Broadband High-Precision Faraday Rotation Spectroscopy with Uniaxial Single Crystal CeF₃ Modulator

Round 1

Reviewer 1 Report

This article introduces a polarimeter based on CeF3 for broadband Faraday rotation spectroscopy. You have thoroughly analyzed the relationship between the performance of the polarimeter and several variables, and proposed methods to reduce noise and enhance optical performance. Here are some suggestions and questions regarding your article:

1.     When discussing the sensitivity of polarimeter noise to laser beam diameter, you could further explore the impact of varying laser beam diameters on the performance of the polarimeter. Is the effect consistent for different beam diameters less than 1mm? Could you provide some quantitative data to illustrate this?

2.     You mentioned achieving optimal polarimeter performance by adjusting the crystal to produce minimal intensity. Is this process easy to implement?

3.     The error in Figure 9(a) is quite significant. Could you provide a specific explanation for this?

I suggest some improvements to the quality of the English language

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The authors report a Faraday rotation spectroscopic method with a high precision in the broad wavelength region from UV to IR in their manuscript. They utilized a uniaxial single crystal of CeF2 for a modular of the Faraday rotation spectroscopy. The signals obtained lock-in amplifiers have been assessed with very careful manner by considering their experimental errors. The results were consistent with their model.

Since the presented method is important for a precise laser spectroscopy, I conclude this manuscript is worthy to publishing from Photonics if few parts in my comments are checked.

Questions and comments

1.       As for the definition of the normalized intensity in Eq. (1), it is necessary to check that the denominator does not need to be squared. And the authors should also check the same expression in Appendix-A.

2.       In Fig.5, the authors estimated the deviation angle of theta_m and gamma  as 6 and 3.2 degrees, respectively. I think both values seem to be slightly high considering the modern experimental accuracy. Are there possibilities to decrease these values by the experimental innovations?

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Throughout the manuscript, all the emphasis is put on the misalignment and crystal imperfections of the uniaxial (birefringent) CeF3 Faraday rotator. Their basic reasoning would be understandable if well-behaved laser beams were used, i.e. Gaussian non-divergent (coherent) ones. However, the fact is that laser diodes in the UV and near IR are used in combination with a lens to locus their divergent beams inside the crystal. Nothing is explained about the properties of the laser diodes, and how these affect the measurement. These concerns are reflected in the Fig.9, where the expected sinus function is not recognizable. Additionally, the by-the-way confirmation of the Verdet constant dispersion shape is not particularly original.

The authors should reconsider their arguments and focus on what is elucidated about Pb.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

I recommend the acceptance of this manuscript

Reviewer 3 Report

Thanks to the authors for their determination to address all the concerns pointed out.

Please revise references, e.g. in Fig.8 caption Equ. 13 --> Equ.11?