Open Access
Add to BibSonomy
Abstract
Plasmon induced transparency (PIT), known as the coupling of plasmon modes in metamaterials, has attracted intensive research interests in photonic applications. In this work, a PIT-like transparency is realized via the strong coupling of plasmonic dipole and epsilon-near-zero (ENZ) mode. Two types of metasurfaces, namely the gold nanoantenna and dolmen-like metasurface, are designed with an integrated ENZ material aluminum doped zinc oxide (AZO) film. Simulations with the finite element method (FEM) demonstrate that single and double transparent windows are achieved respectively. The adjustments of the peak position and transmittance of transparent windows via the structure parameters and the AZO film thickness are further investigated. This work provides an alternative coupling scheme of realizing PIT-like transparency with simple metasurface design, and offers great potential for future metamaterial applications.
© 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
1. Introduction
In the past two decades, plenty of researches on the electromagnetically induced transparency (EIT) effect have emerged due to its significant benefits for optical devices [1–5]. Especially, the plasmon induced transparency (PIT), which is an analogue of EIT effect, has been widely applied in optical switches [6], optical sensors [7], optical filters [8], and nonlinear optical devices [9,10], owing to the intrinsic flexibility of structure design and ease of implementation in metamaterials [11–16]. Generally, PIT is realized via either the frequency mismatch of bright-bright plasmon mode coupling or the destructive interference of bright-dark plasmon mode coupling [17–20]. It is worth noting that the key to PIT is forming an extremely narrow transparency band via near-field interaction between multiple resonators. Here in this work, the motivation is to realize a PIT-like transparency through the spectral splitting mechanism induced by the strong coupling between the plasmon modes and other enhancement modes, which will be of great significance.
Recently, epsilon-near-zero (ENZ) materials with real part of permittivity vanishing at a specific wavelength exhibit the features of prominent field localization and enhancement, large nonlinear coefficient and ultrafast response time [21–27]. Transparent conducting oxides such as aluminum doped zinc oxide (AZO) are natural ENZ materials and able to confine the electric field into a deep subwavelength scale. Specifically, for an ENZ film with thickness much smaller than the skin depth, an ENZ mode can be supported with localized electric field, leading to the remarkable enhancement of the light-matter interaction [28,29]. It has been proved that the strong coupling between the plasmon resonance mode and ENZ mode will be induced when a thin ENZ film is integrated with the metasurface with adjacent resonance frequency, leading to a huge field enhancement and resonant splitting into two polariton branches on the spectrum [30–35]. ENZ film-incorporated metasurfaces have been designed to trigger the strong coupling effect and shown striking performance in nonlinear optical applications [36–41].
Herein, we introduce two types of metasurfaces incorporated with the AZO film as the ENZ layer to produce PIT-like transparency via the strong coupling of plasmonic dipole and ENZ mode. The gold nanoantenna and dolmen-like metasurfaces on the AZO layer are designed respectively. Simulations with finite element method (FEM) are performed and demonstrate that single and double transparent windows are realized correspondingly. The dependences of the PIT-like transparency properties on structure parameters and AZO film thickness are also investigated. This study provides an alternative coupling scheme to realize PIT-like transparency with simple metasurface design, and predicts tremendous potentials in future metamaterial applications.
2. Model and principle
In order to realize the strong coupling of the plasmonic dipole and ENZ modes, an AZO thin film is designed to insert between the plasmonic metasurface and substrate ($SiO_{2}$) as shown in Fig. 1(a) and 1(b). The AZO has been reported to exhibit excellent ENZ response in the near-infrared region [23]. In Fig. 1(a), the nanoantenna-AZO system is composed of gold nanoantenna array with a period of 850 nm and a thickness of 80 nm. The length and width of the unit cell are $l$ and $w$ respectively, and $l$ is set as a variant while $w$ is 180 nm during simulations. Figure 1(b) illustrates the dolmen-AZO system, where the unit cell is periodically arranged two-dimensionally with a period of $P_{x}=P_{y}$ = 600 nm. The dolmen-like metasurface consists of a single strip and two parallel legs. The dimension of the single strip is 320 nm${\times }$100 nm ($l_{1}{\times }w_{1}$), while the dimension for each of the two parallel legs is $l_{2}{\times }w_{2}$, in which the width $w_{2}$ is 70 nm and the length $l_{2}$ is set as a variant to study the dependence of structure parameter on transmission property. The gap between the two legs is $g$ = 50 nm.
