Laser 3D Printing of Inorganic Free-Form Micro-Optics

Round 1

Reviewer 1 Report

Authors present interesting work concerning manufacturing of free-form micro-optics out of transparent and pure inorganic glasses. During reading of manuscript I have not found answer on the following questions:

• The authors use the abbreviation LWD. Unfortunately, I have not found an explanation of what it means at text of manuscript.
• In chapter 2.1 only the commercial name of the preparation used is given, but there is no information what it contains.
• The description of the micro-lens with support manufacturing process needs to be supplemented. The present one is too general and reading it I don't know how the micro-lens support was made.
• What does omega zero mean in equation 1?
• Were the photos in figure 4 taken at the same magnification? Adding a status bar to your photos would be the best answer to this question.
• Can the authors say something specific about the refractive index of the produced micro-lens? If they cannot determine it directly, then maybe indirectly by comparing the properties / structure of e.g. coatings of the material from which the micro-lens was made with the properties / structure of the micro-lens.
• Are the results presented in Figure 5 obtained by the authors of the paper? I am asking because in Chapter 2 there is no mention of the manufacture of the presented micro-lenses (see temperature).
• Have the authors optimized the temperature and time of the calcination process?
• What does the abbreviation VU LRC stand for in acknowledgments?
• Are you sure this work is conceptual work?

Concluded, the manuscript after major revision can be considered for publication in the Photonics.

Author Response

Reviewer 1

Authors present interesting work concerning manufacturing of free-form micro-optics out of transparent and pure inorganic glasses. During reading of manuscript I have not found answer on the following questions:

• The authors use the abbreviation LWD. Unfortunately, I have not found an explanation of what it means at text of manuscript.

Indeed, the common abbreviation LDW standing for laser direct write was missed, thus we included it both in the Abstract and Introduction.

• In chapter 2.1 only the commercial name of the preparation used is given, but there is no information what it contains.

Again, the remark is correct as SZ2080^TM even though widespread and trademarked commercially available resin it is still not obvious for everyone – explained, referenced, and reasoned why specifically this material was chosen for experiments.

• The description of the micro-lens with support manufacturing process needs to be supplemented. The present one is too general and reading it I don't know how the micro-lens support was made.

Taken into account and amended – the description was supplemented with the relevant details and the Figure 2  was updated to make it additionally more clearer visually.

• What does omega zero mean in equation 1?

Nominal beam waste radius – updated.

• Were the photos in figure 4 taken at the same magnification? Adding a status bar to your photos would be the best answer to this question.

The Figure 4 was updated with extra row showing the scale of the lens, imaged target value and imaging of the object.

• Can the authors say something specific about the refractive index of the produced micro-lens? If they cannot determine it directly, then maybe indirectly by comparing the properties / structure of e.g. coatings of the material from which the micro-lens was made with the properties / structure of the micro-lens.

Estimated measured value average was provided to be n ≈ 1.609, which is comparable to the reported value of non-structured material (1.617).

• Are the results presented in Figure 5 obtained by the authors of the paper? I am asking because in Chapter 2 there is no mention of the manufacture of the presented micro-lenses (see temperature).

The Figure 5 is of the same group of Author and the description of fabrication parameters was provided. The shown benchmarking structures were made for the pure demonstration purpose and with different parameters, including the heat-treatment protocol. The manufacturing parameters were provided and the figure amended accordingly.

• Have the authors optimized the temperature and time of the calcination process?

Specifically for this study a systematic investigation was not carried out, but we use empirically obtained values from the other experiments. Thus, in this sense – yes, optimized.

• What does the abbreviation VU LRC stand for in acknowledgments?

Vilnius University Laser Research Center – acronym of the first and corresponding Author’s institution. In order to be definitely clear – a city and country next to it was added. Also next to IESL-FORTH for the sake of keeping the same formatting.

• Are you sure this work is conceptual work?

We prove the concept of the LDW 3D nanolithography of hybrid materials combined with calcination post-processing as a novel route for the nanoscale additive manufacturing of transparent inorganics for micro-optical applications. The concept is supported by the dedicated experiment, thus we believe it can be claimed as a conceptual validation study.

Concluded, the manuscript after major revision can be considered for publication in the Photonics.

