Controlled Growth of Multifilament Structures with Deep Subwavelength Features in SiC via Ultrafast Laser Processing

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

1. The authors state on line 112 of the main text that the elliptical beam plays a role in regularising the positions of "multifilaments." However, the ellipticity used in this study (1.27) is relatively low compared to values cited in the referenced literature. It is recommended to further increase the ellipticity of the laser beam and systematically investigate the changes in multifilament distribution patterns under conditions of higher ellipticity. This would strengthen the reliability and persuasiveness of this conclusion.
2. The authors state on line 128 that the focused spot diameter is approximately 1.1 μm, but this value seems inconsistent with theoretical expectations. Based on standard optical theory, the diffraction-limited spot size for a 1030 nm wavelength laser focused by a 0.5 NA objective lens should be approximately 2.5 μm. Please could the authors provide clarification on the measurement method used to determine the experimental spot size, or supply the relevant calculation basis for this value?
3. The authors cite existing research on line 133 of the main text, noting that multifilament structures parallel to the polarisation direction can form inside SiC. However, the underlying formation mechanism is not explored in depth. For instance, why do the filaments tend to align parallel to the polarisation direction, and would this structure rotate if the laser polarisation direction changed? This phenomenon might share similarities with the formation mechanisms of nanogratings. It is recommended to further discuss the physical origins by referencing relevant studies such as Chin. Opt. Lett. 23, 092201- (2025), Light Sci Appl 9, 41 (2020), Chin. Opt. Lett. 21, 071901- (2023), PhotoniX 4, 24 (2023), and others, to enhance the depth and persuasiveness of this discussion section.
4. The schematic diagram in Figure 1d currently lacks an annotation indicating the laser propagation direction. Adding this key information would help readers intuitively understand the process of laser-matter interaction.
5. Could the ICP (Inductively Coupled Plasma) etching process potentially affect the characterisation of the morphology in the laser-modified regions?
6. To my knowledge, standard self-focusing effects typically do not produce a focused beam that propagates strictly back along the original optical path. The typical manifestation involves the formation of periodic structures beyond the focal region along the laser propagation direction. However, the results in Figure 2c show that as the number of pulses increases, the formed structures clearly extend progressively towards the laser incident side. This phenomenon appears similar to results reported in Super-stealth dicing of transparent solids with nanometric precision. Nat. Photon. 18, 799–808 (2024). It is recommended that the authors provide further analysis and explanation for the physical mechanism behind this reverse structure formation.
7. Will the laser repetition rate affect the results? (Chin. Opt. Lett. 22, 013201 (2024))

Author Response

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Reviewer 2 Report

Comments and Suggestions for Authors

In this manuscript, the authors proposed an ultrafast laser multifilament manipulation strategy based on “elliptical Gaussian beam + pulse duration optimization”. They realized long-range ordered SiC multifilaments via elliptical Gaussian beams, reveal ionization/self-trapping mechanisms, and offer a universal method for hard semiconductor deep-subwavelength nanofabrication. In my opining, this idea is interesting and innovative, meanwhile, this This might offer more possibilities in microplasticity. However, before its publication, I still have some doubts. And there are small details should be revised.

Major concerns:

1. This idea is great, but I want to know how to deal with the excessively damaged region and color center region, if we only need the multifilament region.
2. Since our operation is highly precise, can this technology precisely control the position of the multiple wires within the range of 10 micrometers?
3. It is pointed out that the multi-thread quality is at its best at 10 ps. However, this is merely a qualitative assessment of the image, without any quantitative criteria, which makes it lack the rigor of scientific research.

Minor comments:

1. Line 209, “multifilament structure” should be “multifilament structure”.
2. Line 515, “Fig.11” was not mentioned in this manuscript, it should be “Fig.A6”.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

See the file.

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have addressed all concerns. I believe it will attract lots of wide interest and recommend its acceptance. 

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have made satisfactory revisions according to my comments. Thanks.