Fig. 1. Schematic diagram of the gold nanoantenna metasurface (a) and gold dolmen-like metasurface (b) integrating with AZO film respectively. The insets show the unit cells of designed structures. (c) Real and imaginary parts of the permittivity of the AZO film.
According to the Drude model, the complex permittivity of the AZO film can be described as [42]:
where, $\varepsilon _{\infty }=3.8$ is the high-frequency permittivity, $\omega$ is the angular frequency, $\omega _{p}=2.37{\times }10^{15}\;rad/s$ is the plasma frequency, and $\gamma =6.8{\times }10^{13}\;rad/s$ is the Drude damping rate. The real part of $\varepsilon$ reaches zero at around 1550 nm $(\lambda _{ENZ})$ as shown in Fig. 1(c). Due to this ENZ behavior, the AZO film can support an ENZ mode when the film thickness is on the order of $(\lambda _{ENZ}/50)$ or less [28]. Thus, the thickness of AZO film $(h_{ENZ})$ is set as 30 nm. The permittivity of gold is also described by the Drude model [43], with $\varepsilon _{\infty }=1$, $\omega _{p}=1.367{\times }10^{16}\;rad/s$ and $\gamma =4.084{\times }10^{13}\;rad/s$.Numerical simulations are performed with the commercial software COMSOL Multiphysics based on the finite element method (FEM) [44,45]. In our simulations, the infinite array is set as the periodic boundary condition and the perfect matching layer is employed in the $z$ direction. The light is normally incident to the metasurface with the polarization along the $x$ direction. Owing to the presence of the surface plasmon structure, the incident light could be effectively localized in near field and permeate into the AZO film, thus breaking the incident angle limit and allowing for efficient excitation of the ENZ mode to realize strong coupling even for normal incidence [34].
3. Results and discussions
3.1 Single transparent window based on the nanoantenna-AZO system
Firstly, the transmittance spectra of the gold nanoantenna metasurface with the AZO film are calculated. In order to realize the coupling between the ENZ mode and the plasmonic dipole mode, we have designed the structure parameter of the nanoantenna, and obtained the resonant wavelength ranging from 1334 nm to 1683 nm for the bare nanoantenna to ensure good spectral overlapping with the ENZ region. In Fig. 2(a), under the excitation of incident light, the transmittance spectrum of the nanoantenna-AZO system exhibits a splitting into two asymmetric transmission dips and generates one transparent window, leading to the PIT-like transparency. The upper transmission dip (with shorter wavelength) originates from the dipole plasmon resonance excited by the nanoantenna, according to the inset of Fig. 2(a) as well as the transmittance spectra of the bare gold nanoantenna metasurface in Supplement 1, Figure S1. With the AZO layer composited under the nanoantenna array, the PIT-like transparency is realized due to the strong coupling between the plasmon mode of nanoantenna and the ENZ mode of AZO film. Besides, this PIT-like transparency can be tuned by the structure parameters of gold nanoantenna. With the length $l$ increasing, the positions of the two transmission dips and the transparent window are slightly redshifted, while the transparent window is basically centered at around the ENZ wavelength $(\lambda _{ENZ})$, denoting that the AZO film can support an ENZ mode.
