  The proposed numerical method, "FLAME-slab," solves electromagnetic wave
scattering problems for aperiodic slab structures by exploiting short-range
regularities in these structures. The computational procedure involves special
difference schemes with high accuracy even on coarse grids. These schemes are
based on Trefftz approximations, utilizing functions that locally satisfy the
governing differential equations, as is done in the Flexible Local
Approximation Method (FLAME). Radiation boundary conditions are implemented via
Fourier expansions in the air surrounding the slab. When applied to ensembles
of slab structures with identical short-range features, such as amorphous or
quasicrystalline lattices, the method is significantly more efficient, both in
runtime and in memory consumption, than traditional approaches. This efficiency
is due to the fact that the Trefftz functions need to be computed only once for
the whole ensemble.

Optics