Simulated Studies of Polarization-Selectivity Multi-Band Perfect Absorber Based on Elliptical Metamaterial with Filtering and Sensing Effect
Round 1
Reviewer 1 Report
The metamaterial concept is masterfully used in this paper to realize a Polarization-sensitive multi-band absorber with a great absorber rate. Additionally, the paper is well-structured and the results look convincing. However, there are some aspects that certainly need improvements before making the final call on this submission. Here are the detailed comments:
1-Please explain the boundary conditions used in Fig.1.
2-What about the fabrication and measurements? Please elaborate on fabrication difficulties.
3-Despite the critical role of metamaterials in this work, they are not suffienetly addressed. The introduction is a bit abrupt and does not adequately umbrella the state-of-the-art in relation to metamaterails in both aspects of manufacturing and application. In terms of their applications, it should be mentioned that metamaterials have been used to develop antenna-senor antenna, as explained in Tunable terahertz filter/antenna-sensor using graphene-based metamaterials.
Metamaterials have effectively been used for beamsteering as explained in: Beam‐steering of microstrip antenna using single‐layer FSS based phase‐shifting surface.
Another application of metamaterials is transmit array as discussed in All-metal wideband metasurface for near-field transformation of medium-to-high gain electromagnetic sources. Metamatrials have been widely employed sensing effects in envoronemnt as explained in: Advancements and artificial intelligence approaches in antennas for environmental sensing.
Metamaterials also are used as spatial filters, as demonstrated in Single-layer ultra-wide stop-band frequency selective surfaces using interconnected square rings. The authors should demonstrate that metamaterials are very important components in the future of wireless communication and it can only be done by referring to their various applications as stated above.
4-Please elaborate on the simulation procedure and give more details about the simulation setup.
5-Please highlight the novelty in the Abstract.
6-One important aspect missing in this paper is about manufacturing metamaterials. Almost all metamaterials mentined in this paper are printed metamaterials. While metamaterials can be all-dielectric and all-metal as well. it needs to be mentioned that metamaterials can be made of all-dielectric materials such as Recent and emerging applications of Graphene-based metamaterials in electromagnetics. Metamaterials can be made of all-metal components as explained in : All-metal wideband frequency-selective surface bandpass filter for TE and TM polarizations. They also can be made of printed layers. All THREE categories (i.e. all-dielectric, printed layers, and all-metal) should be included in the Introduction with some relevant references.
7-Results and discussion: Please explain the mechanism you captured the electric field.
8- I was wondering how the bandwidth can potentially be increased.
9-Please also include the absorber published in 2023. The following is one relevant that can be included:
M Norouzi et al, “3D metamaterial ultra-wideband absorber for curved surface”, Scientific Reports 13 (1), 1043, 2023.
In summary:
The important application of metamaterials (antenna-sensor, spatial electromagnetic filtering, beamsteering, transmit array, reconfiguring radiation patterns) should be mentioned with relevant refs.
More explanation on design/analysis as commented above.
The 3 categories of metamaterials (all-dielectric and all-metal, and printed layers)
More clarification on the simulation set-up.
Argument on fabrication
Author Response
Response to the comments of the reviewer 1:
General comments: The metamaterial concept is masterfully used in this paper to realize a Polarization-sensitive multi-band absorber with a great absorber rate. Additionally, the paper is well-structured and the results look convincing. However, there are some aspects that certainly need improvements before making the final call on this submission.
We sincerely thanks for your careful readings of our manuscript and very useful and helpful suggestions.
Question 1: Please explain the boundary conditions used in Fig.1.
Answer: In simulation, the boundary conditions are periodic in and directions, while an open boundary is used in the direction.
----Please refer to line 10 - line 15 on Page 3.
Question 2: What about the fabrication and measurements? Please elaborate on fabrication difficulties.
Answer: Compare with previous works [Appl Phys Lett 2017;110(10):101908], the geometric parameters are suitable for fabrication and measurements. Therefore, the Focused Ion beam (FIB) and thermal evaporation methods can be used to fabricate the Ag-SiO2-Ag layer with elliptical nano-slit. However, the size of elliptical nano-slit is too small for us, so it is difficult to prepare samples in a short time with our working conditions.