Fig. 2. (a) Transmittance spectra of the gold nanoantenna metasurface with AZO film for different length of the nanoantenna $l$. The inset shows the transmittance spectra of bare nanoantennas with $l$ = 400 nm. From left to right, two transmission dips are named as the upper dip and the lower dip respectively. (b) Influence of the length $l$ on the spectral separation of the transmission dips (blue line) and the peak transmittance of the transparent window (red line). (c) The evolution of the transmission spectra of the nanoantenna-AZO system with varying nanoantenna length $l$. The curves with blue and black circles represent the transmission dip of the coupled system and bare nanoantenna, respectively. The pink dashed line indicates the ENZ wavelength.
It is noteworthy that the peak transmittance of the transparent window decreases sharply with the redshift of its position, from $91\%$ to $58\%$, as shown in Fig. 2(b). Since the shifts of the upper transmission dip wavelength indicates the change of the coupling strength, the spectral separation of splitting is positively correlated to the coupling strength [46]. Additionally, the separation of splitting decreases with the increase of nanoantenna length. Figure 2(c) shows the evolution of the transmission resonant wavelength of the nanoantenna-AZO system with varying nanoantenna length $l$. As the length $l$ varies, the resonance of the coupled system exhibits an clearly anti-crossing behavior, a typical feature of the strong coupling effect that is similar with Ref [32]. The coupling strength between the nanoantenna layer and the AZO layer gradually decreases with the increase of the nanoantenna length, since the increasing $l$ leads to the redshift of the nanoantenna plasmon resonance. In the following discussions, the length of the nanoantenna is selected as $l$ = 400 nm to ensure the strong enough coupling as well as a high transmittance of $86\%$.
To further investigate the physical mechanism of the PIT-like transparency, the |E| field distribution in the nanoantenna-AZO system is calculated. In Fig. 3(a), the |E| field for the upper transmission dip at 1315 nm is primarily localized in the nanoantenna, and leaks to the AZO film and the substrate due to weak coupling of the dipole plasmon resonance mode. The |E| field for the transmission peak at 1500 nm is localized in the AZO film with great enhancement and ends at the interface of AZO film and substrate as shown in Fig. 3(b), verifying the excitation of the ENZ mode [28]. The |E| field distribution for the lower transmission dip at 1825 nm exhibits a leakage mode at the AZO-substrate interface, since 1825 nm is far away from the ENZ region and thus the ENZ mode is weak [47]. The simulated results demonstrate that the plasmon resonance mode and the ENZ mode play dominant roles in the transmission dip and transparent window, respectively. In addition, the unchanged position of transparent window is the result of the strong interaction between the ENZ mode of AZO film and the plasmon mode of nanoantenna [38,47]. Furthermore, it is found that the lower transmission dip becomes unconspicuous with the increase of AZO film thickness, as is illustrated in Supplement 1, Figure S2. Especially, the |E| filed distribution of the transmission peak for the AZO film thickness of 150 nm is illustrated in Fig. 3(d). Compared with Fig. 3(b), the electric field for $h_{AZO}$ = 150 nm is basically distributed at the edge of the nanoantenna, which indicates that the thicker AZO film cannot support the ENZ mode anymore, leaving a single plasmon resonance mode [48]. The simulated |E| field distributions for the different thickness of AZO film are shown in Supplement 1, Figure S3.
Fig. 3. Simulated |E| field distribution in the gold nanoantenna-AZO system with $l$ = 400 nm for the upper transmission dip at 1315 nm (a), the transmission peak at 1500 nm (b) and the lower transmission dip at 1825 nm (c). (d) Simulated |E| field distribution of the transmission peak at 1500 nm for the thickness of AZO film $h_{AZO}$ = 150 nm.
3.2 Double transparent windows based on the dolmen-AZO system
In the above subsection, simulation results have demonstrated that the PIT-like transparency can be realized using a nanoantenna-AZO system. Herein, we turn our focus to the dolmen-AZO system to obtain double transparent windows.
