Effects of Thickness and Grain Size on Harmonic Generation in Thin AlN Films
Round 1
Reviewer 1 Report
Comments and Suggestions for Authorssee attached file
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Author Response
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Author Response File: Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsIn the manuscript, AlN thin films grown on sapphire substrate are studied. Below band gap 3rd harmonics and above band gap 5th harmonics were generated using a Ti:sapphire oscillator running at 800 nm. A strong enhancement of the 5th harmonic signal in forward direction was observed from thicker 39 nm and 100 nm films compared to thinner 8 nm and 17 nm films. For the 5th harmonic generated in backward direction, and also for the 3rd harmonic both in forward and backward directions, only a weak dependence of the harmonic signal on the film thickness was measured. This work is interesting.
The following are comments of the manuscript for further improvements.
1. In the manuscript, the authors presented an analysis of the experimental results. Yet how about the theoretical results？ Please add.
2. Please add the test images in the revised manuscript.
3. The authors said that “the films were investigated by X-ray diffraction and by measuring the 5th harmonic power dependence on the laser polarization.”. What are the advantages and disadvantages of each of these two methods?
Author Response
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Reviewer 3 Report
Comments and Suggestions for AuthorsThe manuscript investigates the effects of AlN film thickness and grain size on the generation of higher order harmonics. Through the analysis of dependence of X-ray diffraction and harmonic signal on laser polarization, the authors effectively correlate the generation of third and fifth harmonics in AlN films with crystal properties and film thickness, and provide a detailed explanation of the dependence of the fifth harmonic on AlN film thickness. However, the current organization of the introduction and conclusion in the manuscript does not adequately highlight the main content and innovative aspects of this research. my comments are given below:
1. The introduction should be more closely aligned with the research purpose of the paper and enhance the logical flow so that readers can clearly comprehend the motivation and aim of the research. It is recommended that authors reorganize the introduction to clearly state the research question and emphasize its significance within the existing body of research.
2. As for the spectrum of harmonic generation, the author only gives Figure 1. Can the author provide the spectrum of harmonic generation including the pumped laser? What is the maximum conversion efficiency of the third harmonic and fifth harmonic?At the same time, the meaning of "Pos" in Figure 1 should be clearly indicated. Also, how can the desired harmonic order be selected and focused by moving the lenses in the device shown in Figure 1?
3. The manuscript reports the use of Atomic Force Microscopy (AFM) to measure the roughness of the AlN thin films, indicating a remarkably low roughness of 0.4 nm. However, the paper does not include AFM images. It is recommended that the authors include AFM images in the manuscript to visually present the surface morphology and roughness of the thin films.
4. For the different thicknesses of AlN films and the grain sizes calculated according to the Scherrer equation, it is suggested that the author present the data in tabular form, which will make the data clearer and easier to compare.
5. It is mentioned in this paper that the reason for the weak dependence of H3 signal on film thickness is related to the AlN band gap. For the structural integrity of this paper, the author should supplement the band gap diagram of AlN film.
6. In Figure 3, the units of the ordinate should be clearly indicated. At the same time, the meanings of "FW" and "BW" in the legend should be clearly explained in the figure note.
7. In Figure 6, the order of the bonds seems inconsistent, in Figure 6(a) it is b5 b3 b1 from the bottom up, while in Figure 6(b) it is b5 b1 b3. The author should check and ensure that the order of bonds in both graphs is consistent to avoid confusion.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
Comments and Suggestions for AuthorsPublish in its present form.
