Particle Scattering Induced Orbital Angular Momentum Spectrum Change of Vector Bessel–Gaussian Vortex Beam

Round 1

Reviewer 1 Report

The manuscript reports the effect of particle scattering for the orbital angular momentum spectrum of vector Bessel-Gaussian vortex beam. The manuscript calculates the intensity and phase distributions of the scattering and external fields of a vector Bessel-Gaussian vortex beam in the far-field region after scattered by a particle. Then, the applicability of two main approaches to analyzing the spiral spectrum of the field is analyzed. However, the manuscript still has the following weaknesses:

1.         In Figure 4, why is the OAM modes of the incident field minus 2 equal to the scattering field?

2.         In Page 13, paragraph 2, third line, the unit of the particle radius is displayed incorrectly.

3.      In the legend of Figure 14, the “(a)-(d)” in fifth line of might be mislabeled.

4.         It is necessary to compare the results of the Mie scattering theory with the results of the electromagnetic simulation software. Therefore, please add this section.

Author Response

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Reviewer 2 Report

Some comments on this paper:

On line 131, it says "Mie scattering radar". Surely it would be a lidar? Since it uses a wavelength of 1064nm.

Along all the paper the authors remark about the importance of the size of the measurement plane. Are there some valid criteria (depending on the radius of the initial beam, to calculate the minimum necessary size for a complete unequivocal retrieval of the topological charges?

On table 1, the error is absolute, probably with the relative error the reader would be able to see better the accuracy of the algorith.

Furthermore, there is another comparison between figures 8 and 6 similar to the previous one but no quantitative difference is

On line 315 units appear to show a character which was probably was meant to denote microns.

Last, a question maybe some of the intended audience of this paper may ask is what do the authors think of the contribution of turbulence and actual propagation in the atmosphere. Would be the expected signal to noise ratio be enough to resolve these changes in the topological charge?

Author Response

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Reviewer 3 Report

The manuscript deals with the exploitation of vortex beams for applications in remote sensing engineering. In particular, the Authors investigate the effect of particle scattering in the orbital angular momentum spectrum of vector Bessel-Gaussian vortex beams, suggesting the possibility to retrieve information on the scattering particle by studying the field distribution and spiral spectrum of the vector Bessel-Gaussian vortex beam scattered by spherical particles. 

The manuscript is technically sound and could be interesting for the readership. I recommend publication with just a couple of minor suggestions.

First, in the introduction, the authors state that "OAM modes are mutually orthogonal [6] which can potentially improve the channel capacity in wireless communication systems". However, it has been proved that OAM is a particular case of MIMO system (Edfos, O. and A. J. Johansson, "Is orbital angular momentum (OAM) based radio communication an unexploited area?," IEEE Trans. Antennas Propag., Vol. 60, 1126-1131, 2012) that is useful for increasing capacity of communication systems only under particular conditions.

The authors should consider and properly acknowledge this aspect in the text. Moreover, for clarifying the usefulness of OAM systems, the authors could also suggest some other possible applications. For instance, consider referring to the following ones:

1) M. Lin, Y. Gao, P. Liu and J. Liu, "Super-resolution orbital angular momentum based radar targets detection," in Electronics Letters, vol. 52, no. 13, pp. 1168-1170, 6 23 2016.

2) M. Barbuto, M. Miri, A. Alù, F. Bilotti and A. Toscano, "A Topological Design Tool for the Synthesis of Antenna Radiation Patterns," in IEEE Transactions on Antennas and Propagation, vol. 68, no. 3, pp. 1851-1859, March 2020.

3) C. Zhang and D. Chen, "Large-Scale Orbital Angular Momentum Radar Pulse Generation With Rotational Antenna," in IEEE Antennas and Wireless Propagation Letters, vol. 16, pp. 2316-2319, 2017.

4) M. Barbuto, A. Alù, F. Bilotti and A. Toscano, "Dual-Circularly Polarized Topological Patch Antenna With Pattern Diversity," in IEEE Access, vol. 9, pp. 48769-48776, 2021.

Moreover, a discussion about the possible issues related to the divergence of standard vortex modes should be added. 

Finally, English grammar and readability could be improved.

 

Author Response

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Round 2

Reviewer 1 Report

Great thanks to the authors for their reply to my first-round question. 

As for the revised manuscript, I have some comments to the authors:

1, I notice the supplementing Fig. 1 and the revised part (Line130-135) simulate the comparison in the wavelength of 1.064cm, " -----radius a=0.5 cm. The wavelength of the incident beam is l=1.064 cm,-----". I suggest the authors give some explanations for this selection. Otherwise, the authors should unify the incident wavelength to a proper range around 1064nm.

2, The authors should check and revise their english expression carefully, and I give some examples:

a, Line 15, after being scattering

b, Line 45,  in characterized random media such

c,   Line 141, and the waist radium is

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Author Response

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