Figure 4(a) illustrates the transmittance spectra of the gold dolmen-AZO system for different $l_{2}$ values. For the bare gold dolmen-like metasurface, one transparent window is noticed due to the typical bright-dark plasmon resonance modes coupling effect of PIT [11] as shown in the inset. The corresponding |E| field distribution is shown in Supplement 1, Figure S4. With the AZO layer underneath the dolmen-like metasurface, the incident light field is confined in the AZO film and excites the ENZ mode. Consequently, strong coupling between these two modes is generated and induces the spectral splitting. The first transparent window (left) originates from the typical PIT effect, and the second window (right) is dominated by the PIT-like transparency. With the increase of $l_{2}$, the peak transmittance of the first transparent window remains at high level of about $94\%$ due to the PIT effect, which is similar to the that of the bare gold dolmen shown in Supplement 1, Figure S5. On the other hand, the peak transmittance of the second transparent window decreases from $93\%$ to $80\%$ owing to the change of coupling strength, while still remains in the ENZ region.
Fig. 4. (a) Transmittance spectra for the gold dolmen-AZO system for different $l_{2}$. The inset is the transmittance spectra of the dolmen-like metasurface with $l_{2}$ = 110 nm. From left to right, three transmission dips are named as the upper dip, the middle dip and the lower dip respectively. (b) Simulated |E| field distribution in the $x-z$ plane of the first transparent window at 1108 nm, and (c) the second transparent window at 1493 nm, also for the case of $l_{2}$ = 110 nm. The inset in (b) is the corresponding |E| field distribution in the $x-y$ plane.
Taken the trade-off between the position and the peak transmittance of the transparent windows into account, $l_{2}$ = 110 nm is chosen for further calculations of the |E| field distribution to study the mechanism of the double transparent windows. In this case, the first transparent window is centered at 1108 nm with a peak transmittance of $93\%$, and the second transparent window is centered at 1493 nm with a peak transmittance of $91\%$. Figure 4(b) denotes that the |E| field distribution of the first transparent window is primarily distributed in the gap between the two parallel legs of the gold dolmen-like structure, similar to case in the bare dolmen-like metasurface (see Supplement 1, Figure S4(c)). This further proves that the first transparent window is induced by the PIT effect. In Fig. 4(c), the |E| field of the second transparent window is localized in the AZO layer, and is significantly greater than that at the surface of the dolmen-like structure, indicating that it is originated from the coupling between the plasmon resonance mode and the ENZ mode. In addition, the transmittance spectra for different AZO film thickness are also investigated and shown in Supplement 1, Figure S6. For thick AZO film that could not support the ENZ mode, the second transparent window disappears inevitably, and the single transparent window survives.
4. Conclusion
In summary, we have designed two metasurfaces integrating with an AZO film, which are the gold nanoantenna-AZO system and the gold dolmen-AZO system, respectively. Simulations have demonstrated that the PIT-like transparency can be realized in the nanoantenna-AZO system via the coupling of plasmonic dipole and ENZ mode. Meanwhile, the dolmen-AZO system produces double transparent windows due to both the PIT and the PIT-like transparency. The peak position and transmittance of the transparent windows can be adjusted by either the structure parameters or the AZO film thickness. This work has provided a route of realizing PIT-like transparency without complicated structure design, and may be of great help for potential applications in metamaterial devices based on spectral transparency.
Funding
National Natural Science Foundation of China (11874328, 12174351); Natural Science Foundation of Henan Province (212300410411); Natural Science Foundation of Henan Educational Committee (21A140026).
Disclosures
The authors declare no conflicts of interest.
Data availability
Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.
Supplemental document
See Supplement 1 for supporting content.
