On the regime of validity of volumetric and boundary perturbation -based scattering models for rough multilayer

This paper is primarily aimed at formally resolving the seeming discrepancy between the corresponding regimes of validity of two different kinds of perturbative formulations based on boundary perturbation (BPT) and volumetric perturbation (VPRT), respectively. Instead of resorting to purely intuitional considerations, the VPRT regime of validity is obtained by using a formal derivation, which also permits to understand in detail the meaning of the involved approximation. As a result, we demonstrate that these two theoretical constructs addressed to rough multilayer scattering can be now regarded in a conceptually coherent frame. Theoretical analysis is also supported by numerical results.