Two-Dimensional Dynamic Beam Steering by Tamm Plasmon Polariton
Round 1
Reviewer 1 Report
Statement of comparative novelty of the paper should be clearly stated in the introduction.
The last sentence of the INTRODUCTION does not have a verb.
Author Response
Reviewer 1
Comment 1. Statement of comparative novelty of the paper should be clearly stated in the introduction.
Response. Additional sentence about novelty of the proposed structure was added:
Moreover, the proposed structure is attractive for implementing a photonic crystal surface-emitting laser (PCSEL) [32]. Thus, the set-up proposed paves a way for engineering optical devices with both PCSEL and beam steering functionality.
Comments on the Quality of English Language
The last sentence of the INTRODUCTION does not have a verb.
Response. The last sentence has been corrected.
The metasurface from square nanobricks is separated from the photonic crystal by graphene, sapphire and ITO films.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript proposed a Tamm plasmonic system to investigate the beam steering at near-infrared frequency. The phase and amplitude of the reflected wave are adjusted by modulating the refractive index of a transparent conductive oxide layer by applying a bias voltage. It is interesting; however, some issues should be clear:
1. Intuitively, the proposed structure can excite Tamm plasmon polariton (TPP), but further theoretical supplementation is needed, and the field distribution at resonance can also help explain the physical mechanisms underlying the structure. Therefore, the authors need to supplement relevant content to fully demonstrate the excitation of TPP. For articles on TPP, please refer to Ref. 27 (in the manuscript) and [Optics Letters 44 (13), 3302-3305 (2019)].
2. In this manuscript, the simulation results are numerically obtained by FDTD. For the peers’ repetition of results, the authors should simply describe some details (for example boundary conditions, mesh setting, graphene setting) about the FDTD method.
3. In Fig. 2(c), the authors should provide more information on the phase response to voltage changes at different wavelengths.
4. Some references about Tamm states can be referred, such as [Journal of Physics D: Applied Physics 52, 015104 (2019)].
Author Response
Reviewer 2
The manuscript proposed a Tamm plasmonic system to investigate the beam steering at near-infrared frequency. The phase and amplitude of the reflected wave are adjusted by modulating the refractive index of a transparent conductive oxide layer by applying a bias voltage. It is interesting; however, some issues should be clear:
- Intuitively, the proposed structure can excite Tamm plasmon polariton (TPP), but further theoretical supplementation is needed, and the field distribution at resonance can also help explain the physical mechanisms underlying the structure. Therefore, the authors need to supplement relevant content to fully demonstrate the excitation of TPP. For articles on TPP, please refer to Ref. 27 (in the manuscript) and [Optics Letters 44 (13), 3302-3305 (2019)].
Response. We thank the Rewiever for this comment. The field distribution at the TPP wavelength has been added to figure 1d.
The reference [Optics Letters 44 (13), 3302-3305 (2019)] has been added to the introduction.
- In this manuscript, the simulation results are numerically obtained by FDTD. For the peers’ repetition of results, the authors should simply describe some details (for example boundary conditions, mesh setting, graphene setting) about the FDTD method.
Response. Additional explanations about FDTD simulation box has been added to the text:
The simulation box is shown in figure 1. The PhC structure is illuminated from the top by a plane wave with E vector along y axis as shown in figure 1. The reflectance R is calculated at the top of the simulation box. Periodic boundary conditions are applied at the lateral boundaries of the simulation box, while perfectly matched layer (PML) boundary conditions were used on the remaining top and bottom interfaces.
- In Fig. 2(c), the authors should provide more information on the phase response to voltage changes at different wavelengths.
Response. We thank the Reviewer for this comment. Indeed, the dielectric permittivity and, as a consequence, the reflection phases can be calculated for any wavelength. However, the purpose of our work is to design a device that allows deflecting a beam at a telecom wavelength of 1550 nm. In the introduction, we noted that the device was designed specifically for this wavelength:
In this paper 2D beam steering by the metasurface - photonic crystal based structure for C-band telecom wavelength is presented.
Also, for the convenience of the reader, in the caption to Figure 2, we have added explanations that in Figures 2a and 2c, the results were obtained for the wavelength of 1550 nm:
The results presented in (a) and (c) subplots were obtained for fixed wavelength at 1550 nm.
- Some references about Tamm states can be referred, such as [Journal of Physics D: Applied Physics 52, 015104 (2019)].
Response. The reference has been added to the introduction.
Author Response File: Author Response.pdf
Reviewer 3 Report
This paper entitled “two-dimensional dynamic beam steering by Tamm plasmon polariton” submitted by Rashid G Bikbaev, et.al. describes an electrically tunable beam steering using ITO electrodes and gold metasurface on an engineering substrate. The authors numerically simulated the two-dimensional phase shift from the electrically tunning and far-field steering at near-IR wavelength. The simulations are solid, while only several points need to be improved. Thus, I would recommend a major revision on this manuscript.
The major points I would like to comment on are listed below:
1. The author should comment on why they choose graphene as the electrode. What would happen if they replace graphene with gold strips? Also, the author may need to provide more explanation on the reason for the electron depletion at ITO-Al2O3 boundary is ascribe to the work function of ITO is lower than that of gold.
2. The author should at least provide justification on how they decided the material properties of ITO. Are they from references or measurement?
3. Since the authors claimed that the multilayer mirror makes high-quality resonances, the spectral sensitivity/resolution of this system should be provided. Comparison should also be provided on the performance with/without the multilayer mirrors, at least citing papers.
4. The author should comment on how does the coefficient ∆ is related to the operation resolution. Also, will resolution of the steering change when the beam is steered into a larger angle?
