High-Performance Metamaterial Light Absorption from Visible to Near-Infrared Assisted by Anti-Reflection Coating
Round 1
Reviewer 1 Report
In the manuscript (photonics-2573803) entitled “High-performance Metamaterial Light Absorption from Visible 2 to Near-Infrared Assisted with Anti-reflection Coating”, the authors proposed and demonstrated an ultra-broadband absorber from visible to near-infrared wavelength range by an anti-reflection coating on a conventional metal-insulator-metal metamaterial absorber. With SiO2 and Si3N4 coatings, the absorption bandwidth is increased by 594nm and 1093nm, respectively. Adding an anti-reflection coating is a novel way to improve the performance of metamaterial absorber. This brings an efficient scheme to the community for realizing broadband metamaterial absorber. I strongly recommend its publication on Photonics in the present form. One minor comment is that Eq. (1, 2) are invisible in the submitted pdf file.
Author Response
Please see the attachment R1response_0824.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This study introduces an ultra-broadband material absorber (UBMA) utilizing a Ti-SiO2-Ti metasurface with an anti-reflection coating (ARC). SiO2 and Si3N4 coatings respectively enable optimal impedance matching, achieving 90% absorption bandwidth at 502-1892 nm for SiO2 ARC, and at 561-2450 nm for Si3N4 ARC. The UBMA shows significant enhancement in absorption bandwidth compared to structures with no ARC. In addition to impedance matching, thin-film interference, surface plasmon resonances, and Fabry-Pérot cavity resonance also facilitate absorption. TE and TM modes maintain high absorption across wide incident angles. The corroborated simulation and experiments are interesting, which would allow for scalable, low-cost production and broad applications in energy harvesting. However, a few questions need to be addressed to improve the paper:
1. The equations in the PDF version of the manuscript are currently absent, leaving those sections blank where the equations are expected to appear. This makes it difficult to evaluate the scientific soundness of the paper.
2. If a layer of air is considered in the simulation, it is better to include it in the cross-section illustration in Fig. 1b.
3. The authors state that one of the interference ‘originates from the reflection at the interface of silicon and Ti’. Does the system have silicon (Si)? My understanding is that a Ti/SiO2/Ti with a SiO2 antireflection coating was analyzed in Figure 3. Does the author mean 'the interface of SiC ARC and top Ti layer'?
4. In Figure 5a, the overall features of the absorption of the UBMA with SiO2 coating are similar to the simulation. However, the Si3N4 displays a significant drop in absorption around 1000 nm. Do the authors have any thoughts on this? Maybe it is important to analyze the electric and magnetic field distribution of the Si3N4 ARC as what has been done for SiO2 ARC in Fig.3.
5. The above-mentioned absorption drop is more evident in large incident angles as shown in Fig.5f. Have the authors simulated the angle dependence of the EM field?
Author Response
Please see the attachment R1 response_0824
Author Response File: Author Response.pdf
Reviewer 3 Report
The manuscript presents the results of the development and testing of modern metamaterials with high light absorption.
The research is undoubtedly important, but the design of the Manuscript requires substantial editing.
1. The paragraph (lines 51-71) refers to the results of the work, not to the Introduction and repeats the Annotation very much. The same text is present in the Conclusions.
2. The figures should be placed immediately after the first mention.
3. Formulas (1) and (2) are missing.
4. On Figures 1, 2 along the abscissa axis, not "Lambda" should be written, but "Wavelength".
The methodology is satisfactory, but the measurements of the spectra can be described in more detail.
The literature review and references are satisfactory.
Author Response
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Author Response File: Author Response.pdf
Reviewer 4 Report
The authors proposed and experimentally demonstrated a wide-band metamaterial absorber working from visible to infrared range. The multi-cell configuration was applied to initially expand the absorption bandwidth, which was further broadened by two different anti-reflection coatings of SiO2 and Si3N4. Correspondingly, the bandwidth increase reaches to 594 nm and 1093 nm, respectively. Also, in both cases, the nanostructure can work with a large incident angle for both TE and TM modes. The novelty of this work is well presented, and the working principle is clearly explained. Experimental results can well support the simulations. This work should be attractive to the readers of MDPI Photonics, and I suggest accepting the manuscript after completing the following minor revisions
1) In the introduction, the authors should give a comprehensive overview and discussion about the reported research. Although a comparison is shown in Table. 1, including a discussion in the introduction will make it easier for the reader to get the novelty of the paper.
2)The ARCs well improve the absorption bandwidth, however, the authors didn’t explain why choose SiO2 and Si3N4. A clear explanation should be added in section 2. Design and simulations.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The authors have comprehensively answered my comments. I recommend the publication of the manuscript in its present form.
Reviewer 3 Report
The authors have significantly improved the Manuscript. I recommend this Manuscript for publication in its present form.
Reviewer 4 Report
Accept in present form
