Subwavelength Hexahedral Plasmonic Scatterers: History, Symmetries, and Resonant Characteristics^†

Round  1

Reviewer 1 Report

The paper “Subwavelength Hexahedral Plasmonic Scatterers: History, Symmetries, and Resonant Characteristics” the Authors present a very systematic and comprehensive study of plasmonic resonances in a metallic nanoparticle of superquadric shape. This approach of superquadric surfaces has allowed them to consider two types of cubic particles, smooth and sharp, numerically and figure out how the sharpness affects the optical resonances. The obtained results compared with existing theoretical and numerical results. The historical inside with a detailed discussion is provided. Overall, this is an interesting and important paper, which will cause an interest of the readership. However, before I may recommend this paper for publication the following issues have to be addressed:

1.    Why Authors present the results for two different types of mesh? The refined mesh looks denser and thus more rigorous. Can you please discuss this in the text?

2.    Authors consider the lossless case only which reduces the importance of the results. Please consider a possibility to add the lossy case to the analysis. 

3.    I think that the observed resonances may be attributed to different multipoles, dipole, quadrupole etc. Please consider this possible addition and discuss in the text.

4.    The text and grammar need careful reading because there are many typos and mistakes here and there in the text (“solution is the a cube”, “an infinite right circular cylinder” etc.). 

Author Response

Please read the included pdf file!

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript by D. Tzarouchis et al. presents a very good investigation on the resonant characteristics of hexahedrical inclusions. In particular, the inclusions whose external surfaces are described by the so-called "superquadratic" surfaces are investigated. As highligthed in the title of the manuscript and abstract, the Authors focus their attention on three main aspects: history, symmetries and resonant characteristics. Therefore, this Reviewer has checked carefully that the Authors have satisfied these points through the manuscript in order to provide tot he readership a solid content from both scientific and historically point of view.

In general, the manuscript is well-written and timely. The method and scientific approach is good and suitable for reaching the aim of the manuscript. In order of appearance, the Authors introduce  the superquadratic surfaces and superspherical solids in Sec. II, and the corresponding equations for evaluating the Cross sectional Area and Volume (eq. 2 and 3, respectively). Then, they present the resonant characteristics of a smooth and sharp cube in Sec. III. Sec. IV is devoted to an historical comparison of the resonance position in terms of negative epsilon for the same cube. Finally, in Sec. V and VI the Authors propose a scheme for categorizing the surface potential exerted at the plasmonic range. According to my opinion, this section may turn out to be interesting for the readership.

To conclude, the manuscript requires a minor review by the Authors. Among the three main aspects presented in the paper, this Reviewer finds out that the hystorical part misses of some papers that represents important milestones in the use of the terms "superquadratic" or "superspherical". Therefore, this Reviewer have checked the cited references by the Authors and other the references of related recent works in order to have a clear overview of the current status on the research topic. 

Some examples to be considered for improving this aspect are:

1) S. Onaka, “Superspheres: Intermediate shapes between spheres and polyhedra,” published in 

Symmetry, in 2012.

2) T. Miyazawa et al. “Supersherical-shape approximation to describe the morphology of small crystalline particles having near-polyedral shapes with round edges,” Published in Journal of Mathematical Chemistry in  2012.

3) Ramaccia et al. "Super-spherical core-shell nanoparticles: Nanostructured materials enabling applications in the visible regime" published in Metamaterials proceedings in 2016

4) C. Noguez, "Surface Plasmons on Metal Nanoparticles: The Influence of Shape and Physical Environment".published in Journal of Physical Chemistry C in 2007.

5) B Sturman et al. "Metal Nanoparticles with Sharp Corners: Universal Properties of Plasmon Resonances" published in Europghysiscs letters in 2013.

Author Response

Please read the enclosed file

Author Response File: Author Response.pdf