Ultrafast NIR kHz and GHz Burst Laser Micro-Structuring of Polyimide Films

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

1. The manuscript demonstrates ultrafast laser inscription and ablation of polyimide using kHz and GHz pulse bursts. Can the authors more clearly articulate what is fundamentally new compared to prior works, particularly in terms of burst processing advantages?
2. Can the author explain that along with pulse burst, does linewidth variation plays a role?
3. The manuscript shows enhanced modification at 1 GHz primarily to increased laser–material coupling and plasma absorption. Can the authors clarify the relative roles of cumulative thermal effects versus nonlinear absorption under GHz burst conditions?
4. The author claimed that the fabrication of a single electrode reportedly required more than 3 hours. Can the authors discuss the scalability of this approach for practical sensor fabrication, particularly considering higher repetition rate systems?
5. The manuscript proposes applications in flexible and embedded sensors. Can the authors comment on the mechanical robustness and environmental stability of the inscribed electrodes?

Author Response

Word document of R1 reviewer and responses attached.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

See the attached pdf file.

Comments for author File: Comments.pdf

Author Response

Word document of Reviewer 2 comments and responses attched

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This study demonstrates the laser processing of polyimide films with femtosecond source. While this topic is of interest to the readers of Photonics, the manuscript in its current form is not ready for publication. My main concerns are as follows:

1. Microscopic images should be provided in Figure 4 accompanying Figure 4a and 4b for better demonstration of the ablation results.
2. How are the 3D profiles in Figure 4 obtained (maybe AFM)? More details should be provided.
3. Why doesn’t the ablation efficiency converge to 0 when Ep goes to 0 in Figure 4d? The ablated volume should in principle be 0 if no pulse energy is applied. Besides, the definition of ablation efficiency is unclear in the manuscript. What does it mean by cubic microns per µJ? How long is the ablation time evaluated in this definition?
4. What is the advantage of two-photon absorption compared to single-photon absorption? The bandgap 2.3 eV of PI is not too high so that visible light can be easily utilized to induce single-photon absorption, which should be more efficient in terms of energy absorption. The authors should elaborate more on their selection of laser wavelengths to allow only two-photon absorption.
5. Figure 3, which seems to be photos of oscilloscope screens, is not legible enough. I would recommend authors to extract the data and plot it in data analysis software.
6. Scale bars in Figure 11 don’t seem to be right. The scale bars manually added by the authors apparently have different lengths than the ones provided by the SEM system itself, especially in Figure 11c and 11d. Please clarify this discrepancy.
7. Following previous comments, several figures in this manuscript have legibility issues. For example, scale bars in Figure 13 are very hard to read, so do Figure 16a.
8. Can the authors provide an enlarged Florescence and Raman spectra for exposed PI in Figure 15? With current scale, the exposed PI shows almost an flat line, which is not very informative and clear.

Author Response

Word document with Reviewer 3 and responses attached

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript is ready for publication.