A Surface Plasmon–Polariton in a Symmetric Dielectric Waveguide with Active Graphene Plates
Round 1
Reviewer 1 Report
Thank you for submitting your paper. The work done here draws attention to a significant subject on graphene usage. I have found the paper to be interesting. However, several issues need to be addressed properly before the paper is being considered for publication. My comments including major and minor concerns are given below:
Please consider reviewing the abstract and highlight the novelty, major findings, and conclusions. I suggest reorganizing the abstract, highlighting the novelties introduced. The abstract should contain answers to the following questions:
What problem was studied and why is it important?
What methods were used?
What conclusions can be drawn from the results? (Please provide specific results and not generic ones).
The abstract must be improved. It should be expanded. Please use numbers or % terms to clearly shows us the results in your experimental work.
Please consider reporting on studies related to your work from mdpi journals.
The authors should add a list of nomenclature for all the Greek letters and symbols used in the study.
Lines 21 and 31 there is a clear abuse of bulk citations, the authors need to remove them and properly cite each reference giving full credit, the authors need to check this issue elsewhere in the manuscript if any.
The introduction must be expanded, it is short and does not go into any details of past studies similar or closely related to this work. The authors need to enrich this section and provide critical literature review rather than generic one.
The writing style of the manuscript is inappropriate for scientific journals. Line 44 for example is not a good sentence starter, the authors must avoid using we, our, us or similar writing style and adhere to the normal article writing styles in mdpi and other publishers. The way the authors describe their materials and methods section is like a story telling on a blog.
Change section 3 to “Materials and methods” recommended.
Authors first talk about figure 1 in line 71 far away from the figure. The authors must mention any figure before (above) the figure itself not after it.
3. Fields in the structure and the dispersion relation this section can be merged with previous section.
Line 149 “damps much more slowly” what does the authors mean by that? By how much? Indicate using % or numbers to be more specific.
Explaining the graphs is not enough, the authors need to provide explanations for any interesting trends and compare them with previous literature if any.
Line 179 can the authors show the cut off region or line in the figure as well?
Line 193 so is the thickness of the barrier is the main reason for the result? Or is there other factors involved?
The title of the manuscript can be improved by indicating that there was theoretical modelling involved in the study. For example add the words “theoretical modelling” or something similar.
The results are merely described and is limited to comparing the observation from graphs and describing results. The authors are encouraged to include a more detailed results and discussion section and critically discuss the observations from this investigation with existing literature.
Conclusions can be written in bullet points for each of the subsections in the results and discussion section.
what is the percentage of self citations in the paper?
Author Response
The authors thank the referee for fair remarks. The abstract and the article were revised according to the reviewer's suggestion. Additional and explanatory information is highlighted in blue.
We used the classical approximation of plane waves in a one-dimensional eigenvalue problem to solve the Heimholtz equation inside and outside the medium, taking into account the current in the boundary conditions. The conductivity formula for graphene is based on the Kubo(-Greenwood) approximation and is taken without derivation. Numerical simulation was carried out in the Maple 18 mathematical package with an educational/academic license.
In some cases (at some frequencies), it was possible to find several solutions for one frequency, which indicates the possible bistability of the system or the presence of several independent modes of wave propagation. The calculation was performed independently by several co-authors.
1. Rewritten Abstract (problem, methods and results)
2. Improved Introduction.
3. Greek letters added to nomenclature list
4. The style of writing the work has been corrected, it is close to the rules for writing scientific papers.
5. Section 3. changed to "Results of numerical simulation of the dispersion relation".
6. The item Discussion of the results is merged with the item Conclusions.
Sincerely,
Authors
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The authors offer the effect of the energy state of the graphene layers on the dispersion properties of a planar waveguide structure 37 consisting of two graphene layers separated by a dielectric barrier layer. I just have one suggestion that a schematic illustration should be provided for visual understandings for the model used in the manuscript.
Author Response
The authors are grateful to the reviewer for comments. The suggestion was taken into account, a figure was added for a better understanding of the geometry of the problem.
