Generation, Topological Charge, and Orbital Angular Momentum of Off-Axis Double Vortex Beams
Round 1
Reviewer 1 Report
Reading this work is instructive. The issue is correctly described. However, I do have a few comments.
1. I think that in the "Introduction" part, one more application of optical wrirs should be added: Vortex beam as a positioning tool. Optics Express. 2022, vol. 30, no. 14, pp. 25830-25841. I think that your work can help in building tools for positioning beams carrying optical vortices.
2. In equations (1), (2) and (3) it is not clear what is the argument of the function exp. For example: E_1(x,y,z)= E_0 exp(...)(...) -> yes E_1(x,y,z)= E_0 exp((...)(...)) extra parenthesis or E_1(x,y,z)= E_0 exp(...)"x"(...) "multiplication sign"
3. There is also a paper discussing simulations of vortex propagation "Propagation dynamics of optical vortices" https://doi.org/10.1364/JOSAB.14.003054. I think this work should also be cited.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Review of manuscript photonics-2284906
This manuscript investigates the generation of off-axis double-vortex beams, and the measurement of their topological charges and mean orbital angular momenta. In contrast to on-axis vortex beams and off-axis single-vortex beams, off-axis double-vortex beams have six controllable degrees of freedom. The authors show that the mean orbital angular momentum of the off-axis double vortex beam can be easily controlled by varying the relative positions of the two phase singularities. From the simulations and experimental results, the article appears to be plausible. This manuscript can be considered for publication after the following issues have been addressed.
- It is well known that multiple phase singularity regions also exist in the intensity profile of on-axis double or multiple vortex beams. What is the difference compared to the off-axis double-vortex beam proposed in the manuscript? Please analyse this further.
- The authors claim that the average orbital angular momentum value of an off-axis double-vortex beam decreases non-linearly with increasing off-axis distance. What is the underlying reason for this "non-linear decrease"? Please explain.
- The authors show that the position of the two phase singularities of an off-axis double vortex beam affects its mean orbital angular momentum. In vortex optical communication applications that rely on orthogonality of the orbital angular momentum mode, does the position drift of the two phase singularities of the off-axis double-vortex beam have a significant impact on signal transmission? What are the advantages over on-axis double-vortex beams in communications?
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
Guo et al. create and measure vortex beams' topological charge and orbital angular momentum. Specifically, they look at off-axis double vortex beams that have not been extensively characterized. Vortex beams have applications in super-resolution imaging and particle trapping among other things and are interesting to study. The authors demonstrate that the tilted lens method and cylindrical lens methods for measuring topological charge and orbital angular momentum work as intended in this case of off-axis double vortex beams. They also show that the orbital angular momentum decreases non-linearly with off-axis distance.
The paper is well written, succint, and introduces the ideas carefully. Only one point that is missing is a description of the setup to measure the light intensity measured in figure 4.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The authors have carefully addressed my concerns and this manuscript is now available for publication.
