Influence of Surface Roughness on the Resonance Frequencies and Quality Factors of Optical Cavities and Plasmonic Nanoparticles

Nanophotonic devices based on optical cavities or plasmonic nanoparticles are technologically interesting for a wide range of applications within physics and technology, and there exist by now an extensive modeling framework for designing and analyzing the performance of such resonators by use of quasinormal modes (QNMs) [1]. Real devices always come with a certain degree of surface roughness, however, which tends to change the resonance frequencies and quality factors of the resonators. Whereas full numerical calculations of individual and nominally smooth resonators can be performed with high accuracy, a full statistical analysis on a representative ensemble of resonators with surface roughness is typically prohibitively expensive. In this work, instead, we present a semi-analytical approach to investigate the statistics of resonators with rough surfaces based only on the QNM fields of the nominal smooth resonators. As an example application, we consider the case of a plasmonic nanorod, as illustrated in Fig. 1.