Numerical Simulation and Experimental Investigation of Single-Point Picosecond Laser Ablation inside K9 Glass

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This article offers a vector diffraction model which describes the internal electric field inside the k9 glass with a variable numerical aperture objective. Besides, the ablated areas consist of numerous small ablated dots are observed. The following problems need to be modified before publication.

 

1、  Please standardize the spell and unit of density in Table 1.

2、  The white texts on Figure 8 are not clear and intuitive, and a different color is recommended.

3、  Please be consistent in writing whether variables are italicized or not in the article, and whether the equals sign is spaced twice or not when writing assignments for variables should also be consistent throughout the article.

4、  Line 336, the article states that the calculated power is 1.2MW, but it also says, “only the peak power at a single-pulse energy of Q=5uJ was lower than the critical power threshold”. Is there a writing error here?

5、  The description of Figure 9 says that the SEM map is in the red box, but only the red box is seen in Figure 9a, so please further retouch the image with its description.

Comments on the Quality of English Language

This article offers a vector diffraction model which describes the internal electric field inside the k9 glass with a variable numerical aperture objective. Besides, the ablated areas consist of numerous small ablated dots are observed. The following problems need to be modified before publication.

 

1、  Please standardize the spell and unit of density in Table 1.

2、  The white texts on Figure 8 are not clear and intuitive, and a different color is recommended.

3、  Please be consistent in writing whether variables are italicized or not in the article, and whether the equals sign is spaced twice or not when writing assignments for variables should also be consistent throughout the article.

4、  Line 336, the article states that the calculated power is 1.2MW, but it also says, “only the peak power at a single-pulse energy of Q=5uJ was lower than the critical power threshold”. Is there a writing error here?

5、  The description of Figure 9 says that the SEM map is in the red box, but only the red box is seen in Figure 9a, so please further retouch the image with its description.

Author Response

Comments 1: Please standardize the spell and unit of density in Table 1.

Response 1: Thank you for pointing this out, the spelling of “density” and its unit in Table 1 has been corrected to “Density” and “g/cm³”, also, the correction were highlighted in the text. In p6, line202.

 

Comments 2: The white texts on Figure 8 are not clear and intuitive, and a different color is recommended.

Response 2: Thank you for your suggestion, in p10, line309, the text color in Figure 8 has been changed to a more distinct black.

 

Comments 3: Please be consistent in writing whether variables are italicized or not in the article, and whether the equals sign is spaced twice or not when writing assignments for variables should also be consistent throughout the article.

Response 3: Thank you for your suggestion, all variables in the text are italicized. Spaces around the equals sign in variable assignments have been uniformly removed.

 

Comments 4: Line 336, the article states that the calculated power is 1.2MW, but it also says, “only the peak power at a single-pulse energy of Q=5uJ was lower than the critical power threshold”. Is there a writing error here?

Response 4: Thanks for pointing this out. We have made revisions to this passage：The calculated value of P_cr was 1.2MW. In the experiment, when the single-pulse energy Q=5μJ with 10ps pulse width, the peak power was 0.5MW, which was lower than the critical power threshold. It is highlighted in the text. In p10, line334.

 

Comments 5: The description of Figure 9 says that the SEM map is in the red box, but only the red box is seen in Figure 9a, so please further retouch the image with its description.

Response 5: Thanks for pointing this out. In the description of Figure 9, the SEM image in the red box is now accompanied by the modifier “in Figure 9(a)”. In p11, line364.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

This paper takes the common optical material K9 as the target material to study the interior ablated effect by picosecond laser. The vector diffraction methed were ultilized in the calculated model. The internal electric field and the temperature field models were set up. The temperature field distribution results were given out.The experients verified the thereotical simulation results. The key factor was the laser focal position in the material. The multiple ablated dots phenomenon is interesting.The possible forming mechanism such as nonlinear refractive index of material inducing spherical distortion of the phase front and laser self-focusing are  speculated.The research works includes element analysis in the interior zone of the laser and material interaction,to further strengthen some explanations. 

Suggestion:

1.The used laser type should be expressed in the title.

2. “its manufacturing cost is significantly low”, should means exactly, for its optical element manufacturing cost is significantly low,or the meterial itself, or other?

