Black Phosphorus Coated D-Shape Fiber as a Mode-Locker for Picosecond Soliton Pulse Generation
Round 1
Reviewer 1 Report
In the paper titled "Black Phosphorus Coated D-shape Fiber as a Mode-Locker for Picosecond Soliton Pulse Generation", authors demonstrate mode-locked pulse generation using black phosphorus deposited onto a side-polished fiber in an Erbium-doped fiber laser cavity. In this method, BP is coated onto the side of the fiber and interacts with the laser mode via an evanescent field to reduce the parasitic loss.
The manuscript is well-structured, and the results are effectively presented. Thus, I recommend publishing this work with some minor modifications that address the comments below:
Can the author compare the performance between the method of putting BP onto the side-polished fiber and the way of placing a thin film between two fiber ferrules?
Will the fiber become fragile after the side polishing?
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
The authors experimentally demonstrated generating picosecond pulses from an Erbium laser cavity using black phosphorous on side-polished fibre saturable absorber as a mode-locker. The pulses are chirped and have common parameter which can be obtained for different types of mode-lockers. Nevertheless, the work may be of interest to researchers working in this field. I have the following questions and comments for the authors.
1. How did the authors choose the lengths of the active and passive intracavity fibers?
2. The authors wrote that TBP~1. Why the lengths of intracavity fibers not optimized?
3. What happened in the system at a pump power >145 mW?
4. There are misprints. For example, in line 111, “27.6 ps2/km” (should be 27.6 ps2/km).
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Reviewer 3 Report
This paper demonstrates the production of picosecond pulse from an Erbium laser cavity using a new thing (black phosphorous (BP) on side-polished fibre saturable absorber (SA)) as a mode-locker. It develops an excellent evanescent field on the surface of the polished area and the stability was verified. The highest pulse energy and peak power are impressive, showing that such a new mode locker can be well used as a SA in an EDFL cavity and suitable for producing a portable mode-locked laser source. I can recommend this to be published but after some revisions.
(1) Figure 1, it is better to give a bar marking the actual size of the BP.
(2) Figure 2, legends are missed. What are the meanings for the blue dots and red curve?
(3) Figure 5, a legend is missed for the red-triangle curve.
(4) Where is the zoom-in part? it should be marked. It is also better to mark the bandwidth of the frequency peak on the figure.
(5) Some recent works on novel mode locker are missed, such as gold nanorods [Chin Opt Lett 16 (2), 020011 (2018)], fluorinated antimonene [Nanoscale, 2019, 11, 1762-1769], YbCALGO [Crystals 11 (9), 1131 (2021)] etc. for highlighting the importance of new mode-locker verification.
(6) How did the author characterize the temporal and spectral characteristics? I think it cannot be directly observed? What are the methods in details?
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
The authors did good revisions and the current version is acceptable. While, the description of chirped pulse characterization and measurement can be improved. Can the authors show the results of measured chirped phase of the pulses? If so, which will be very helpful. I think some related previous works can be helpful in these process such as PRA 96, 043851 (2017); Opt. Rev. 25, 598-607 (2018); Comm Phys 3, 151 (2020) and some other related works on ultrashort pulse characterization. If the authors have difficulty to measure the phase due to limit of devices, I suggest to discuss this into future plan.
Author Response
We did not measure the chirped phase of the pulses due to the unavailability of the equipment. However, we discuss about the chirp pulse amplification and ultrashort pulse manipulation in the revised manuscript as suggested by the reviewer.
