  The creation of TE-mode photons in a three-dimensional perfectly conducting
cavity with one resonantly vibrating wall is studied numerically. We show that
the creation of TE-mode photons in a rectangular cavity is related to the
production of massive scalar particles on a time-dependent interval. The
equations of motion are solved numerically which allows to take into account
the intermode coupling. We compare the numerical results with analytical
predictions and discuss the effects of the intermode coupling in detail. The
numerical simulations reveal that photon creation in a three-dimensional
resonantly vibrating cavity can be maximized by arranging the size of the
cavity such that certain conditions are realized. In particular, the creation
of TE-mode photons in the lowest frequency mode $(1,1,1)$ is most efficient in
a non-cubic cavity where the size of the non-dynamical dimensions is roughly 11
times larger than the size of the dynamical dimension. We discuss this effect
and its relation to the intermode coupling in detail.
