Tunable Triple Plasmonically Induced Transparency in Triangular Cavities Coupled with an MDM Waveguide

Round 1

Reviewer 1 Report

The manuscript numerically investigated tunable triple plasmonically induced transparency using triangular cavities coupled with a MDM waveguide. The structure proposed is novel and some results are interesting. However, the numerous avoidable technical errors should be corrected. I have listed a few of these concerns below as pointers.

1. In Fig.1(a), the direction of S21- may be wrong.
2. Why is the equilateral triangular side length chosen as L= 484 nm? How does the length L affect the transmission spectra of the structure? Please discuss.
3. In Eq. (2), n is an integer; in Line 86, n = 1,2,3; in Line 150, n is the refractive index. In a paper, a symbol should have only one meaning.
4. A three-level atomic theory is introduced to explain the mechanism of the PIT effect. It is thought that the PIT effect is formed owing to the destructive interference between two pathway (|1>→|2>→|3>→|2> and |1>→|2>). However, how can two channels form triple plasmonically induced transparency? Please further analyze the physical mechanism of triple plasmonically induced transparency.
5. About all-optical switch with PIT. How to control the presence or absence of the upper triangle to realize the all-optical switch? Please discuss.
6. Why is there the highest sensitivity at dip 6 in Fig 5 (a)? Please explain it.
7. In table 1, the sensitivity of 960 nm/RIU may be 933 nm/RIU, also in Line 219.
8. Please give the references cited in the Johnson and Christy model and equation (1).
9. In equation (10), the definition of λ should be given. Does λ in equation (10) and λ_r in equation (2) represent the same parameter?
10. The authors state that there are six resonance wavelengths in the transmission spectra with the upper triangle in Fig. 2(b). What are the characteristics of these resonance wavelengths?
11. The symbol representing the temperature sensitivity is not consistent in the table 1 and in the formula.

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

In this manuscript, the authors proposed to use side-coupled triangle cavities coupled with a plasmonic waveguide to achieve triple PIT. Both numerical simulations by using FDTD and semi-theoretical model of CMT method were used to investigate. They found that the proposed structure can be used as multifunctional sensors. Overall, this manuscript is of some interesting. In my opinion, it can be considered for publication after the following comments are fully addressed:

1, Some important references that are also concerned with PIT and related sensors were missing, which should be cite and discussed in the manuscript to highlight the imact and novelty of this paper, such as Refs.

"Dynamically tunable plasmonically induced transparency in sinusoidally curved and planar graphene layers," Optics Express, 24(16), 17886-17899. (2016).

S Xiao, T Wang, T Liu, X Yan, Z Li, C Xu, Active modulation of electromagnetically induced transparency analogue in terahertz hybrid metal-graphene metamaterials. Carbon 126, 271-278

2, The structural parameters were set as triangular side length L = 484nm, the distance between the triangle and the waveguide D1 = 30nm, and the width of the waveguide W = 50nm. How did the authors choose these parameters especially the triangular length L?

3, The authors failed to give necessary explanation to Eq. (8). In this equation, q expresses the additional phase change of the MDM waveguide and is set as q = 0. Why? To this end, the authors may refer to Ref. Optics Letters, 42(15), 3052-3055. (2017), where the end phase lost is also set as 0 since the field takes the maximum at the edge.

4, The quality of the Figs. 1b, 2b, 4, and 5a should be improved by concentrating the wavelength ranges to smaller ones, e. g, by setting the maximum range of wavelength to about 1100 nm.

5, Only the field distributions of the third order PIT were shown in the manuscript, why not the first two orders?

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

The authors present their theory and illustrate it with an example. The topic is of interest to the community. I recommend Revise and Resubmit. I have a few questions, indicated below, that may improve the clarity of the manuscript.

1- Please try to point out the new items of the work, esp. in the Introduction along a more prominent way.

2. The Introduction itself is rather small, compared to the length of the manuscript. It would be better to increase its size.

3. Please try to be more specific on the particular parameters of Liquid crystal that have been used in the analysis.

4. Which FDTD method has bee utilized and how the authors have incorporated the LQ in the simulation? As thin sheet or as a surface boundary condition? Please be more elaborate.

5. Some additional analysis on the emerging SPP modes would be welcome? Perhaps a more detailed investigated.

6. Some advanced works were ignored and should be considered:

10.1002/aenm.201502588

10.1038/s41557-018-0045-4

10.1093/nsr/nwaa178

10.1016/j.foodchem.2019.125589

10.1108/TR-12-2020-0619

10.1002/asjc.2415

7. Have the authors attempted to fabricate the proposed device? What would be the most challenging issue in the implementation of graphene?

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

All my concerns were answered point-to-point. The manuscript are now acceptable for publication.

Reviewer 3 Report

The Authors have addressed all of my concerns with the original manuscript. The revised manuscript is ready for publication

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.