Comment on "Normalization of quasinormal modes in leaky optical cavities and plasmonic resonators"

TL;DR

This paper critically examines recent claims about the normalization of quasinormal modes in open optical systems, demonstrating that some methods are divergent and that certain radiation conditions are not satisfied, challenging prior conclusions.

Contribution

The paper provides a detailed critique of existing normalization methods for quasinormal modes, highlighting their limitations and inaccuracies.

Findings

Normalization from Opt. Lett. 2012 is divergent for finite Q modes

Silver-Mueller radiation condition is not satisfied by quasinormal modes

Previous comparison claiming equivalence of methods is incorrect

Abstract

Recently, Kristensen, Ge and Hughes have compared [Phys. Rev. A 92, 053810 (2015)] three different methods for normalization of quasinormal modes in open optical systems, and concluded that they all provide the same result. We show here that this conclusion is incorrect and illustrate that the normalization of [Opt. Lett. 37, 1649 (2012)] is divergent for any optical mode having a finite quality factor, and that the Silver-Mueller radiation condition is not fulfilled for quasinormal modes.