Review Reports - A High-Sensitivity Sensor Based on Insulator-Metal-Insulator Structure

Round 1

Reviewer 1 Report

The authors studied a high-sensitivity sensor based on insulator-metal-insulator structure. This work is interesting and has potential application in surface plasmon resonance biosensor. The manuscript was written well. I would like to recommend this manuscript for publication, after the following concerns are addressed properly.[1] The English of this manuscript needs to be improved further. For example, in Line 21, “220μm/RIU” should be “220 μm/RIU”. There are also similar errors, which should be corrected in the revised manuscript.

[2] Figure 12 shows the sensitivity and FOM achieved by wavelength modulation of the sensor at an incidence angle of 60° and a RI range of 1.33-1.45. The sensitivity and FOM change abruptly when RI is increased in steps of 0.02. So, I strongly suggest the authors to add more data for RI to be 1.33, 1.35, 1.37, 1.39, 1.41, 1.43, and 1.45.

[3] There are some very relevant works on biosensors based on surface plasmon resonance (SPR): Results in Physics 39, 105732 (2022); Opt. Commun. 528, 128993 (2023). These papers can be cited properly to give audience a broader picture of this field.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The Authors propose a theoretical study on a surface plasmon resonance sensor based on insulator-metal-insulator stack. The manuscript is well written, and the results are very interesting.

Here, my comments:

1. The Introduction should be enlarged to take into account also very performing full dielectric structures (see, i.e, Last advances in silicon-based optical biosensors. sensors, 16(3), 285, 2016; Cancer biomarker detection with photonic crystals-based biosensors: an overview. Journal of Lightwave Technology, 39(12), 3871-3881, 2021) and innovative devices that combine dielectric and metal layer (see, i.e, Highly sensitive refractive index sensor based on polymer bragg grating: A case study on extracellular vesicles detection. Biosensors, 12(6), 415, 2022; A compact and ultra high sensitive RI sensor using modal interference in an integrated optic waveguide with metal under-cladding. Sensors and Actuators B: Chemical, 240, 1302-1307, 2017). The Authors should highlight the main bottlenecks of plasmonic or dielectric configurations.

2. For the plasmonic devices, the main problem regards the temperature increase and the losses. In particular, the Authors should estimate how the temperature change and the losses that they take into account in the simulations.

3. Fig.4-5: all the behaviours should be physically justified.

4. The major issue of the manuscript is a lack of a target application. In particular, they report the capability to monitor a RI change of 1.3494-1.3495. To increase the appeal of the manuscript, please report a target analyte with these RI.

Author Response

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Reviewer 3 Report

The authors proposed a plasmonic sensor based on insulator-metal-insulator structure. Although this manuscript is interesting, there are many problems, such as English problems, that need to be carefully addressed:

¾ Why did the authors use the Lorentz-Drude model? The authors are advised to explain this issue in their manuscript.

¾ Can the authors prove these simulation results with three-dimensional simulation?

¾ In the Abstract, it is not clear what the reported abbreviation RIU means. Later in the text becomes clear that this abbreviation.

¾ The fabrication process of the structure should explain by the authors.

¾ In regards to the plasmonic sensors, the authors should mention other configurations in the introduction section such as:

o https://doi.org/10.1016/j.snb.2017.04.064.

o https://doi.org/10.1016/j.ijleo.2021.168466.

o 10.1109/JSEN.2016.2522560.

o https://doi.org/10.3390/nano12193396.

o https://doi.org/10.1016/j.photonics.2018.08.002.

o https://doi.org/10.1002/appl.202200099

¾ The English are poor in this manuscript; there are many English problems and typing errors.

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

The author proposed a theoretical model of a surface plasmon resonance (SPR) biosensor based on the dielectric-metal-dielectric structures. The simulation of the near-field, sensitivity, and Figure of merit (FOM) is also demonstrated in this work. However, several works based on dielectric-metal-dielectric structures have a larger sensitivity of 330µm/RIU [Optics Express 31, no. 3 (2023): 3520-3535]; 400 μm/RIU [Optical and Quantum Electronics 55, no. 5 (2023): 405] than this work. Therefore, I recommend that the manuscript be accepted after undergoing major revisions. My comments are detailed below:

1. What is the novelty of this work apart from the double layer of dielectric-metal-dielectric structures? Could the author put the author’s aims in the introduction section?

2. Several works based on dielectric-metal-dielectric structures have a larger sensitivity of 330µm/RIU [Optics Express 31, no. 3 (2023): 3520-3535]; 400 μm/RIU [Optical and Quantum Electronics 55, no. 5 (2023): 405] than the proposed work. Could the author briefly discuss this in the results discussion section?

3. The author mentions that Figures 4 and 5 are experimental results of electric field mode, sensitivity, and FOM of the multi-dielectric-metal-dielectric structures with different thicknesses of the first and second gold layers. Could the author verify the thickness using the cross-section image of SEM? Furthermore, put those figures into the manuscript to enhance the discussion of the section on the Influence of metal layer thickness.

4. How did the author get the sensitivity data in Figures 4 and 5? Furthermore, where are the experiment reflectance spectra of the resonance frequency of the multi-dielectric-metal-dielectric structures when the thicknesses of the first metal layer and the second metal are 18.8 nm and 20nm?

5. Figure 9 presents the magnetic field in the Z-direction and Y-direction. The comparison between the proposed structure of AgF2-Au-Al2O3-Au-analyte and Al2O3-Au-analyte is fascinating to study. Could the author it in Figure 9?

6. What is the difference between the maximum sensitivity in the experimental result of Figures 4 and 5 and the sensitivity in Figure 12?

7. To help the readers have a more comprehensive understanding of the new research on high-sensitivity biosensors, I suggest supplementing some latest works about folding metamaterials with extremely strong electromagnetic resonance [Photonics Research 10, no. 9 (2022): 2215-2222.], functionality-switchable devices based on dielectric multi-layers integrated with graphene and VO2 [Optics Letters 47, no. 3 (2022): 678-681]; refractive index sensing based on surface plasmon-coupled emission excited by reverse Kretschmann or Tamm structure [Optics Letters 47, no. 19 (2022): 5068-5071]; Surface plasmon resonance gas sensor with a nanoporous gold film [Optics Letters 47, no. 16 (2022): 4155-4158]; floating terahertz metamaterials with extremely large refractive index sensitivities [Photonics Research 9, no. 10 (2021): 1970-1978].

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

All my questions have been addressed properly, and this work can be accepted for publication.

Reviewer 2 Report

The Authors have strongly modified the manuscript according to the Reviewer suggestions.

Reviewer 3 Report

Reviewer 4 Report

The authors have improved their discussion in this manuscript. Furthermore, this manuscript has relevant references and a clear presentation of the simulation. Although the work does not include the experimental data, the purpose of this paper of studying the theoretical sensor model based on numerical has been fulfilled. Therefore, I would like to accept this manuscript.