The Arago–Poisson Spot: New Applications for an Old Concept

Round 1

Reviewer 1 Report

All comments are attached

Comments for author File: Comments.pdf

Author Response

Response to Referee 1

Review for manuscript “The Arago-Poisson spot: New applications for an old concept”

The authors are discussing some specific properties and applications of the Arago-Poisson spot in optics.

Particularly interesting to me is the part of the manuscript devoted to applications.

I think the manuscript is worthy of publication, subject to several comments.

We thank the referee for this.

1) page 1, line 37: “the shadow of the disk (see Figure 1c)” – Figure 1 does not have part “c”;

It was a mistake. It has been corrected (page 2, line 42).

2) page 2, line 60: “Like for Equation 8” – probably should be “Like for Equation 1”;

It has now been corrected. (page 3, line 65).

3) page 3, lines 86-96: “The size of the spot is not limited by diffraction… also beating the Rayleigh criterion”. A somewhat vague paragraph. It is necessary to clarify what the authors mean. It is known that evanescent waves can exist in the near diffraction zone that do not have a diffraction limit (https://doi.org/10.1088/0034-4885/59/5/002; https://doi.org/10.1016/j. optcom.2016.12.034), superoscillating fields

are also known (https://doi.org/10.1021/nl9002014), providing superresolution. In addition, various methods of lens apodization and special polarization states are known to reduce the focal spot (https://doi.org/10.1016/S0030- 4018(99)00729-4; https://doi.org/10.1364/JOSAA. 30.002029) including narrow annular slit to generate Bessel beams. It is advisable to add a small discussion about which of the mechanisms corresponds to the Arago-Poisson spot near and far distances from the disk.

Following the referee’s suggestion, we have added a small paragraph (lines 95-99) to discuss the different mechanisms leading to sub-wavelength resolution.

4) page 4, Figure 4 capture: “… forms a dark spot …” – however, in the text “The diffracted light interferes in a bright spot in the centre of the shadow of the disk“

This is a misprint that has been corrected in the caption of figure 3.

5) page 5, line 106: “…the first Bessel function…” – however, the zero order Bessel function in Eq. (4)

The zeroth Bessel function is supposed to be the first Bessel function. Nevertheless, to avoid any misunderstanding, we have modified the first Bessel function to zeroth order Bessel function (line 118).

6) page 5, lines 107-108: “It corresponds to the value of the square of the Bessel function for 1.75.” – should be “It corresponds to the value of the square of the Bessel function with the argument equals to 1.75.”

The referee is totally right. This has been corrected (line 120).

7) page 6, Figure 6 capture: “The solid line corresponds to the theoretical curve of Equation 1.” – written twice

It was a misprint. It has now been corrected.

8) page 6, lines 126-127: “Nevertheless, it has again to be noted that the ultimate spot size doesn’t depend on the occulting disk diameter, according to Equation 4.” – clarification of this statement is required, because of dependence on d in Equation 4.

This was indeed unclear. The argument of the Bessel function doesn’t depend on d. This has now been clarified lines (140-141).

9) page 7, line 156: “the two si …” – what is “si”?

It should have been “is”. It has been corrected (line 170).

10) page 10, Figure 9 capture: “DM: Dichroic Mirror.” – there is “BS” in Figure 9a

The figure has been corrected.

11) page 11, line 277: “…a pane wave,” – should be “…a plane wave,”

It has been corrected

12) page 12, Figure 12 caption: “self-foc: self focusing lens.” – should be “self-foc: self focusing.”

Actually, there was a problem on the figure. self-foc should only refer to a self-focusing lens. It has now been corrected.

Reviewer 2 Report

Some Figures in the work are reused from previous publications by the Authors

Compare Figs 12-13 to that in doi: 10.1209/0295-5075/ac7dfa

I suggest changing figures as per now this can be called self-plagiarism

No comments

Author Response

Reviewer 3 Report

In this paper, the authors explore a practical application of the Arago-Poisson spots in optics, focusing on the trapping of new nanoparticles in nano-size traps within the fields of astronomy, telecommunications, and precise signal delivery in a determined area. The authors provide a detailed description of the Arago-Poisson theory, examining its applicability across various fields. However, the overall presentation of the work is untidy; for example, the positioning of images needs reorganization, graphics require improvement, and there is a need for size reduction (Figure 2 occupies an entire page).

While the work is theoretically comprehensive, the novelty of the research is not clearly delineated. Additionally, the English used in this article is basic, and the style often tends to be informal. Therefore, it is recommended that the authors refine the English style to make the text more technically oriented.

