Advances in Ultrafast Fiber Lasers for Multiphoton Microscopy in Neuroscience

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In this manuscript, the authors explored the potential of ultrafast fiber laser sources in neuroscience, highlighting their appeal due to superior heat dissipation, high gain, durability, compactness, cost-effectiveness, portability, and ease of use. I think the work discuss a current topic and highly relevant to the imaging community. However, I have some major concerns.

 

The presentation and language are my primary criticisms. The work requires careful revision and reorganization to ensure clear communication.

For instance: the title of section 3.2 says "two photons label-free imaging". This makes me question whether the authors have proofread their manuscripts thoroughly.

When it comes to the demonstration of results and discussion, Fig3 and Fig11 are well-organized to convey the message, whereas the majority of other figures do not. The panels in other figures each present separate, somewhat unrelated information. This is a continuation of the critique of the writing, in which the subject matter is discussed but not connected to the readers. 

I would recommend that authors use tables to present their literature review and figures to provide a clear comparison of methods when differences are discernible. 

A few of these issues (not an exhaustive list) that a competent proofreading service can address are as follows:

- The abstract is superfluous upon initial reading, and the passage can be shortened.

- L30: rephrase "sweet" in "laser wavelengths must be constrained to sweet areas such as 1300 and 1700 nm"

- L31: it is misleading to concentrate on rep-rate and pulse width as the most significant difference (instead of pulse power); a 3P theory work is more appropriate than specific examples of 3P here.

- What is meant by "democratizing these imaging techniques (using commercial lasers)" in Section L36?

- Provide a citation for "adapting various types of gain fibers" in L45.

- L52: The enumeration of osc and amp development>material-based and optical-phenomena-based is redundant and vague.

- What do authors mean by quoted watt level in sentence L57? please provide quantitative values for pulse power

- L71: I recommend eliminating "The paper is concluded in section 5"

- L74: 10nJ-100fs-1000nm author list must be supported by theory or applied example of power limitations. I've built 3P systems at 8nJ-180fs-800nm.

- Fig1: None of the acronyms are expanded in Figure 1. The figure requires explanation. I do not understand what the authors are attempting to demonstrate with respect to the principles of fiber lasers, as each panel depicts a distinct trajectory and contains no common elements.

 

Comments on the Quality of English Language

please refer comments above.

Author Response

please see our responses in the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Review of manuscript “Advances in Ultrafast Fiber Lasers for Multiphoton Microscopy

in Neuroscience”

Journal: “Photonics”

Manuscript ID: 2625624

Overview:

The review at hand delves into the contemporary trends and the potential of fiber lasers, particularly their expanding role in neuroscience for both structural and functional brain imaging. It commences with a primer on multiphoton microscopy (MPM) and the incorporation of commercial lasers therein, subsequently spotlighting the ascendancy of fiber lasers, from their compact design, autonomy from alignment, and other distinct laser attributes. The authors make a claim that imminent innovations in fiber laser technology will encompass a vast spectrum of applications within neuroscience. In Section 2, the authors elucidate the principles of ultrafast lasers, offering a recap of the latest progress in its components. Section 3 pivots to a synthesis of Fiber Laser-based Multiphoton Microscopy (FL-MPM) applications pertinent to neuroscience. Meanwhile, Section 4 articulates the anticipated strides in fiber laser technology and the potential for its comprehensive assimilation within the neuroscience community.

Conclusion:

The authors have commendably gathered contemporary research and advancements in the application of fiber lasers in neuroscience. Nonetheless, the manuscript requires further refinement to ensure clarity and connectivity across topics, especially for interdisciplinary readers unfamiliar with the field. Presently, the narrative seems more like a collection of facts rather than a seamlessly integrated message. To elevate the manuscript to the desired standard, it is essential that the significant concerns outlined below be addressed before considering it for publication.

Major Concerns:

While the review offers notable insights to current advancements in the field, some potential areas for concern are identified which requires further clarification:

 

1.       Given that the primary objective of review articles is to cater to a broad audience, ranging from novices to seasoned experts, the manuscript necessitates significant refinement. The current rendition omits critical foundational explanations and context that would be pivotal for readers unfamiliar with the subject matter. Providing succinct descriptions of the essential concepts enumerated below would profoundly amplify the manuscript's appeal and accessibility to a broader readership:

                                                  i.      In introduction authors should describe “What is Multiphoton Microscopy (MPM)”

                                                 ii.      Incorporating a schematic illustrating multiphoton microscopy would be beneficial.

                                               iii.      A discussion on Two/Three/THG microscopy is conspicuously absent in section 3.

                                               iv.      Line 112-113, authors writes “In order to meet higher pulse energy requirements, the similariton and all normal dispersion regimes were discovered.” But does not describe what are Similaritons nor provide a citation, this statement require further elaboration and referencing regarding "Similaritons."

                                                 v.      In line 101-103, Author writes “The important elements in the laser cavity are gain fiber for amplifying the pump power, an isolator to ensure unidirectional light propagation inside the cavity and a saturable absorber to achieve the modelocking of propagating modes.”. While it's accurate that saturable absorbers aid in achieving mode locking, their fundamental role lies in selectively transmitting high-intensity light portions and absorbing the lower intensities. This process facilitates the amplification of the desired mode within the gain cavity. For readers who may not be experts in this domain, an elementary explanation covering components like mode locking, saturable absorbers, and the gain medium would be exceptionally valuable.

 

2.       The manuscript would benefit from a more comprehensive juxtaposition of the discussed concepts and the prevailing discussions in the broader literature. This comparative analysis seems conspicuously absent in the current draft. To provide further clarity, consider addressing the following specific instances:

                                                   i.      Beyond MPM, which imaging techniques are considered its competitors?

