Broadband Mid-Infrared Frequency Comb in Integrated Chalcogenide Microresonator
Round 1
Reviewer 1 Report
The authors numerically studied mid-IR optical frequency comb generation in a chalcogenide microresonator. First of all, the article does not correspond to the scope of the journal /Sensors/. The scientific level of the article also does not correspond to the level of the journal.
The authors suggest using a laser pump source 9 μm with a power of 550 mW, which does not look very plausible. What narrowband sources have such parameters? The authors considered critical coupling, in which almost all pump power should launched into the resonator at exact resonance. Will the resonator be damaged at such powers? My concern is whether the self-focusing power will be exceeded in this case? Moreover, a part of the pump power is thermalized, and the temperature rises. Can it rise above Tg? These questions are not discussed in the article and estimates are not given.
All demonstrated regimes of pump conversion and comb formation are well known.
As far as I understand, the authors do not take into account the frequency dependence of Aeff (Aeff = 40.2 um^2). With a large spectrum width, this dependence can strongly affect the simulation results.
Many glass parameters are not known to the authors, so they take some estimates (not very clear, true or not). The intrinsic Q-factor was set to be 2x10^6 which seems too high for real devices. For example, Q-factor of a ChG microresonator measured at 4.5 um was only 1.1x10^4 [https://doi.org/10.1364/PRJ.386395].
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
MIR comb is an interesting topic. The authors designed a sandwich integrated ChG microresonantor with a wide transmission and high nonlinearity. The research work was organized well and the results sound reasonable. But, I have the following questions.
The authors considered a sandwich waveguide structure, which featured thichness-insensitive dispersion. How to understand the property of thickness-insensitive dispersion in the waveguide? Why is the thickness insensitive to the dispersion?
On the section of generation of MIR microcomb, the authors calculated the third-order nonlinearity. What method was used to creat or enhance the Kerr nonlinearity which could compete with the linear dispersion?
How to creat or enhance the high-order nonlinearity? Which order of nonlinearity was considered here?
On Page 6, it is necessary to explain the Kerr gain coefficinet g, where the new parameter V_eff appear.
The authors designed a geometry profile with two zero dispersion wavelength to obtain a broadband comb. Did the zero dispersion lead to the near-to-zero group velocity dispersion in microresonantors?
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
The manuscript presented a fancy MIR Kerr comb based on an integrated ChG platform. Simulation results indicate a promising bandwidth of 5.1 μm. The authors proposed a feasible fabrication scheme, making the proposed device practical. The simulation results substantiate the conclusions, and the work is appropriately contextualized. The presentation quality is generally high, with a well-written paper and clearly formatted figures. Consequently, I recommend acceptance of this manuscript with minor revisions.
To further improve the manuscript, I would like the authors to address the following questions and suggestions:
- Have the authors taken into account the absorption loss from the ChG material in the simulation? If so, please clarify the value used.
- Can the authors simulate and discuss the impact of temperature on the device's performance?
- How about the predicted stability of the ChG waveguide under relatively high optical power?
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The revised article and responses to the comments seem to be satisfactory. Therefore, I recommend the article for publication in Photonics.
