied to the bilayer region renders the conductance of the two configurations
similar. For a microstructure consisting of equally spaced domain walls, we
find a high sensitivity to the domain size. This is attributed to the presence
of topologically protected in-gap states localized at domain walls, which
hybridize as the domain size becomes of the order of their confining scale. Our
results show that transmission through a bilayer region can be manipulated by a
gate voltage in ways not previously anticipated.
