Research Progress on Narrow-Linewidth Broadband Tunable External Cavity Diode Lasers

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This review paper, “Research Progress of Narrow-linewidth Broadband Tunable External Cavity Diode Lasers,” systematically surveys NBTECDLs. The authors classify NBTECDLs by external cavity type, trace their development history, analyze the performance of various designs, and summarize the current state of the technology. The paper also discusses key challenges and potential future directions, providing a concise overview of progress and trends in NBTECDL research.

The manuscript is generally well-organized and clearly written. The paper can serve as a resource for scholars in the field of semiconductor lasers, helping them familiarize themselves with recent advances in external cavity diode lasers. The references are appropriate for a review study, and the authors have included a substantial number of recent studies. Please find below my comments:

• In figure 1 the collimator element is missing, even though its label "L" is present.

 

• In lines 82-83 the authors state: "The results show that the power is inversely proportional to the linewidth. The formula is as follows:" The fact that power is inversely proportional to the linewidth can not be immediately concluded from equation 3. I suggest authors add more discussion and elaboration. 

 

• In each subsection of Section 4, the authors report recent progress for a specific class of NBTECDLs, concluding with a summary table. These tables are very helpful. However, it would further improve readability if each subsection ended with a short narrative paragraph that synthesizes the listed studies—highlighting their key advantages, disadvantages, and overall trends. This would help readers quickly grasp the state of the art without relying solely on tables.

 

• I suggest the authors proofread the paper, as there are typos present all over the paper. 

  Few examples include:

  • Line 57: “Figu re 1” should be “Figure 1.”

  • Line 86: “chargeof” should be “charge of.”

  • Line 453: "At A current" should be "At a current"
• In review papers like this paper in which many abbreviations are introduced, it can be beneficial for the readers if authors add a table to the paper with all the abbreviations. 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Chen et al. focused on a review paper about the progress of Narrow-linewidth Broadband Tunable External Cavity Diode, which is an interesting and important topic. I appreciate their effort to review developments in this field, as such a paper could be valuable for researchers. However, the current manuscript has several issues related to writing quality, organization, and presentation. The paper lacks sufficient depth in summarizing previous research, and crucial explanations, comparisons, and analyses are notably absent. A good review paper should provide a comprehensive summary of past research, include as many relevant references as possible, critically analyze progress, highlight challenges, and explain how different studies relate to each other over time. With the current version, I cannot recommend the manuscript for publication. However, I believe this is a key research field and many researchers are working. Therefore, I would like to give the authors another opportunity to improve it significantly by rewriting and reorganizing the manuscript based on my comments below.

 

1. The introduction is not sufficient. First of all, there are no citations included. How can you present all the scientific information in the introduction without referencing sources? I also expect the introduction to include the following items in a more scientific manner.

• Background & Context: Introduce the topic and key concepts.
• Importance: Explain why the topic is significant in applications.

• Current Research: Summarize major developments so far.
• Gaps & Challenges: Highlight unresolved issues or limitations.
• Purpose & Scope: State the aim of the review and what it covers.
• Outline (optional): Briefly mention the paper’s structure.

Therefore, I recommend rewriting the introduction.

2. Figure 1 uses the symbols r1, r2, r3, d, and L. Please explain these symbols in the figure caption.
3. On page 2, there are three references provided. However, in the section “The structural types of NBTECDLs” on pages 3, 4, and 5, I did not see any references. How did the authors obtain this information? There are also several equations and structures used. Even if the equations are well-known and simple, proper references are still required.
4. In the Research progress of NBTECDL, the authors presented previous works on different structures in chronological order, which is good. However, I find there is a lack of detailed information about each study. The authors only summarized the work in each publication, but I suggest they also explain the limitations or missing parts of each study. Specifically, they should describe how the improvements were made in each structure over time.
5. Please rearrange the figures for better consistency. For example, the font size in some figures is smaller than the text (e.g., Figures 2 and 3), while in others, like Figure 6, it is larger. Make the font size uniform across all figures. Also, in Figure 3, there is a line before the figure caption, which should be removed.
6. The formatting of Table 3 needs to be revised.
7. In line 57, the word “Figure” should not have a space inside; please correct it.
8. In line 87, the authors mentioned “the above equation.” Please specify which equation by including the equation number.

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Please check English, especially sentence structure, so that everyone can understand it clearly.