5. Is this system limited at 0 and +-1 diffraction order?
Minor comments:
1. Is silicon considered a phase-change-material when reference 18 is cited?
2. The author may want to remove the black lines in the phase maps in Figure 3 since they are quite disturbing.
there are some statements need to be improved. For example, from line 27 " similar effect... polariton (TPP)". The use of 'here' is unclear. Or the sentence from line 51 to 53. The way to use 'however' may not be proper.
Author Response
Reviewer 3
This paper entitled “two-dimensional dynamic beam steering by Tamm plasmon polariton” submitted by Rashid G Bikbaev, et.al. describes an electrically tunable beam steering using ITO electrodes and gold metasurface on an engineering substrate. The authors numerically simulated the two-dimensional phase shift from the electrically tuning and far-field steering at near-IR wavelength. The simulations are solid, while only several points need to be improved. Thus, I would recommend a major revision on this manuscript.
The major points I would like to comment on are listed below:
- The author should comment on why they choose graphene as the electrode. What would happen if they replace graphene with gold strips? Also, the author may need to provide more explanation on the reason for the electron depletion at ITO-Al2O3 boundary is ascribe to the work function of ITO is lower than that of gold.
Response. We thank the Reviewer for this comment. The explanations about graphene layer has been added to the text:
The choice of graphene as the lower contact is due to its high electrical conductivity and insignificant influence on the optical properties of the structure due to its small thickness. Replacing graphene with another conductive material, such as gold, will lead to a significant change in the reflection spectra of the structure.
Additionally, the reference about electron depletion at the ITO-Al2O3 boundary has been added to the text:
This is due to the fact that the work function of the ITO is lower than the work function of the gold [22].
22. Huang, Y.W.; Lee, H.W.H.; Sokhoyan, R.; Pala, R.A.; Thyagarajan, K.; Han, S.; Tsai, D.P.; Atwater, H.A. Gate-Tunable Conducting Oxide Metasurfaces. Nano Letters 2016, 16, 5319–5325. https://doi.org/10.1021/acs.nanolett.6b00555.
2. The author should at least provide justification on how they decided the material properties of ITO. Are they from references or measurement?
Response. Additional explanations about dielectric permittivity of the ITO have been added to the text:
The dielectric permittivity of ITO can be described by the Drude model εITO = ε∞ − ωp2/(ω2 + iωΓ), where ωp is the plasma frequency which is related to the carrier density N and electron effective mass m∗ as ωp2 = Ne2/(ε0m∗). Here ε0 is the dielectric permittivity of vacuum, e is the electron charge, and Γ is the damping constant. In our simulation the Drude parameters were taken from [22].
- Since the authors claimed that the multilayer mirror makes high-quality resonances, the spectral sensitivity/resolution of this system should be provided. Comparison should also be provided on the performance with/without the multilayer mirrors, at least citing papers.
Response. Corresponding explanations about Q-factor of the resonance have been added to the text:
As noted in the introduction, the Q-factor of such a resonance is greater than the Q-factor of gap plasmon resonance in conventional metal-insulator-metal structures. In our case, the Q-factor of TPP is 4 times greater than the Q-factor of the resonance presented in paper [22].
- The author should comment on how does the coefficient ∆ is related to the operation resolution. Also, will resolution of the steering change when the beam is steered into a larger angle?
Response. The Δ is not related to the operational resolution . In our case, delta is the difference between intensity in diffraction orders provided by N2 number of contacts and 2N number of contacts. In 2N-sheme increasing the angle will not lead to a change in the resolution of the device, however, at large angles, the intensity in the diffraction maximum decreases significantly.
Δ is the difference between the intensity of the diffraction maximum in the far field provided by N2- and 2N-contacts schemes.
- Is this system limited at 0 and +-1 diffraction order?
Response. Yes. In our structure only 0 and +-1 diffraction order are realized:
Thus, it is possible to form a diffraction grating of the required period and implement intensity control of 0 and ± 1 diffraction orders both in angle θ and in angle φ.
Minor comments:
- Is silicon considered a phase-change-material when reference 18 is cited?
Response. The ref. [18] was deleted. This link was not used correctly.
- The author may want to remove the black lines in the phase maps in Figure 3 since they are quite disturbing.
Response. In Figure 3, the black lines depict the boundaries of nanobricks. Perhaps the black lines are related to the low resolution of the picture. We have increased the resolution of the picture for the convenience of the readers.
Comments on the Quality of English Language
There are some statements that need to be improved. For example, from line 27 " similar effect... polariton (TPP)". The use of 'here' is unclear. Or the sentence from line 51 to 53. The way to use 'however' may not be proper.
Response. These inaccuracies have been corrected.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The authors have addressed all points in my review. I recommend accepting the paper for publication.Author Response
Reviewer 2
Comment 1. The authors have addressed all points in my review. I recommend accepting the paper for publication.
Response. We thanks the Reviewer for this comment.
Author Response File: Author Response.pdf
Reviewer 3 Report
The authors responded to my review comments in a proper way. They provide enough information for others to understand and reproduce their results, including the properties of ITO, the resolutions or adding references for electron depletion. The electro-optical tunability of metasurface is a hot topic and this work is now good for publication, to my point of view.
Author Response
Reviewer 3
The authors responded to my review comments in a proper way. They provide enough information for others to understand and reproduce their results, including the properties of ITO, the resolutions or adding references for electron depletion. The electro-optical tunability of metasurface is a hot topic and this work is now good for publication, to my point of view.
Response. We thanks the Reviewer for this comment.
Author Response File: Author Response.pdf