References
1. L. V. Hau, S. E. Harris, Z. Dutton, and C. H. Behroozi, “Light speed reduction to 17 metres per second in an ultracold atomic gas,” Nature 397(6720), 594–598 (1999). [CrossRef]
2. F. Zhang, Q. Zhao, J. Zhou, and S. Wang, “Polarization and incidence insensitive dielectric electromagnetically induced transparency metamaterial,” Opt. Express 21(17), 19675–19680 (2013). [CrossRef]
3. Y. Deng, G. Cao, Y. Wu, X. Zhou, and W. Liao, “Theoretical description of dynamic transmission characteristics in mdm waveguide aperture-side-coupled with ring cavity,” Plasmonics 10(6), 1537–1543 (2015). [CrossRef]
4. C. Wang, X. Jiang, G. Zhao, M. Zhang, C. W. Hsu, B. Peng, A. D. Stone, L. Jiang, and L. Yang, “Electromagnetically induced transparency at a chiral exceptional point,” Nat. Phys. 16(3), 334–340 (2020). [CrossRef]
5. G. Cao, H. Li, Y. Deng, S. Zhan, Z. He, and B. Li, “Systematic theoretical analysis of selective-mode plasmonic filter based on aperture-side-coupled slot cavity,” Plasmonics 9(5), 1163–1169 (2014). [CrossRef]
6. Z. Liu, X. Zhang, Z. Zhang, E. Gao, F. Zhou, H. Li, and X. Luo, “Simultaneous switching at multiple frequencies and triple plasmon-induced transparency in multilayer patterned graphene-based terahertz metamaterial,” New J. Phys. 22(8), 083006 (2020). [CrossRef]
7. A. Alipour, A. Farmani, and A. Mir, “High sensitivity and tunable nanoscale sensor based on plasmon-induced transparency in plasmonic metasurface,” IEEE Sens. J. 18(17), 7047–7054 (2018). [CrossRef]
8. Z. Liu, E. Gao, Z. Zhang, H. Li, H. Xu, X. Zhang, X. Luo, and F. Zhou, “Dual-mode on-to-off modulation of plasmon-induced transparency and coupling effect in patterned graphene-based terahertz metasurface,” Nanoscale Res. Lett. 15(1), 1 (2020). [CrossRef]
9. Z. Bai and G. Huang, “Plasmon dromions in a metamaterial via plasmon-induced transparency,” Phys. Rev. A 93(1), 013818 (2016). [CrossRef]
10. T. Nurmohammadi, K. Abbasian, and R. Yadipour, “Ultra-fast all-optical plasmon induced transparency in a metal–insulator–metal waveguide containing two kerr nonlinear ring resonators,” J. Opt. 20(5), 055504 (2018). [CrossRef]
11. S. Zhang, D. A. Genov, Y. Wang, M. Liu, and X. Zhang, “Plasmon-induced transparency in metamaterials,” Phys. Rev. Lett. 101(4), 047401 (2008). [CrossRef]
12. Y. Deng, G. Cao, H. Yang, X. Zhou, and Y. Wu, “Dynamic control of double plasmon-induced transparencies in aperture-coupled waveguide-cavity system,” Plasmonics 13(1), 345–352 (2018). [CrossRef]
13. G. Lai, R. Liang, Y. Zhang, Z. Bian, L. Yi, G. Zhan, and R. Zhao, “Double plasmonic nanodisks design for electromagnetically induced transparency and slow light,” Opt. Express 23(5), 6554–6561 (2015). [CrossRef]
14. X. Zhang, Z. Liu, Z. Zhang, E. Gao, X. Luo, F. Zhou, H. Li, and Z. Yi, “Polarization-sensitive triple plasmon-induced transparency with synchronous and asynchronous switching based on monolayer graphene metamaterials,” Opt. Express 28(24), 36771–36783 (2020). [CrossRef]
