Interference Generation of a Reverse Energy Flow with Varying Orbital and Spin Angular Momentum Density

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript investigate the possibility of forming a inverse energy flow based on the interference light. They propose new methods for generating and shaping reverse energy flow with minimal light sources at some specific positions with different polarization. The paper is clearly written and the results are interesting. But some issues need the authors to address, which may helpful for promoting this work to broadly audience. 

 

1) The Eq.(4) and Eq.(5), i.e the equation of poynting vector and SAM density are different from the traditional definition equation. Take the Poynting vector equation as example,

 in this manuscript and  in the “Richards, B.; Wolf, E. Electromagnetic Diffraction in Optical Systems. II. Structure of the Image Field in an Aplanatic System. Proc. R. Soc. Lond. A 1959, 253, 358–379.”

So does  and  influence the final results? How about Im and ?

 

2) In the line 122, it is said that ‘the center at the point ()’. How about  in the equation(8)? Are they the same? I think in Eq.(8) can be negative if they are the same. Please indicate if they are different from one another.

 

3) It is mentioned that with sharp focusing, when () the minimum of this expression is negative. While in reality, the aperture angle usually can’t be chosen as . Does it have the reality meaning to assume  to be

Comments for author File: Comments.pdf

Author Response

Authors' answers are contained in the attached file.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

In their article, the authors touched upon the fundamental problem of controlling forward and reverse energy flow in vector structured vortex beams, provided that part of the energy is converted from forward to reverse flows. Their approach is based on the interference of radiation from a minimum number of point sources in order to obtain unbounded areas of the reverse flow. The analytical calculation uses the Richards-Wolf approach followed by computer simulation. The article is easy to read, the mathematical justification is quite clear, and a lot of illustrations are in line with the idea of the authors. I think that the article will receive high impact readers and it can without a doubt be recommended for publication, but only after the authors take into account my little comments

 

1) Two consecutive break lines (58) and (70) start with the same words "In this paper" when setting the problem. This should be corrected.

 

2) When setting the task, a new terminology ".. the asymmetric position of the two point sources.." (77), is used without previous explanations. Which two point sources in the same beam are the authors talking about? It should be clarified. It makes sense to depict this schematically in the figure

 

3) In the beginning Section 2, the authors do not explain why they chose  the Richards-Wolf formalism rather than the complex source point one, which can be easily used to achieve the same goals, but with less mathematical exercises (see, e.g., doi.org/10.1103/PhysRevA.94.023801). Moreover, the reverse energy flows in non-paraxial vortex beams have been firstly revealed and described employing exactly such an approach (see doi.org/10.1134/1.1343551). Such a comparison is worth briefly noting at the beginning of Section 2.

 

4) Among multiple illustrations of the computer simulation, I did not find even one figure with lines of both forward and reverse optical currents against the background of both longitudinal and cross-section of the beam. At the same time, such an illustration at once creates a unified view of the readers, allowing them to quickly understand the essence of the presented research. I recommend that the authors include such a plotting in the text at the very beginning, which will greatly facilitate the understanding of such a complex optical process

 

5) Generally speaking, the article occupies 25 pages of detailed theoretical studies of reverse energy flows whereas the text does mention the experiment with nothing one word. However, the readers would be still interested in hearing how the authors see direct experimental evidence of this amazing phenomenon. I think that such an elucidation will blend well with Section 5. Discussion

 

Comments on the Quality of English Language

Np

Author Response

Authors' answers are contained in the attached file.

Author Response File: Author Response.docx