The work is deemed publishable; however, the article requires reorganization to enhance its clarity by improving the English and, most importantly, explicitly stating the main objective of the research, innovative aspects, and potential future developments.

Here are my comments:

· The abstract should be more explanatory, summarizing the focus of the research in greater detail.

· The authors should review the numbering of the equations in the article (e.g., from line 60 to lines 152-156) and the references (e.g., at line 105).

· In Figures 2, 4, 5, 6, and 8, the authors must reduce the size of the axis labels.

· Delete the bullet point for sub-section 2.3.2 "Self-healing and non-diffractive properties" (line 144).

· In section 2.3.1, at line 133, the authors should better express the concept of Orbital Angular Momentum (OAM) beams (see, e.g., "Fundamentals of Orbital Angular Momentum Beams: Concepts, Antenna Analogies, and Applications," Electromagnetic Vortices: Wave Phenomena and Engineering Applications, 1-32, 2021).

· In section 3.1, the authors should justify the choice of colloids with a more detailed explanation, providing additional references.

· In section 3.1, the authors should elaborate on the basic theory of optical trapping using optical tweezers and provide a brief but comprehensive state of the art (see, e.g.,  "Nanoscale Optical Trapping by Means of Dielectric Bowtie," Photonics (Vol. 9, No. 6, p. 425), MDPI, 2022).

Author Response

Response to Referee 2

In this paper, the authors explore a practical application of the Arago-Poisson spots in optics, focusing on the trapping of new nanoparticles in nano-size traps within the fields of astronomy, telecommunications, and precise signal delivery in a determined area. The authors provide a detailed description of the Arago-Poisson theory, examining its applicability across various fields. However, the overall presentation of the work is untidy; for example, the positioning of images needs reorganization, graphics require improvement, and there is a need for size reduction (Figure 2 occupies an entire page).

This could be solved during the editing process, however in order to match the requirements of the referee, we have adapted the sizes. Besides, we have improved graphics (Fig. 2-6, 8-9, 13).

While the work is theoretically comprehensive, the novelty of the research is not clearly delineated. Additionally, the English used in this article is basic, and the style often tends to be informal. Therefore, it is recommended that the authors refine the English style to make the text more technically oriented.

We have emphasis on the novelty part of the work and improved the English throughout the text.

The work is deemed publishable; however, the article requires reorganization to enhance its clarity by improving the English and, most importantly, explicitly stating the main objective of the research, innovative aspects, and potential future developments.

We thank the referee for this comment. In order to answer her/his concerns, we have detailed in the introduction the objective of the research (lines 33-37).

Here are my comments:

• The abstract should be more explanatory, summarizing the focus of the research in greater detail.

It has been modified accordingly.

• The authors should review the numbering of the equations in the article (e.g., from line 60 to lines 152-156) and the references (e.g., at line 105).

We acknowledge there was a problem in the equation number, which has now been corrected. Concerning the reference line 105, it is about the definition of the waist of a Gaussian beam. The reference refers to A. E. Siegman who clearly states the definition of the waist.

• In Figures 2, 4, 5, 6, and 8, the authors must reduce the size of the axis labels.

The labels have been reduced following the referee’s recommendation.

• Delete the bullet point for sub-section 2.3.2 "Self-healing and non-diffractive properties" (line 144).

This has been corrected.

• In section 2.3.1, at line 133, the authors should better express the concept of Orbital Angular Momentum (OAM) beams (see, e.g., "Fundamentals of Orbital Angular Momentum Beams: Concepts, Antenna Analogies, and Applications," Electromagnetic Vortices: Wave Phenomena and Engineering Applications, 1-32, 2021).

We have already discussed the concept of OAM in the theoretical section (lines 54-57, now lines 59-62). We have now made an explicit reference to this section in section 2.3.1 (line 146). Besides, we have added the reference suggested by the referee. 

• In section 3.1, the authors should justify the choice of colloids with a more detailed explanation, providing additional references.

This is now specified, lines 257-259, together with a reference.

• In section 3.1, the authors should elaborate on the basic theory of optical trapping using optical tweezers and provide a brief but comprehensive state of the art (see, e.g.,  "Nanoscale Optical Trapping by Means of Dielectric Bowtie," Photonics (Vol. 9, No. 6, p. 425), MDPI, 2022).

This has now been done, according to the referee’s suggestion (lines 242-248). We have also added the relevant reference together with several other ones.

Round 2

Reviewer 2 Report

The paper can now be accepted

Reviewer 3 Report

The Authors have modified the manuscript according to the Reviewer suggestions.