Best Regards, Authors
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Dear authors,
The Abstract still need more work, please make sure to check my previous comments and update it.
Discussion and conclusions can not be in the same section!
More critical discussion is needed. The authors describe graphs but do not make any effort to scientificaslly explain their results. Authors need to explain the trends in their graphs and why they behave this way.
In many parts of the manuscript, authors uses words like "much more slowly" this is not a scientific way to express a trend. authors must use numbers or % terms to clearly express their results.
Author Response
Authors are very grateful to the reviewer for taking time to evaluate our manuscript. Many thanks for the critical comments. In the proposed version of the article, we tried to take into account and correct the shortcomings. All corrections are highlighted in green.
1. We have revised the Abstract to address your concerns and hope that it is clearer now.
2. Items "Discussion" and "Conclusions" were separated.
3. We have improved the description of Figures. Figure 4 has been modernized.
The authors agree with the reviewer's remarks, but the aim of the work is a theoretical qualitative description of the dispersion equation for antisymmetric modes. The aim is achieved, the main trends in the change of antisymmetric solutions are shown. The differences in the characteristics of the structure with doped graphene layers and inverted layers are shown. From a theoretical point of view, the character of the curves in the derivation of equations in the paragraph "Fields in the structure and the dispersion relation" is explained.
In the paragraph "Numerical simulation results of the dispersion relation" a qualitative analysis of the character of the presented solutions is given. Interesting new results have been obtained - namely, the presence of bistability.
In a theoretical study, a qualitative description and possible application of the information presented is sufficient from the authors' point of view.
At the moment, we carry on our research and concentrate on the issues of local modes of the two-layer graphene structure in more detail. These comments are very constructive and will be taken into account by the authors in future work.
We would like to thank the referee again for taking the time to review our manuscript.
Thanks a lot.
Sincerely, authors
Author Response File: Author Response.pdf
Round 3
Reviewer 1 Report
Authors need to improve the abstract further, still generic.
Author Response
Authors are very grateful to the reviewer for taking time to evaluate our manuscript. Many thanks for the critical comments. We tried to improve the abstract, We’ve made the change. All corrections are highlighted in blue. We’ve changed [The aim of the work is the theoretical study of the characteristics of plasmon mod in a structure consisting of two layers of active graphene, separated by a dielectric barrier layer. A general dispersion relation is obtained, the numerical analysis of which reveals the possibility of controlling the parameters of amplified surface modes in the region of graphene negative conductivity. In particular, their dispersion is controlled by changing the chemical potential of the graphene layers. For antisymmetric plasmons, their dependence on the barrier layer parameters was revealed. For the first time, modal bistability was also demonstrated in a limited frequency range for antisymmetric plasmons, due to the appearance of additional modes, in which the phase velocity decreases sharply near the cutoff, and the group velocities of the modes entering the bistability turn out to be opposite in sign.] to
[A theoretical study of the plasmon modes characteristics is carried out in a structure consisting of two active graphene layers separated by a dielectric barrier layer. A general dispersion relation is obtained, the numerical analysis of which reveals the possibility of controlling the parameters of amplified surface modes in the region of graphene negative conductivity. In particular, their dispersion is controlled by changing the chemical potential of the graphene layers. For antisymmetric plasmons, their dependence on the barrier layer parameters was revealed. An increase in the chemical potential makes it possible to expand the region of existence of amplified plasmons, which is accompanied not only by an increase in the amplification coefficient, but also by a shift to the region of higher frequencies of the amplified modes. For the first time, modal bistability was also demonstrated in a limited frequency range for antisymmetric plasmons, due to the appearance of additional modes, in which the phase velocity decreases sharply near the cutoff, and the group velocities of the modes entering the bistability turn out to be opposite in sign. The frequency dependences of the real and imaginary parts of the plasmon propagation constant are analyzed, the distributions of wave fields in the structure are plotted, and the frequency dependence of the depth of the plasmon-polariton is
given.], see Abstract .
Thanks a lot.
Sincerely, authors
Author Response File: Author Response.pdf
