Analysis of the Passive Stabilization Methods of Optical Frequency Comb in Ultrashort-Pulse Erbium-Doped Fiber Lasers

Round 1

Reviewer 1 Report

In this review, the current state of the art in stabilizing the output radiation of ultrashort-pulse fiber lasers are described and the methods to reduce the magnitude of fluctuations in the amplitude-frequency noise of output radiation are analyzed. Hence, we recommend this manuscript to be published. But there are some questions need to be corrected and explained.

1. Can the authors give some comparison comments on solid state laser and fiber laser.

2. In fiber laser, the total GVD value of the laser cavity affects the generation soliton type. Can you give the specific value?

3. Many 2D materials-based saturable absorbers were demonstrated to be the good candidates for generating conventional solitons or dissipative solitons. Can the authors give some comments.

4. The authors discuss about ultrafast fiber laser. I suggest the authors see the paper "Ultrafast Science to Capture Ultrafast Motions", Ultrafast Science, vol. 2021, Article ID 9765859, 2 pages, 2021. (https://doi.org/10.34133/2021/9765859). Please add more discussion on ultrafast fiber laser in introduction part.

Author Response

Thank you very much for your interest in our article! We have made changes in accordance with your comments.

1. A paragraph has been added in the introduction, which describes the main comparative characteristics of fiber and solid laser cavities.
2. At the beginning of the "Soliton generation mode" section, the value of the total dispersion of the resonator has been added, in which there is a soliton generation mode.
3. Added a comment about your comment in section 4. «As shown above, the generation mode of USP fiber laser mainly depends on the total cavi-ty dispersion. Various materials used as saturable absorbers have almost no significant ef-fect on the generation mode. A small effect of a saturable absorbers on the generation mode is possible provided that it has a narrow spectral bandwidth of operation and be-haves like a spectral filter.»
4. Thank you very much for the information about this magazine. We've added a link to it.

Author Response File: Author Response.docx

Reviewer 2 Report

This proposed paper entitled "Analysis passive stabilization methods of optical frequency comb in ultrashort pulse Erbium-doped fiber lasers “The manuscript can accepted since it is scientifically sound provided a few corrections have been made. 

1)   In the abstract section, “Coming up with main noise characterization in mode-locked fiber lasers, we further consider the influence on laser operation of primary generation regiumes starting up in cavities, such as solitons, stretched pulses, similaritons, and dissipative solitons.”

What is regiumes, please correct it wrong spelling given.

2)   In page 13, “When propagating in a fiber with a negative GVD value,

a non-soliton ultrashort pulse tends to a soliton form of the nearest order, as described in more detail above, as a result of which energy is transferred to dispersive waves, which negatively affect the stability of radiation and the maximum peak power.”

Please check the sentence, since it could give a wrong indication to the statement written here.

3)   Also, in page 13, “When operating in the stretched pulse generation mode, in equation 6, to find the jitter, the values of the parameters Iω и It will be equal Iω = 0,2647EΔΩp2и It =0,2647EΔtmax2, where ∆tmax is the maximum width of the pulse duration by half-height.Taking the chirp as the maximum value, and substituting the values of Iω и It in Equation 3, then for T ≫ τg the equation will have the form:J2 = 0.362hνE2(g − 1) [C4D22Ωg……….” Please correct the symbol written accordingly.

Author Response

The team of authors would like to thank the referee for a careful reading of the article. As recommended, we have made the following changes:

1) We fixed a typo in the word regiumes

2) We have removed this sentence from the article in order to simplify the understanding of the topic being described and eliminate the occurrence of possible misconceptions

3) We have made an adjustment to the description of formula 19 (now 25)

Author Response File: Author Response.pdf

Reviewer 3 Report

The manuscript by Stanislav et al. presents a review of the current state of affairs in the field of stabilization of ultrashort pulse (USP) fiber lasers. The topic is interesting, and the ultrashort pulse fiber laser community will find the paper useful. However, to achieve that, the review paper needs to address this interesting topic appropriately which is missing in the current version of the manuscript authors submitted.

Several comments/suggestions regarding the explanation/presentation which are required to be solved/corrected and explained as per comments and suggestions before publication (Major revision):

(1)   In the title of the paper, the authors wrote “Analysis passive stabilization methods of optical frequency comb in ultrashort pulse Erbium-doped fiber lasers” which includes the term “frequency comb”, but the authors did not introduce the frequency comb (as noise in fiber laser?) in the paper. To follow the title (topic) of the paper, the authors must introduce the frequency comb in the introduction and explain in detail how the frequency comb is referred to as a noise in the fiber laser with related references. The authors also need to explain the ultrashort pulse formation mechanism in fiber laser cavity in a way so that noise/fluctuation formation in laser pulse also can be understood.

