Excitation of Surface Plasmon Polariton Modes with Double-Layer Gratings of Graphene
Round 1
Reviewer 1 Report
Due to the electromagnetic properties of graphene, such as lower transmission losses and sub-wavelength confinement, it is a good candidate for optical devices. To fulfill the necessary matching boundary conditions for the wave vector of surface plasmon polaritons and incident light, a grating composed of the graphene-based long-range cylindrical surface plasmon polariton waveguides is proposed. The waveguide is composed of a cylindrical silicon nanowire, silica and graphene layers.
The manuscript is dedicated to analyzing, by numerical simulation, the long-range surface plasmon-polariton waveguide in a double-layer graphene. The authors propose a grating consisting of a graphene-based cylindrical waveguide array for long-range surface plasmon polaritons. Properties of two (occurring for normal incident light) and four (for oblique incident light) couple modes are systematically analyzed as a function of the geometric parameters (periodicity of the waveguide array and the internal radius).
Equations (1) and (2), which describe the resonant wavelengths for the two modes as a function of the refractive index of the surrounding material, may be used to measure the refractive index of the medium. Higher-order modes are also investigated.
The proposed grating allows for the control of excited coupled plasmons-polaritons through the geometry, the device parameters and the interaction between the gratings. The proposed double-layer gratings of graphene have a potential application in optical devices in the mid-infrared waves. The present numerical simulation can be useful for experimentalists working in the field.
- The interaction between the two gratings is adjusted mimicked in the numerical simulation by changing the distance between them. It is necessary to discuss whether it can be also adjusted by varying materials characteristics of the system.
- The quantity \beta_0 In Fig. 1a) is neither defined nor mentioned in the text.
- It is necessary to elucidate the influence of the substrate on the results obtained in the present model.
In summary, the manuscript can be recommended for publication in Nanomaterials after a minor revision along my comments.
Author Response
Please see the attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
for comments see attached file
Comments for author File: Comments.pdf
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Reviewer 3 Report
The paper presents simulations of SPP excitation in two layers structure of graphene on nano-micro tubes and the tubes are arranged in periodic manner. There can be several plasmon modes in such structure, two because of the structure of the tube and one because of the periodic structure, as well as coupling between them is possible. Theoretically the problem is interesting however in practice it is difficult to produce. From scientific point of point it can be published however before that it needs improvements:
- I believe both TE and TM waves can excite modes in such structure, please clarify.
- Mention clearly on the graphs whether the transmission is for TE or TM polarizations?
- Are the dips in transmission due to reflection or absorption or both? need to show reflection at least for one case.
- LRSPR is usually represented by long penetration depth inside the neighboring dielectric so that the mode can propagate longer distance before getting absorbed. I couldn't find where this point is addressed. Show the penetration depth of the LRSPR.
- Apart from SPP the field enhancement can be of interest for SERS and SEF and in particular when coupling between the different modes exist where ultrahigh field enhancement occurs, see for example the review article: I. Abdulhalim, Coupling configurations between extended surface electromagnetic waves and localized surface plasmons for ultrahigh field enhancement, Nanophotonics 7(12), 1891–1916 (2018).
- LRSPR in grating configuration was reported in the two modes, spectral and angular, however the authors missed these works, see: Mohammad Abutoama and Ibrahim Abdulhalim, Angular and Intensity modes self-referenced refractive index sensor based on thin dielectric grating combined with thin metal film, IEEE J. Selected Topics in Quantum Electronics, 23, 4600309 (2017). and also: Mohammad Abutoama and Ibrahim Abdulhalim, Self-referenced Biosensor based on Thin Dielectric Grating Combined with Thin Metal Film, Optics Express 23, 28667-82 (2015).
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
for comments see attached file
Comments for author File: Comments.pdf
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Reviewer 3 Report
Following the revision I think the paper can be published now
Author Response
Thank you very much for your comments.