Question 3: Despite the critical role of metamaterials in this work, they are not suffienetly addressed. The introduction is a bit abrupt and does not adequately umbrella the state-of-the-art in relation to metamaterails in both aspects of manufacturing and application. In terms of their applications, it should be mentioned that metamaterials have been used to develop antenna-senor antenna, as explained in Tunable terahertz filter/antenna-sensor using graphene-based metamaterials.
Metamaterials have effectively been used for beamsteering as explained in: Beam‐steering of microstrip antenna using single‐layer FSS based phase‐shifting surface.
Another application of metamaterials is transmit array as discussed in All-metal wideband metasurface for near-field transformation of medium-to-high gain electromagnetic sources. Metamatrials have been widely employed sensing effects in envoronemnt as explained in: Advancements and artificial intelligence approaches in antennas for environmental sensing.
Metamaterials also are used as spatial filters, as demonstrated in single-layer ultra-wide stop-band frequency selective surfaces using interconnected square rings. The authors should demonstrate that metamaterials are very important components in the future of wireless communication and it can only be done by referring to their various applications as stated above.
Answer: The importance of metamaterials have been demonstrate.
-----Please refer to line 35-line 38 on page 1.
Question 4: Please elaborate on the simulation procedure and give more details about the simulation setup
Answer: The perfect absorption can be simulated by the Frequency Domain Solver based on CST Microwave Studio. Here, the minimum edge length is 2.67 nm, the maximum edge length is 158.53 nm, and the number of mesh cells is 66322. All the designs guarantee the accuracy of simulation results.
- ----Please refer to line 10 - line 15 on Page 3.
Question 5：Please highlight the novelty in the Abstract.
Answer: The novelties of the presented absorber are shown in the abstract.
-----Please refer to line 15 - line 24 on Page 1.
Question 6: One important aspect missing in this paper is about manufacturing metamaterials. Almost all metamaterials mentined in this paper are printed metamaterials. While metamaterials can be all-dielectric and all-metal as well. it needs to be mentioned that metamaterials can be made of all-dielectric materials such as Recent and emerging applications of Graphene-based metamaterials in electromagnetics. Metamaterials can be made of all-metal components as explained in: All-metal wideband frequency-selective surface bandpass filter for TE and TM polarizations. They also can be made of printed layers. All THREE categories (i.e. all-dielectric, printed layers, and all-metal) should be included in the Introduction with some relevant references.
Answer: The manufacturing metamaterials have been discussed and included in the introduction with some relevant references.
-----Please refer to lines 35- 38 on Page 2
And lines 11-13 on Page 10
Question 7: Results and discussion: Please explain the mechanism you captured the electric field.
Answer: To analyze the physical mechanism of the dual-band perfect absorption, we set up electric field monitors at 337.6 THz, 360.5 THz, 326 THz, and 366 THz, respectively. Then the three-dimensional electric field vectors could be stored. In order to better analyze the electric field distribution on elliptical nano-slits, we project the electric field distribution onto the xoy plane [Fig. 3].
-----Please refer to line 18 -line 22 on Page 4.
Question 8: I was wondering how the bandwidth can potentially be increased.
Answer: Figures 5 (c) and 6 (c) indicate that the intensity of the absorption peak remains roughly the same both for TE and TM-polarized waves, when the thickness t increase from 30 nm to 120 nm. By contrast, the absorption peaks shift from 337 THz to 301 THz for TE-polarized waves, when a increase from 43 nm to 83nm Fig. 5(d) and 6(d). Meanwhile, the absorption peaks shift from 337 THz to 301 THz, when a increase from 0 nm to 83 nm. To sum up, we can broaden the absorption effect by stacking elliptic nanoslit metal layers with different a, i.e. the bandwidth covers from 301 THz to 337 THz.
-----Please refer to lines 30 on page 6- line 4 on Page 7.
Question 9: Please also include the absorber published in 2023. The following is one relevant that can be included:
M Norouzi et al, “3D metamaterial ultra-wideband absorber for curved surface”, Scientific Reports 13 (1), 1043, 2023.