                                                 ii.      What advantages does MPM possess over these alternatives, and how has this superiority contributed to its extensive adoption in neuroscience?

                                               iii.      For the varied microscopy techniques mentioned, which specific regimes are most apt, and where do potential opportunities lie for fiber lasers to bridge existing gaps?

3.       Lines 121-123 indicate, “Saturable absorbers have recently been developed using 2D materials such as graphene, transition metal dichalcogenides (TMD) [19], topological insulators (TIs), black phosphorus (BP), and MXenes [18].” However, the author does not delve into the significance of these developments in the context of saturable absorbers. An exploration into the merits, drawbacks, and both the distinctions and similarities among these novel materials is absent. Such gaps can leave readers perplexed and project an impression that the paragraph lacks cohesiveness with the manuscript's broader theme.

4.       On lines 123-124, the author mentions, “Among these, Graphene SA is currently utilized in ultrafast fiber laser development and has been integrated with two-photon microscopy for neuroscience applications.” However, the text omits an explanation as to why Graphene SA holds an edge over other saturable absorbers specifically for neuroscience applications. In the absence of this broader contextual link, the manuscript seemingly presents a mere aggregation of factual achievements from the domain without offering deeper insights into how these advancements correlate with the overarching narrative of fiber lasers in neuroscience.

5.       In lines 129-130, the authors assert, “The predominant share of optogenetics and imaging research in neuroscience is heavily dependent on femtosecond pulses with repetition rates spanning from a few kHz to a few GHz.” Yet, they don't elucidate the reasons for this dependency nor furnish empirical data to substantiate their statement. In the absence of a concise rationale, this stance risks being perceived as a mere personal viewpoint of the authors, lacking transparency for the readership. It would be prudent for the authors to furnish a concise rationale supporting their claim, accompanied by pertinent references.

6.       In lines 140-141, the author introduces terms like “Soliton Self Frequency Shift (SSFS), supercontinuum generation, and multi-wavelength generation,” yet fails to elucidate or provide references for a lay reader to grasp concepts such as SSFS and Supercontinuum generation.

7.       At lines 226-227, the author observes that “the pump spectrum unmistakably peaks at 975 nm and the intensity of the ASE spectrum is notably subdued,” however, the manuscript doesn't elucidate what the ASE spectrum entails.

8.       Pertaining to the techniques delineated in section 3.3:

While the author has cataloged the experimental conditions from recent studies, there seems to be a lack of a comprehensive perspective addressing certain critical aspects:

                                                   i.      The prevalent obstacles encountered in two-photon/three-photon/THG microscopy remain undiscussed.

                                                 ii.      Within the broader framework of aligning appropriate lasers for each microscopy variant, the manuscript does not detail the standard parameters, such as pulse width, repetition rate, and power, that are typically required.

                                               iii.      Regarding the employment of multiphoton microscopy in neuroscience, the manuscript could benefit from shedding light on the ongoing discourses and prevailing trends in the discipline.

9.       Within Sections 4.1 and 4.2, the authors outline a series of anticipated advancements in SA and Laser technology. However, they fall short of providing context regarding the potential capabilities these advancements could introduce, especially in addressing existing gaps in neuroscience imaging.

Minor Concerns:

1.       In abstract at line 8-9, Author writes “Furthermore, we demonstrate the fluorescence and label-free two- and three-photon microscopy applications in neuroscience using femtosecond fiber lasers.”, the term "demonstrate" is misleading since the authors are reviewing existing literature. A more suitable term like "document" or "describe" would be apt.

Author Response

please see our responses in the attachment

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

 

 

In this manuscript, Srinivasan and Yildirim provide a comprehensive and in-depth review of the latest advancement in ultrafast fiber lasers for multiphoton microscopy application in neuroscience. Both fundamental laser design principles and the most recent neuroscience applications are covered, and the author also ends the paper with insightful future direction and outlook of this field, which makes this review highly beneficial for both laser engineering and the neuroscience community. However, there are still a few minor concerns that draw attention and could be further improved:

1. The author effectively highlights the advantages of fiber lasers in multiphoton microscopy applications. However, it would enhance the manuscript's comprehensiveness to also address the disadvantages in comparison to traditional laser systems. A detailed comparison or a table illustrating the pros and cons of both laser types would provide valuable insights and aid readers in better understanding laser characteristics in subsequent sections.

2. L20-21, other advantages of MPM, like longer wavelength for deeper penetration depth, could also be mentioned here in addition to “high resolution imaging capability”.

3. L30-31, a few more words about the 3P laser constraints could also be useful here, e.g. water absorption, thermal damage, etc.

4. L47 and L47, it is better to use the consistent unit for the laser wavelength in the whole paper.

5. Figure 1, it is worth mentioning the full name of WDM in either the main text or the figure legend.

6. L215, is this specific fiber laser configuration used in the MPM? Could be useful to mention here and link with the following sections.

7. In 3.1, temporal focusing microscopy could also be mentioned here as a popular application of fiber laser.

8. L262, “Because of” is inappropriate here.

 

 

Author Response

please see our responses in the attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have addressed all my concerns, and I have no further questions. I appreciate the authors' effort in revising the manuscript, which has significantly contributed to the overall quality and significance of the work.

Reviewer 2 Report

Comments and Suggestions for Authors

The Authors have sufficiently addressed all the concerns raised in previous review. A minor edit of providing citations in section 2 for introduction of types of microscopy techniques would be beneficial.