Regulating Terahertz Photoconductivity in Two-Dimensional Materials
Round 1
Reviewer 1 Report
This is an overview paper that reviewed the regulation of THz photoconductivity (PC) in 2D materials and common models describing time-resolved THz spectrum. Authors specifically reviewed regulating methods THz PC in graphene, TMDCs and TMDC/Graphene heterostructures, such as oxigen adsorption, electric gating and built-in field introduced by substrate, different gas enviroments. It is a good introduction for readers l to fast know the progress of time-resolved THz spectrum in 2D materials. The followed comments should be addressed,
1 How was Eq. (3) from ? If it was cited, the reference should be listed. Otherwise, derivation process should be shown or specified in detail.
2 What approximation was used in Eq. (2) ? It should be shown. Is the defination Delta E=E0-Eon correct ? Normally be Eon-E0. Otherwise, the negative sign should not occur
Need to proofread paper. there are some typos or wrong spellings, such as "unformed" on page 3.
note correct uses of plural, such as "the ratio between transmitted THz electric field with pump pulse at delay time of t (Eon(, 132 t)) and without pump (E0(, t))," on page 4. Should the field be fields ?
Author Response
Dear Editor and referees
Thank you very much for your effort in processing our manuscript from the editor as well as the insightful comments and constructive suggestions from referees. After reading the comments and suggestions carefully, our responses are listed as follows with a point-to-point manner, and the corresponding revisions have been highlighted with yellow color in the revised manuscript.
We hope that all these changes fulfil the requirements to make the manuscript acceptable for publication in photonics. Please do not hesitate to contact me if you have any questions regarding the manuscript or require additional materials. We look forward to hearing from you soon. T
Best Regards
Guohong Ma on behalf of all authors
Author Response File: 
Author Response.pdf
Reviewer 2 Report
1. Figures 2/3/4/12/13/14 have edge lines.
2. Format of all figures are not consistent, in terms of the font of the subtitles (a/b/c…) and the position of figure in paragraph.
3. Figure 7: The wordings inside the figure are blurry.
4. Section 4: How does the research of regulating TMD thin films PC by electrical gating looks like? The authors only discussed about regulating of graphene, then jumped into graphene/TMD heterojunction. Does the electrical regulation of TMD thin films have challenges? If yes, could the authors review the challenges?
5. Figure 7: The wordings inside the figure are blurry.
6. Section 5: For the photogating method, is it only applicable for heterojunction devices, not for graphene thin film or TMD thin film only? Could the authors discuss on this?
7. Section 6: How about graphene? Can it be regulated by photoinduced formation of elementary excitation?
8. The title of this review article refers to 2D materials, but the authors only discussed about graphene, TMD, and their heterojunction structures, and only to some extent. Are the methods the authors discussed here also applicable for other 2D materials in general? The authors may consider elaborating this to better match the claim in the title.
9. As a review article, it may be useful to list a table, summarizing all the methods the author reviewed by their functionalities and pros/cons.
English language needs to be throughly reviewed for the manuscript.
For example,
1. Line 19: briefly brief
2. Line 88: English grammar issue. Cannot understand what the authors meant.
Author Response
Dear Editor and referees
Thank you very much for your effort in processing our manuscript from the editor as well as the insightful comments and constructive suggestions from referees. After reading the comments and suggestions carefully, our responses are listed as follows with a point-to-point manner, and the corresponding revisions have been highlighted with yellow color in the revised manuscript.
We hope that all these changes fulfil the requirements to make the manuscript acceptable for publication in photonics. Please do not hesitate to contact me if you have any questions regarding the manuscript or require additional materials. We look forward to hearing from you soon.
Best Regards
Guohong Ma on behalf of all authors
Author Response File: Author Response.pdf
Reviewer 3 Report
The paper reviews the recent progress on manipulating the THZ photoconductivity of 2D materials and their heterostructures by various external means, such as gas adsorption, electrostatic gating, optical gating, and photoexcitation of elementary excitations. The paper provides a comprehensive overview of the experimental methods, theoretical models, and physical mechanisms involved in the regulation of terahertz PC in 2D materials. The paper also discusses the potential applications and future directions of this research field. It covers a wide range of topics and references relevant literature. It is a valuable contribution to the field of 2D materials and terahertz spectroscopy. However, I also have some minor concerns that need to be addressed before the paper can be accepted for publication.
(1) The paper lacks a critical analysis of the existing literature. The authors should discuss the limitations of the methods and techniques they review, as well as the future directions and applications of this research field. The authors should provide more insights and discussions on the open questions and challenges that remain to be solved.
(2) The introduction part lacks the significance of 2D layered materials for THz PC research. In this field, what are the most unique advantages of 2D materials over traditional materials in THz photoconductivity? The authors should provide more background information on the 2D materials and THz spectroscopy in the introduction section, as they should explain the motivation and significance of their review more clearly.
(3) The paper does not discuss some of the recent topics or developments in this research field that could be relevant or interesting for readers. It would be better for the authors to mention the effect of strain, twist angle, magnetic field or quantum confinement on terahertz photoconductivity in 2D materials.
(4) The paper contains some grammatical errors that need to be corrected before publication. For example, in line 19 , “a briefly introduction” should be “a brief introduction”
Overall, I think this is a well-written and comprehensive review article summarizing the current progress and future prospects for the regulation of THZ photoconductivity in 2D materials. I recommend minor revisions before publication.
Author Response
Dear Editor and referees
Thank you very much for your effort in processing our manuscript from the editor as well as the insightful comments and constructive suggestions from referees. After reading the comments and suggestions carefully, our responses are listed as follows with a point-to-point manner, and the corresponding revisions have been highlighted with yellow color in the revised manuscript.
We hope that all these changes fulfil the requirements to make the manuscript acceptable for publication in photonics. Please do not hesitate to contact me if you have any questions regarding the manuscript or require additional materials. We look forward to hearing from you soon.
Best Regards
Guohong Ma on behalf of all authors
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The authors successfully addressed most of my concerns. However, there are still several places I'd suggest the authors to modify in order to meet the standard.
1. Figure 8 is not readable. Two graphs are overlapped.
2. Figures 9/15/18 have duplicated graphs.
3. The authors should consider adding the statement/description of the challenges of regulating graphene by photo induced formation of elementary excitation to the manuscript, in order to support the author's choice of only discussing TMDs in Section 6.
Author Response
please refer to the attachment: response letter
Author Response File: 
Author Response.docx