Answer: The absorber published in 2023 and discussions have been added to the revision.
-----Please refer to reference [5], [22], [41], [42].
Author Response File: 
Author Response.docx
Reviewer 2 Report
Wang et al. proposed a silver-made elliptical nano-slits based multi-band polarization-sensitive absorber. The proposed absorber provides a good absorption response for both TE and TM polarizations. My comments/questions/suggestions for the authors are listed below.
I. Make a consistency in writing as I found these words written in two ways like Dual-band and dualband, narrow-band and narrowband, multi-layer and multilayer, nano-slit and nanoslit etc.
II. Please write et al. instead of et. al.
III. Structure design and method section line 4, spellings of thickness.
IV. Instead of writing Sio2 please write -SiO2
V. The novelty and Significance of the work is not clear in the abstract. I would advise you to re-write it, considering why we need such dual-band absorbers. Why is this THz band important etc.?
VI. The literature is not complete and updated; authors must update it and also include and discuss works on different other metals like Nickel (doi.org/10.1364/OE.446423), GST (doi.org/10.1002/lpor.202200364); Al-doped ZnO (doi.org/10.1021/acsphotonics.7b00991), tungsten (doi.org/10.1038/s41598-018-20748-9), Vanadium Nitride (doi.org/10.1016/j.mtcomm.2023.105416), TiN (doi.org/10.3390/nano8070485), and etc.
VII. In the introduction section: authors mentioned, “In recent years, different kinds of metamaterials configured by dielectric-metal materials, dielectric-function materials, or metal-dielectric-function materials”. Authors should use some better terminology instead of dielectric-function materials and metal-dielectric-function materials.
VIII. Result and Discussion section: “Here, the anisotropic of the elliptical nano-slits results in selective absorption of TE and TM-polarized, and then the reflectances are also selective.” Use anisotropy or anisotropic effect.
IX. I would suggest authors should include a little more explanation related to Power loss density in the revised manuscript.
X. In Results and Discussion section: Authors mentioned, “In addition, the transmittances (T) are zero for TE and TM-polarized waves, attribute to the surface effect depth of TE and TM-polarized waves being less than 150 nm [Fig. 2(a)]” What is this surface effect depth? Please provide more details about it.
Author Response
Response to the comments of the reviewer 2:
General comments: Wang et al. proposed a silver-made elliptical nano-slits based multi-band polarization-sensitive absorber. The proposed absorber provides a good absorption response for both TE and TM polarizations. My comments/questions/suggestions for the authors are listed below.
We sincerely thanks for your careful readings of our manuscript and very useful and helpful suggestions.
Question 1: Make a consistency in writing as I found these words written in two ways like Dual-band and dualband, narrow-band and narrowband, multi-layer and multilayer, nano-slit and nanoslit etc.
Answer: We have made a consistency in writing, and we write narrow-band, dual-band, multi-layer, and nano-slit instead of narrowband, dualband, multilayer and nano-slit.
Question 2: Please write et al. instead of et. al.
Answer: We have write et al. instead of et. al.
Question 3: Structure design and method section line 4, spellings of thickness.
Answer: The spellings of thickness have been revised.
Question 4: Instead of writing Sio2 please write -SiO2.
Answer: We have write SiO2 instead of Sio2
Question 5: The novelty and Significance of the work is not clear in the abstract. I would advise you to re-write it, considering why we need such dual-band absorbers. Why is this THz band important etc.?
Answer: We have re-write the abstract, and the novelty and significance of the work are shown in the abstract.
-----Please refer to line 15 - line 24 on Page 1.
Question 6: The literature is not complete and updated; authors must update it and also include and discuss works on different other metals like Nickel (doi.org/10.1364/OE.446423), GST (doi.org/10.1002/lpor.202200364); Al-doped ZnO (doi.org/10.1021/acsphotonics.7b00991), tungsten (doi.org/10.1038/s41598-018-20748-9), Vanadium Nitride (doi.org/10.1016/j.mtcomm.2023.105416), TiN (doi.org/10.3390/nano8070485), and etc.
Answer: We have update the literature to the revision.
-----Please refer to line 27 - line 30 on Page 2.
