Optical Design of an Integrated Paschen–Runge Spectrometer by Using a Multigrating Structure

Round 1

Reviewer 1 Report

An interesting work, which is devoted to an important task - the optical modeling of the Paschen-Runge spectrometer by using a multi-grating structure. The work gives a solid impression, well done, but there are a number of issues and comments, the correction of which will make the work clearer for the reader in my opinion. The following comments are listed in chronological order.

1. Block introduction, lines 46-52. A good review of models of Czerny Turner spectrometers with different numbers of integrated diffraction gratings is presented. But only at the end the authors write “However, the improvement and optimization of the Paschen-Runge structure by using integrated gratings are few.” What does it mean “few”. No work references provided. Please clarify this point.

2. Figure 1 – “Slit and lens”, in what reason authors indicated lens at the figure? No any words in the text below.

3. Lines 78-79. “It can be seen that the grating has a certain angle on the meridian plane, which reduces astigmatism in the wavelength range of 200-450nm.” What does this mean, how much does it reduce? Does this fact make it impossible to design a spectrometer according to this scheme in another spectral range? What will change when the spectral range is shifted? Please clarify this point.

4. Figure 2. Why is there a matrix detector in the model and not a linear one? Or, for example, a matrix detector, but rectangular. And are the elements of the detector located along a line or along an arc in the XY plane (in Figure 1 along an arc)?

5. Figure 2. Nowhere are the dimensions of the circuit and installation indicated, neither in the figure, nor in the annotation, nor in the conclusion. In general, the reader has no idea about the dimensions.

6. Lines 107-108. Why such characteristics of the detector were chosen? Do they belong to any particular matrix? Provide an example or explanation for the choice of these options.

7. Lines 114-116. What specific numerical values of the parameters were used in the simulation?

8. Table 1. Why give hundredths of the radii of curvature values of the mirror gratings? Are these strict requirements necessary for the manufacture of mirrors in the future?

9. Figure 4. A very difficult drawing to understand. The total size of the detector is about 37 mm, why exactly? Refer to your original detector parameters. What do 0.1 and 0.15 mean in the top right corner? What is the total spectral range recorded by such a detector? What results are acceptable on this detector? Why the size of the circles on the right is larger than on the left, why is it not symmetrical? Correct the caption to the figure, complete it.

10. Formula 4 is not completely clear to the reader, what are the slit and detector functions? Add refs.

11. Figure 5. Interesting results, but seem partly contradictory. Namely, why is the FVHM at 365 nm more than 2 times larger than at 305 nm, although they are symmetrical with respect to the central band at 335 nm? Also, we see a linear increase in FVHM from 305 to 275 and 260 nm, and on the other hand, FVHM 365 are approximately equal to FVHM at 395 nm, that is, we do not see such a linear growth. How do these results compare with the previous figure?

12. How will the issue of matching 7 spectral ranges on the detector be solved? Will you have gaps at the junction of the ranges of the two gratings? And is it possible to present the total (whole spectrum) dependence of the spectral resolution on the wavelength for this model?

Author Response

Thank you for your earnest comments and suggestions. All my responses are in the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

Authors have presented an Optical design of an integrated Paschen-Runge spectrometer by using a multi-grating structure in Zemax. The spectrum is divided into seven bands by grating and uses an area array detector to simultaneously receive spectral signals, which reduces the volume of the spectrometer and improves the consistency of the spectrum. Authors also provided the spectral resolution of the center wavelength corresponding to the seven different grating windows. The content of the manuscript is really interesting and manuscript is generally well. However, manuscript needs  minor revision based on the following comments:

1. Can the proposed configuration linearly split the individual spectral components in wavelength space ?

2.Did authors implement the proposed configurations in hardware ? If not, authors are advised to highlight this in the abstract. If you use Zemax for ray tracing, mention that too in the abstract and in main text.

3. Can authors mention about the abberations induced by the optical elements within the proposed configurations ?Also mention who could it affect the performance.

4. I think this modified spectrometer would be potentially useful for Optical coherence tomography Imaging, where spectrally resolved detection is mapped to CCD [1-3]. Authors could highlight this in the manuscript with the suggested references for OCT (1. https://doi.org/10.1088/0031-9155/61/21/7652 2. https://doi.org/10.1167/tvst.11.8.11 3. https://doi.org/10.1002/tbio.202000012 4. https://doi.org/10.1109/JSTQE.2016.2556226)

5.Could you mention the cost effectiveness of such configuration relative to conventional spectrometer?

6. If authors want to measure optical abberations physically, how could they do it ? Its worth to mention in the discussion or conclusions.

7. Could authors mention clearly, what are the parameters associated with the proposed configuration need to be changed for choosing the spectral band of operation as well spectral resolution?

Author Response

Thank you for your earnest comments and suggestions. All my responses are in the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors answered all questions in detail. Some of the answers are very helpful in my opinion for the readers. Therefore, it may be worth including some of them in the article, for example, response 11 (optional). And twice in response to the comments, an example of the detector "the closest detector size available on the market is 36.9×36.9mm" was given - what is the detector? Please add a Ref.

Author Response

Thank you for your earnest comments and suggestions. All my responses are in the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

Authors addressed all the raised concerns adequately and the revised manuscript could be accepted.

Author Response

Thank you for your recognition. I benefited a lot from your scientific evaluation of this article. Thank you again for your contribution to this article.

Author Response File: Author Response.docx