On the Identification of Surface Waves in Numerical Studies
- 276 Downloads
In a recent study published in this journal, in which surface waves were investigated numerically for a certain equichiral thin film, the criterion used to determine whether or not surface waves were excited is not adequately discriminating.
KeywordsSurface-plasmon-polariton wave Dispersion relation Cavity resonance
In a recent study, the prism-coupled excitation of surface-plasmon-polariton waves (SPPWs) was investigated numerically for the interface of a metal and an equichiral thin film (ETF) . Since the constitutive properties of the ETF under investigation varied periodically in the direction of the ETF’s thickness, more than one SPPW could be excited at a given wavelength by changing the direction of the incident light. The criterion used to identify an SPPW was based on the magnitude of peaks in plots of absorptance versus angle of incidence: if the absorptance peak was greater than 0.4, then this peak was claimed to represent the excitation of an SPPW. No dispersion relation from the associated canonical boundary-value problem  was solved in order to confirm this claim.
Generally, in studies on SPPWs, many peaks may be observed in the plots of absorptance versus angle of incidence. As is comprehensively reported in the literature , some of these peaks may represent SPPWs, but this needs to be confirmed by checking that the wavenumbers agree with those that arise as roots of the dispersion relation of the associated canonical boundary-value problem. Some of the absorptance peaks may arise for other reasons such as cavity resonances. These absorptance peaks should be carefully distinguished from the absorptance peaks that can be attributed to SPPWs. The wavenumbers for cavity resonances do not arise as roots of the dispersion relation for SPPWs. Furthermore, cavity resonances are highly sensitive to the thickness of the thin film in the prism-coupled configuration, whereas SPPWs are not when the thin film’s thickness is greater than a certain threshold [3, 4].
Accordingly, some of the absorptance peaks of magnitude greater than 0.4 in Ref.  may well be attributable to cavity resonances (and/or other mechanisms) but not to SPPWs as claimed in that paper. As a representative counterexample, many absorptance peaks of magnitude greater than 0.4 were reported in Ref.  but these were not attributable to SPPWs because they did not correspond to roots of the dispersion relation of the associated canonical boundary-value problem.
- 1.Hosseininezhad SH, Babaei F (2018) Excitation of multiple surface plasmon-polaritons by a metal layer inserted in an equichiral sculptured thin film. Plasmonics https://doi.org/10.1007/s11468-018-0701-y
- 2.Polo Jr JA, Mackay TG, Lakhtakia A (2013) Electromagnetic surface waves: a modern perspective. Elsevier, WalthamGoogle Scholar
- 7.Mackay TG, Lakhtakia A (2010) Electromagnetic anisotropy and bianisotropy: a field guide. Word Scientific, SingaporeGoogle Scholar
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.