(2)   The introduction is very short and not well organized to describe the contents of this review paper. The introduction should give information regarding the origin of noises/fluctuations in the fiber laser (soliton) and systematically explain the history of stabilization methods reported so far. Please write the introduction part in more detail along with introducing and explaining all the keywords of this review paper.

(3)   Authors presented several fiber laser cavities (ring) for ultrashort pulse laser and explain the operating principles and the effective cavity parameters for noise/fluctuations. In most of the cases, there are no related experimental results showing the laser pulse quality characteristics from those laser cavities and other results to properly address and compare the noise/fluctuations in the fiber laser pulse. Please provide the related experimental results from the appropriate references along with the proposed laser schemes/cavities and compare the noise/fluctuations from various fiber laser cases (as proposed as schemes).

(4)   Most of the figure legends are too short (difficult) to extract the main point/information from the figures. Please provide a brief explanation of each in the figure legend.

(5)   If the figure is not original and copied/generated from other report/articles, please provide the origin/reference number for that figure (such as Figure 4, 5, 6, 8, 9, 10, 11, 12, 13, 15, 16, 17, 18, 19, 20, 21. 22, 23, 24). If not original figures, authors should have permission to reuse the figures by journal copyright policy.

(6)   Authors presented several equations in the manuscript for discussion, but equation numbers are not following the numerical order. After Eq 24 there should be eq 25, not eq 26. After Eq 26 there are also typo for equation 27 and 28. Please write the Equations not to make any mistakes with the order number.

(7)   In eq 1, the denomination term is ⟨P(t)²⟩_T’, but it is introduced in the next line as ⟨P(t)²⟩_T – average optical power. Please make the correction.

(8)   It is demanded in an ideal review paper to provide the perspective/future works/prospects of the topics which the authors described in the review paper. It will be a better presentation if the authors add another section named Perspective and Future Prospects (or a related similar section) before the conclusion and explain the current standpoint of noise stabilization in fiber lasers and possibilities of improvement in the noise stabilization in fiber laser employing the discussed techniques or any new technique.

 

(9)   There are typos in the paper: such as “Abstruct:, regiumes (in Abstract)”. Please make sure there are no typos in the manuscript.

Author Response

Thank you so much for such a large and high-quality review on the merits!

We have prepared the answers:

1. The following section 2.3 has been added
2. Introduction has been expanded and revised as recommended by the reviewer
3. Proceeding from that the noise characteristics of mode-locked fiber lasers are impacted by the general characteristics and parameters of the laser, such as net cavity dispersion, cavity loss, the thermal stability of the laser, and quality of the pumping laser, we have discussed the influence of these and other factors on the noise properties in this review. Regardless, we believe that these characteristics are not coupled to the type of resonator (cavity), in other words, the parameters affecting the noise are variable independently of the type of cavity. (For example, a fiber mode-locked laser with near-zero dispersion can be assembled with an NPE or NALM cavity, or any other type of cavity discussed in the review). To the best of our knowledge, there are no experimental investigations to study the noise properties of lasers with the same basic parameters and characteristics but with different cavities. Moreover, the effect of cavity loss on noise, which is related to the number and type of elements attending in the laser cavity, should be taken into account, generally, the increase in cavity loss increases the noise (RIN and jitter) in the laser due to the increase in the ASE. A higher cavity loss assists in suppressing the coupling from a random shift of central frequency to the timing jitter. Nevertheless, in this chapter, we considered it necessary to present fiber laser construction schemes as possible examples of internal loss optimization.
4. Some figure captions have been added or changed
5. All figures used in the article were made by the authors of the article. Of course, they were created based on data and ideas obtained from various works, but these data and main ideas were reworked, modified and adjusted by the authors. Links to all works, data and ideas from which were used in the figures are in the text or figure captions.
6. Ordinal numbers of equation have been corrected
7. ⟨P(t)2⟩T' This is how the comma sign at the end of the formula was displayed. The comma has been removed
8. The final section has been modified and supplemented.
9. All typos we found have been corrected.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Authors updated the paper and given answers following the comments/suggestions given previously. 

Still there are several corrections required.

In the introduction, authors used the abbreviation 'UCI' but did not introduce the term when it was first appeared in the manuscript.  What is "UCI fiber" mentioned in the introduction. 

Please provide full form of all acronyms/abbreviations when they first appear in the manuscript. 

Author Response

Thank you very much for the shortcomings!

UCI has been corrected to USP. Other abbreviations were also checked for consistency.