Femtosecond Laser-Written Small-Period Long-Period Fiber Grating for an L-Band Normal Dispersion Mode-Locked Fiber Laser

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript “Femtosecond laser-written small-period long-period fiber grating for an L-band normal dispersion mode-locked fiber laser” offers potential applications in ultrafast fiber lasers. The authors present a compelling argument for considering this as a novel device for mode-locking. However, to enhance the manuscript, I recommend addressing the following points:

 

1.     Could you include a section with a theoretical explanation or related references to support your findings? In other manner please include a short description explaining the process to improve the manuscript.

2.     Regarding Figure 1:

a)     Could you provide more periods or explain the rationale behind setting the period to 25 µm?

b)    What are the control parameters for the femtosecond laser inscription process for SP-LPFG? Specifically, could you discuss critical power for self-focusing, considering factors like wavelength, linear index of refraction, and the Kerr nonlinear index of refraction?

c)     Can you include an image (photograph) of the femtosecond laser system used in your experiments?

3.     In Section 3, Experimental Setup:

a)     Could you explain Figure 3 in greater detail or ensure all elements are included in the schematic diagram?

b)    What is the doping percentage of the fiber used?

c)     Would the experimental results differ if the refractive index of the EDFL changes?

d)    What measurement equipment (e.g., OSA, photodetector, RF spectrum analyzer) was used?

e)     Please clarify the following statement: “To facilitate easier NPR mode-locking, PCs are installed at both ends of the SP-LPFG” (lines 115-116).

4.     Regarding Figure 3: Can you include an image (photograph) of the laser system used in your experiments?

5.     Could you revise and eliminate repetitive phrases in Sections 4 (Results and Discussion) and 5 (Conclusions)?

 

 

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

In the following manuscript, the author utilized the femtosecond laser inscribed the small-period long-period fiber grating (SP- LPFG) to induce a nonlinear polarization rotation (NPR) effect for mode-locking pulses in a normal dispersion erbium-doped fiber laser (EDFL). The author should explain the following comments before the manuscript is published in the Photonics journal.

1.       What is the doping concentration of the doped fiber utilized in the experiment?

2.       How did the author optimize the length of the doped fiber to be 2.4 m and the DCF to 7 m?

3.       Why did the author utilize two polarization controllers in the cavity?

4.       Why the author did not measure the average output power of the proposed system?

5.       The intensity of the frequency harmonics is reduced. Please explain the reason.

6.       The shape of the optical spectrum looks little stage; why not observe a soliton pulse for the precise mode-locked operation?

Comments on the Quality of English Language

Minor editing of English language required

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have incorporated all the comments and I suggest manuscript to be published in current form.