Sensitivity approach for eigenmode characterization of structures with open boundary conditions

The computational models of open resonant nanophotonic structures include perfectly matched layers in order to realize a proper transition to free-space for the electromagnetic waves. As a consequence, the eigenvalue spectrum is spoilt by unwanted eigenmodes which are trapped within these layers. In the context of the finite integration technique we apply a computational inexpensive sensitivity analysis in order to identify those undesired eigenmodes.