We thank Reviewer 1 for its positive evaluation and accurate questions / remarks, which makes the manuscript more understandable and self-sustainable for the reader and potential reproducibility of the findings.

The corrections in the Manuscript corresponding to the addressed comments by the Reviewers are marked in red and the other amendments/additions are marked in blue.

Reviewer 2 Report

This manuscript reported laser 3D printing of inorganic free-form micro-optics. The developed methodology offers the production of highly resilient 3D micro-optical components. The manuscript is well-written and organized. I recommend publication after a minor revision.

 

1. Can the authors add more discussions on the thermal effect of the hybrid organic-inorganic material SZ2080TM?
2. How about the optical performance of SZ2080TM micro-lenses?
3. After the heat treatment, is there any fissure on the structure?
4. Are the structures fabricated by multi-photo absorption?
5. In the introduction section, the authors should add more discussions on the advantages of The following references may be helpful, such as Nature Reviews Materials 2018, 3, 84; Advanced Materials 2016, 28, 8328; Advanced Materials 2019, 32, 1901981; Optics Letters 2020, 45, 113.

Author Response

This manuscript reported laser 3D printing of inorganic free-form micro-optics. The developed methodology offers the production of highly resilient 3D micro-optical components. The manuscript is well-written and organized. I recommend publication after a minor revision. 

1. Can the authors add more discussions on the thermal effect of the hybrid organic-inorganic material SZ2080TM?

A Discussion subsection 4.1 was created for substantially describing and discussing the thermal effects of SZ2080 and its application in micro-optics.

1. How about the optical performance of SZ2080TM micro-lenses?

We are not sure of what exactly is being asked? The transparency and imaging performance of the micro-lenses was characterized as qualitative and quantitative parameters. The exact refractive index will be measured in the future as the current limitation of the experimental setup did not allow to do it very precisely and it seems like could be matching with the values available in the literature (for 2D, not for 3D case though). We anticipate the effective refractive index may vary depending on the specific geometry of the 3D micro-optical components. A speculative sentence regarding this was added to the very end of the Conclusions.

1. After the heat treatment, is there any fissure on the structure?

No, no fissure was noticed during all of the carried experiments. We believe that during the elevated temperatures the mater softens and is not fragile even being completely inorganic. A comment stressing it was added to the Conclusion Item 1.

1. Are the structures fabricated by multi-photo absorption?

We do not study or claim any of the specific light matter interactions determining the fabrication. But yes, this is correct - the performed lithography is based on thresholded light-matter interaction which is a signature of non-linear (multi-photon) absorption. From our own experience and available literature it also might be some linear absorption, avalanche ionization and even thermal effect contributing to the ultra-localized polymerization. An extra comment on that was added to the Section 2.3.

1. In the introduction section, the authors should add more discussions on the advantages of The following references may be helpful, such as Nature Reviews Materials 2018, 3, 84; Advanced Materials 2016, 28, 8328; Advanced Materials 2019, 32, 1901981; Optics Letters 2020, 45, 113.

We thank Reviewer 2 for constructive proposal and include the mentioned references accordingly while outlooking the future perspective (within the Discussion Section).

 

The corrections in the Manuscript corresponding to the addressed comments by the Reviewers are marked in red and the other amendments/additions are marked in blue.

 

Round 2

Reviewer 1 Report

Thank you for your responses to the questions presented in the review and correction in manuscript. I have one more note left, the work lacks information on the wavelength for which the refractive index is determined.

I recommend the work for publication in the Photonics journal.

Author Response

Thank you for your responses to the questions presented in the review and correction in manuscript. I have one more note left, the work lacks information on the wavelength for which the refractive index is determined.

A precise note! Even though it was mentioned in the 2.6 Performance evaluation sub-section as used for imaging, but not stressed directly that the very same equipment was used for refractive index measurement too. Now we have stated it clearly and also promptly repeat it in the 3. Results section to avoid any ambiguity. At the same time it explains the possible uncertainty and the need to confirm it using alternative technique(s) in the future.

The updated text is highlighted in the manuscript.

 

I recommend the work for publication in the Photonics journal.

Thank You for reconsidering, noting the missing detail and in general positive evaluation.