Flexible Terahertz Metamaterials Absorber based on VO₂

Round 1

Reviewer 1 Report

This work presented a flexible THz metamaterial absorber (MMA) incorporated with phase change material VO₂, and explored the bending and tunable properties of the absorber. It is interesting to maintain more than 92% absorption at 0.24 THz under different bending angles. In addition, the dynamic modulation of THz waves is achieved by relying on the phase change properties of VO₂. I think it would significant for the potential application of flexible THz smart devices. So I recommend a minor revision for this manuscript and it would be accepted for publication in Photonics after addressing these concerns:

 1. The authors need to introduce the current status of research on flexible metamaterials to the reader in the Introduction section.

 2. As a theoretical work, the simulation methods should be given in detail. I would ask the authors to provide more information regarding how they performed the numerical simulation.

3. The authors can highlight the advantages of this work by comparing it with the work of other peers.

 4. The authors mentioned in the caption of Fig. 6 that the conductivity of VO₂ is 10, 100, 1000 and 10000 S/m, but there are only 3 curves in the figure, the authors need to check again.

 5. The manuscript should be thoroughly proofread to avoid typos and grammatical errors. In addition, the reference format needs to be seriously checked.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments on the manuscript

This manuscript presents a flexible Terahertz (THz) tunable metamaterial absorber (MMA) incorporating vanadium dioxide (VO2). The MMA design consists of an I-shaped metamaterial combined with a split ring structure, achieving near-perfect absorption at two frequencies, which are respectively bending insensitive and sensitive. In addition, the absorber's absorption properties can be dynamically modulated by triggering the phase transition of VO2.

The scientific research presented in the manuscript is interesting and provides valuable theoretical insights into dynamic metasurfaces. The technical aspects of the manuscript are solid and well-founded. However, it is noted that the explanation regarding the bending sensitivity or non-sensitivity of different modes lacks clarity, which affects the scientific depth of the work. Despite this, the work is suitable for publication in Photonics, provided the minor issues are addressed.

1.      “Although the MMAs reported can achieve high absorptivity, most of them still have many drawbacks, such as single wave band, narrow receiving angle, fixed resonant frequency and absorption intensity, which greatly limit their practical applications[10-12].” Correct; however, some recent advances in MMAs are missing. [Liang, Yao, et al. "Hybrid anisotropic plasmonic metasurfaces with multiple resonances of focused light beams." Nano Letters 21.20 (2021): 8917-8923; Stewart, Jon W., et al. "Control of Nanoscale Heat Generation with Lithography-Free Metasurface Absorbers." Nano Letters 22.13 (2022): 5151-5157]

2.      Regarding Figure 4a, it is worth noting that the authors observed an intriguing phenomenon in their results: the Q-factor of the resonance mode near 0.4 THz decreases with increasing oblique incident angles. This phenomenon can be attributed to the physics of Bound states in the continuum (BICs). The authors can highlight this point and emphasize its significance, thereby enhancing the scientific value of their work. Since this work is based on an anisotropic plasmonic metasurface, further exploration of the concepts of "BICs+anisotropic plasmonic metasurfaces" in related literature can aid the authors in comprehending the underlying BIC mechanisms.

3.      “Thus, we use the incidence angle to simulate its bending state, next, we will analyze the effects of different incidence angles on the performance of the designed MMA.” The relationship between the angular stability issue and the bending non-sensitivity mentioned in the manuscript lacks clarity. It would benefit the authors to provide additional information or evidence to support their treatment of the bending issue as an angular stability concern. Including references to similar works that address the bending issue in the context of angular stability would strengthen their argument and provide a solid foundation for their approach.

4.      “The simula-tion results indicate that the I shaped metamaterials combined with split ring structure present two resonant absorption peaks at 0.24 THz and 0.46 THz at normal incidence. By contrast, the absorption at 0.24 THz is nearly insensitive to bending, but the absorption at 0.46 THz is bending-sensitive, across a bending angle of 0-50 degrees.” Why? More discussion to support the conclusion, please.

readable

Author Response

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Reviewer 3 Report

The Authors of the manuscript “Flexible terahertz metamaterials absorber based on VO2” propose a tunable metasurface aimed to work as absorber in THz range. The tunability of absorption peaks is activated by operating on the metasurface bending and activation of metallic phase in VO2 inclusions acting as switchers. The Authors base their results on full-wave simulations which give optimal results in terms of absorptivity also as function of the bending and activation of the phase change material.

The paper is substantially clear and provides encouraging outcomes to make the next step for realizing a real metasurface. I recommend the publication provided font size (scales and axis texts) of all figures are homogenized. For instance, Figs. 3(a),(e) and Fig.6 should present scales and texts larger in comparison with the rest of figures. Yet, the bibliography must be revised because some references are not properly cited.

Author Response

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