“…However, using the DtN leads to a very expensive numerical procedure in practice, as this operator is non-local. Practical algorithms are thus based on local approximations of these operators, both for the acoustic case [13,9,10,11,27] and the electromagnetic one [1,14,15,16,20,21,43,44,45]. Recently, PMLs have also been used for this same purpose [23,47,51,52].…”