3. “such as for laser anti-reflective coatings”, maybe not expressed exactly in meanings.

4.“different pulse repetition frequencies”, should be repetition rate.

5.p3,first paragraph, “the lattice”, should be indicated as the material lattice.

6.p3, dnom, nom should be written in subscript.

7.The K9 meterial manufacturer or purchaszing company should be written out.

8. p6,The laser focal depth is adjusted by controlling the height of the objective lens.Is it focus position or disfocusing distance？

9. Which was more exact in meanning,diffraction dot or the diffraction beam?

10.How does the material nonlinear absorption mechanism be expressed in the simulation model equation formula, even with time parameter?

11.p14, line 334, the formula have the same unit in the both sides of the equal sign?

12. In paragraph 12, line 397, “it can no longer cause self-focusing”, can be better rewritten as “it cannot cause self focus any more”. 

12. “the upper surfaces of the two ablated area”, should be changed as the upper vertex of the two ablated areas.

13. Maybe the foci position affection on the ablation zone shape, could be an indirect parameter. The direct affection factor is the laser energy distribution along the beam propagation in the material. 

Comments on the Quality of English Language

The paper English expression is well to be understood by the readers.

Author Response

Comments 1: The used laser type should be expressed in the title.

Response 1: We agree with this comment, “picosecond” has been added to the title. In p1, line3.

 

Comments 2: “its manufacturing cost is significantly low”, should means exactly, for its optical element manufacturing cost is significantly low or the material itself, or other?

Response 2: Thank you for your suggestion, the sentence “Moreover, the manufacturing cost of K9 glass material is significantly low” has been deleted. In p2, line34.

 

Comments 3: “such as for laser anti-reflective coatings”, maybe not expressed exactly in meanings.

Response 3: Thank you for your suggestion, the sentence “such as laser anti-reflective coatings” has been deleted. In p2, line36.

 

Comments 4: “different pulse repetition frequencies”, should be repetition rate.

Response 4: Thank you for your suggestion, we agree with this comment, the phrase “repetition frequencies” has been changed to “repetition rates” and the same issue has been corrected in other instances as well. In p2, line74.

 

Comments 5: p3,first paragraph, “the lattice”, should be indicated as the material lattice.

Response 5: Thank you for your suggestion, we agree with this comment, the phrase “the lattice” has been changed to “the material lattice”. In p3, line103.

 

Comments 6: p3, dnom, nom should be written in subscript.

Response 6: Thank you for your suggestion, the “dnom” has been corrected to “d_nom”. In p3, line119.

 

Comments 7: The K9 meterial manufacturer or purchaszing company should be written out.

Response 7: Thank you for your suggestion, the manufacturer of the K9 glass material has been annotated, and was highlighted in the text. In p5, line183.

 

Comments 8: p6, The laser focal depth is adjusted by controlling the height of the objective lens. Is it focus position or disfocusing distance?

Response 8: Thank you for your suggestion, we agree with this comment, the phrase “laser focal depth” has been changed to “laser focal position”. In p6, line198.

 

Comments 9: Which was more exact in meaning, diffraction dot or the diffraction beam?

Response 9: Thank you for your suggestion, we agree with this comment, the phrase “diffraction dot” has been changed to “diffraction beam”. In p7, line245, line247.

 

Comments 10: How does the material nonlinear absorption mechanism be expressed in the simulation model equation formula, even with time parameter?

Response 10: Material nonlinear absorption mechanism is not directly expressed in the simulation model equation formula. However, during the simulation process, different nonlinear absorption coefficients were chosen based on varying single-pulse laser energies. The relationship between the material's nonlinear absorption coefficient and the picosecond laser single-pulse energy was obtained from the reference[11]. The nonlinear absorptivity increases with increasing energy of the laser pulse.

 

Comments 11: p14, line 334, the formula have the same unit in the both sides of the equal sign?

Response 11: For Equation 23, to make the calculation results more accurate, “” has been changed to “”, in p10, line332. The units on both sides of the equation are consistent. Here, n_a refers to the nonlinear refractive index coefficient, with units of cm²/W.

 

Comments 12: In paragraph 12, line 397, “it can no longer cause self-focusing”, can be better rewritten as “it cannot cause self focus any more”. 

