High Electric Field Enhancement Induced by Modal Coupling for a Plasmonic Dimer Array on a Metallic Film

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript investigates the electric field characteristics of a coupling structure with a dimer array that excites a metal film and surface lattice resonance (SLR). Common computational methods, including FDTD, were employed, and the results obtained are considered reliable by the reviewers. However, the authors should address the following comments and revise the manuscript to satisfy the concerns of many readers:

 

1. As shown in Figure 3(a), there is a sudden change in the excitation wavelength around a cavity length of 250. However, the authors treat the modes excited at these cavity lengths as identical. Reviewers find this unnatural, and the authors should clarify the optical behavior at these cavity lengths.

 

2. The manuscript claims that, in this composite structure, coupling between SLR and SPP modes can result in approximately 1.7 times amplification of the electric field compared to SLR alone. However, typically, such couplings (or the generation of Fabry-Perot) are expected to lead to a significant increase in electric field intensity. Is the electric field amplification described in this manuscript typical?

 

3. In structures of this kind, the generation of a strong magnetic field outside the structure has been reported. Have the authors conducted calculations regarding the magnetic field?

 

 

4. Please check the grammar throughout the manuscript. For example, there are several instances where "dimmer" should be corrected.

Comments on the Quality of English Language

Please check the grammar throughout the manuscript. For example, there are several instances where "dimmer" should be corrected.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Please see the full review attached.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Ensure consistency in the use of terminology and grammar throughout the paper. This includes the consistent use of tense, voice (active or passive), and technical terms. Standardizing these elements will enhance the paper's professionalism and make it easier to follow.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript investigates a hybrid structure of a hemispheric dimer array and a gold film, revealing resonant mode coupling of surface lattice resonance (SLR) and surface plasmon polariton (SPP). Anti-crossing in reflection spectra indicates Rabi splitting. Despite not reaching strong coupling, the hybrid structure exhibits improved quality factor (Q~350) and enhanced electric field in the dimer gap, surpassing single dimer or dimer array structures. Electric field enhancement exceeds 500, making the hybrid structure versatile for biosensing, nanolasing, and nonlinear optical devices. The study explores coupling effects and Fabry-Perot cavities in metallic nanoparticle arrays and films, emphasizing the importance of field enhancement for various plasmonic applications.

In my assessment, the simulation findings of this work contribute to high-Q plasmonic surface lattice resonances, a topic of interest. Hence, I support the publication of this work, on the condition that certain concerns are addressed. Please find my suggestions and comments for the authors below.

 

“Further ways to enhance the field strength between nanodimers are coupling effects or the formation of Fabry-Perot (FP) thin film cavities, such as coupling between surface 46 lattice resonance (SLR) and surface plasmon polariton (SPP), and the formation of FP.” Correct. However, some recent advancements in plasmonic field enhancements using high-Q resonances are missing. For example, (1) strong field enhancement in plasmonic high-Q metasurfaces [kivshar et al. Nano Lett. 2020, 20, 9, 6351–6356]; (2) the direction of plasmonic BIC for weak spatially coherent light. These two avenues represent new technologies in the realm of plasmonic field enhancement.

 

The assertion made by the authors that "When the Rayleigh anomaly (RA) is on the low energy side of the localized surface plasmon resonance (LSPR), the RA can couple to the LSPR forming a SLR" is inaccurate. The wavelength of LSPR can be either longer or shorter than that of SLRs. An example illustrating this is when λ_LSPR > λ_SLR, as demonstrated in the study titled "Coupling bright and dark plasmonic lattice resonances" [Physical Review X 1.2 (2011): 021019]. Therefore, the stated claim is problematic and needs revision to accurately reflect the variability in wavelengths between RA and LSPR.

 

Quote: "Although the interaction of the two resonant modes does not enter the region of strong coupling, an increase of Q factor (~350) for the hybrid modes is obtained compared to that of SLR only in Fig. 2." How does the quality factor of the hybrid modes compare to that of the SLR only?

 

 

What is the significance of the anti-crossing observed in the reflection spectra?

Comments on the Quality of English Language

readable

Author Response

Please see the attachment

Author Response File: Author Response.pdf