Question 7: In the introduction section: authors mentioned, “In recent years, different kinds of metamaterials configured by dielectric-metal materials, dielectric-function materials, or metal-dielectric-function materials”. Authors should use some better terminology instead of dielectric-function materials and metal-dielectric-function materials.
Answer: The dielectric-metal materials, dielectric-function materials, metal-dielectric-function materials are instead of substrate-metallic materials, substrate-tunable dielectric materials, metal-substrate-tunable dielectric materials.
-----Please refer to line 31 - line 33 on Page 1.
Question 8: Result and Discussion section: “Here, the anisotropic of the elliptical nano-slits results in selective absorption of TE and TM-polarized, and then the reflectances are also selective.” Use anisotropy or anisotropic effect.
Answer: We have use anisotropy instead of anisotropic.
Question 9: I would suggest authors should include a little more explanation related to Power loss density in the revised manuscript.
Answer: We have include some explanation related to Power loss density in the revised manuscript.
-----Please refer to line 9 - line 15 on Page 5
Question 10: In Results and Discussion section: Authors mentioned, “In addition, the transmittances (T) are zero for TE and TM-polarized waves, attribute to the surface effect depth of TE and TM-polarized waves being less than 150 nm [Fig. 2(a)]” What is this surface effect depth? Please provide more details about it.
Answer: Here the “surface effect depth” is “skin depth” The discussion has been provided “Owing to the skin depth of electromagnetic waves, the transmission distances in Ag film are less than 150 nm for the high frequency TE and TM-polarized waves. As a result, the transmittances (T) are zero for TE and TM-polarized waves.”
-----Please refer to line 1 - line 4 on Page6
Author Response File: Author Response.docx
Reviewer 3 Report
The comments are in the file.
Comments for author File: 
Comments.pdf
Author Response
Response to the comments of the reviewer 3:
General comments: In the last few years, a new branch of electrodynamics has begun to develop rapidly - the electrodynamics of negative-index metamaterial. This is what the work “Polarization-sensitive multi-band perfect absorber based on elliptical metamaterial with filtering and sensing effect” by Ying-Hua Wang et. al. However, before recommending the manuscript for publication, we would like the authors to comment on the following issues:
We sincerely thanks for your careful readings of our manuscript and very useful and helpful suggestions.
Question 1: In the title, I would not use the word “sensor” twice and its derivatives (sensitive, sensing). And in general. the work is devoted to modeling/numerical analysis, so I would indicate this in the title of the manuscript.
Answer: The title has been set as “Simulated studies of polarization-dependent multi-band perfect absorber based on elliptical metamaterial with filtering and sensing effect” indicating the modeling/numerical analysis.
-----Please refer to the title on Page6
Question 2: It would seem that there are simpler ways to organize absorption (10.1016/j.oplastec.2022.108873) and polarization control (10.1364/OME.428047; 10.1007/s00138-018-0962-7). Therefore, with this phrase (“As a result, the elliptical perfect absorber provides promising
potential applications in imaging, filtering, and infrared detection.”) I would be more careful. Why did the choice fall on the metamaterial indicated in the article, which will not be easy to make in comparison with elements made by femtosecond fabrication?.
Answer: The metamaterial indicated in the article are subwavelength structures, and the size of the elliptical nano-slit can be controlled flexibly, which can realize absorption and polarization selection simultaneously. As a result, elliptical perfect absorber provides promising potential applications in imaging, filtering, and infrared detection possibilities for the research of micro and nano optical devices and their applications on chips.
-----Please refer to line 2 - line 4 and line 35-line 36 on Page 2
Question 3: Why was such an absorber model chosen in section two? What is the novelty of the presented
absorber?.
Answer: The elliptical nano-slits present anisotropic effect for TE and TM-polarized waves, As a result, the perfect absorption proposed in this work is polarization-sensitive, which leads to the filtering effect of TE wave and TM. So we chose the absorber model to study the absorption and filtering characteristics.
The novelties of the presented absorber are shown in the abstract.
-----Please refer to line 15 - line 24 on Page 1.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
can be accepted now
Reviewer 3 Report
Continue in the same spirit.