Response 12: Thank you for your suggestion. “it can no longer cause self-focusing” has been changed to “it cannot cause self focus any more”. In p12, line395.

 

Comments 13: “the upper surfaces of the two ablated area”, should be changed as the upper vertex of the two ablated areas.

Response 13: Thank you for your suggestion. “the upper surfaces of the two ablated area” has been changed to “the upper vertex of the two ablated areas”. In p13, line408.

 

Comments 14: Maybe the foci position affection on the ablation zone shape, could be an indirect parameter. The direct affection factor is the laser energy distribution along the beam propagation in the material. 

Response 14: The distance from the focal point to the material surface still has a direct impact on the energy distribution, primarily affecting the distribution along the optical axis. The deeper the focus, the longer the focused spot along the optical axis, leading to a more dispersed energy distribution.

 

Comments on the Quality of English Language

Comments: The paper English expression is well to be understood by the readers.

Response: Thank you very much for your help.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

The article presents a well-detailed study on the simulation of laser processing in K9 glass using a vector diffraction model. The creation of the simulation and the results are explained clearly and consistently. However, there are a few areas where the clarity and comprehensiveness of the text can be improved. I propose the following corrections and additions for consideration: 

Please review and correct minor typographical errors throughout the manuscript. For instance, on line 117-120, the subscript notation for variables appears inconsistent (example: "n₁" on line 117, "n₂" on line 118, and "d_nom" on line 120). Ensuring consistent formatting will enhance readability.

I recommend adding a table of variable abbreviations to Table 1. This table should include commonly used variables such as the refractive index (n), absorption coefficient (𝛼), etc. This addition will help readers quickly reference and understand the variables used in your study.

The study employs two different focusing objectives with numerical apertures (NA) of 0.4 and 0.6. However, there is a discrepancy in the display methods used for these objectives as shown in Figures 8 and 11. For NA 0.4, both SEM and DEM images are used, whereas for NA 0.6, they are not. Providing an explanation for this difference will enhance the reader's understanding of the methodology and its implications on the results. 

Ensure that terminology and notation are consistent throughout the manuscript. This includes the use of abbreviations, symbols, and terms.

Author Response

Comments 1: Please review and correct minor typographical errors throughout the manuscript. For instance, on line 117-120, the subscript notation for variables appears inconsistent (example: "n1" on line 117, "n2" on line 118, and "dnom" on line 120). Ensuring consistent formatting will enhance readability.

Response 1: Thank you for pointing this out. We agree with this comment. Therefore, the term “dnom” has been corrected to “d_nom”. In p3, line119.

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Comments 2: I recommend adding a table of variable abbreviations to Table 1. This table should include commonly used variables such as the refractive index (n), absorption coefficient (?), etc. This addition will help readers quickly reference and understand the variables used in your study.

Response 2: Thank you for pointing this out. We agree with this comment. The abbreviation of commonly used variables has been added to Table 1. In p6, Tabel1.

 

Comments 3: The study employs two different focusing objectives with numerical apertures (NA) of 0.4 and 0.6. However, there is a discrepancy in the display methods used for these objectives as shown in Figures 8 and 11. For NA 0.4, both SEM and DEM images are used, whereas for NA 0.6, they are not. Providing an explanation for this difference will enhance the reader's understanding of the methodology and its implications on the results. 

Response 3: Thank you for pointing this out. We agree with this comment. We conducted experiments using two types of objective lenses with different NA, and observed their differences in internal ablation of K9 glass. The comparison of the morphology of ablation areas under two different numerical apertures has been added, which is highlighted in the text. The ablation areas are located inside the material. under the same experimental parameters, there exhibits a longer axial length but smaller lateral dimensions at NA=0.6, the ablation areas obtained are not on the same plane. Therefore, compared to SEM method, optical microscopy can clearly express laser ablation area. In p12, line397 to line 401.

 

Comments 4: Ensure that terminology and notation are consistent throughout the manuscript. This includes the use of abbreviations, symbols, and terms.

Response 4: Thank you for pointing this out. We agree with this comment. The terminology and notation, including abbreviations, symbols, and terms, have been thoroughly checked and confirmed to be consistent throughout the manuscript.

 

Author Response File: Author Response.docx