15. X. He, F. Liu, F. Lin, and W. Shi, “Graphene patterns supported terahertz tunable plasmon induced transparency,” Opt. Express 26(8), 9931–9944 (2018). [CrossRef]
16. T. Wang, M. Cao, Y. Zhang, and H. Zhang, “Tunable polarization-nonsensitive electromagnetically induced transparency in dirac semimetal metamaterial at terahertz frequencies,” Opt. Mater. Express 9(4), 1562–1576 (2019). [CrossRef]
17. X.-R. Jin, J. Park, H. Zheng, S. Lee, Y. Lee, J. Y. Rhee, K. W. Kim, H. S. Cheong, and W. H. Jang, “Highly-dispersive transparency at optical frequencies in planar metamaterials based on two-bright-mode coupling,” Opt. Express 19(22), 21652–21657 (2011). [CrossRef]
18. S.-X. Xia, X. Zhai, L.-L. Wang, and S.-C. Wen, “Plasmonically induced transparency in double-layered graphene nanoribbons,” Photonics Res. 6(7), 692–702 (2018). [CrossRef]
19. X. Zhao, C. Yuan, L. Zhu, and J. Yao, “Graphene-based tunable terahertz plasmon-induced transparency metamaterial,” Nanoscale 8(33), 15273–15280 (2016). [CrossRef]
20. R. Yahiaoui, J. A. Burrow, S. M. Mekonen, A. Sarangan, J. Mathews, I. Agha, and T. A. Searles, “Electromagnetically induced transparency control in terahertz metasurfaces based on bright-bright mode coupling,” Phys. Rev. B 97(15), 155403 (2018). [CrossRef]
21. M. Z. Alam, I. De Leon, and R. W. Boyd, “Large optical nonlinearity of indium tin oxide in its epsilon-near-zero region,” Science 352(6287), 795–797 (2016). [CrossRef]
22. L. Caspani, R. P. M. Kaipurath, M. Clerici, M. Ferrera, T. Roger, J. Kim, N. Kinsey, M. Pietrzyk, A. Di Falco, V. M. Shalaev, A. Boltasseva, and D. Faccio, “Enhanced nonlinear refractive index in ε-near-zero materials,” Phys. Rev. Lett. 116(23), 233901 (2016). [CrossRef]
23. O. Reshef, I. De Leon, M. Z. Alam, and R. W. Boyd, “Nonlinear optical effects in epsilon-near-zero media,” Nat. Rev. Mater. 4(8), 535–551 (2019). [CrossRef]
24. A. D. Neira, N. Olivier, M. E. Nasir, W. Dickson, G. A. Wurtz, and A. V. Zayats, “Eliminating material constraints for nonlinearity with plasmonic metamaterials,” Nat. Commun. 6(1), 7757 (2015). [CrossRef]
25. X. Niu, X. Hu, S. Chu, and Q. Gong, “Epsilon-near-zero photonics: A new platform for integrated devices,” Adv. Opt. Mater. 6(10), 1701292 (2018). [CrossRef]
26. A. Capretti, Y. Wang, N. Engheta, and L. D. Negro, “Enhanced third-harmonic generation in si-compatible epsilon-near-zero indium tin oxide nanolayers,” Opt. Lett. 40(7), 1500–1503 (2015). [CrossRef]
27. A. Baev, P. N. Prasad, M. Z. Alam, and R. W. Boyd, “Dynamically controlling local field enhancement at an epsilon-near-zero/dielectric interface via nonlinearities of an epsilon-near-zero medium,” Nanophotonics 9(16), 4831–4837 (2020). [CrossRef]
28. S. Campione, I. Brener, and F. Marquier, “Theory of epsilon-near-zero modes in ultrathin films,” Phys. Rev. B 91(12), 121408 (2015). [CrossRef]
29. S. Vassant, J.-P. Hugonin, F. Marquier, and J.-J. Greffet, “Berreman mode and epsilon near zero mode,” Opt. Express 20(21), 23971–23977 (2012). [CrossRef]
30. Y. C. Jun, J. Reno, T. Ribaudo, E. Shaner, J.-J. Greffet, S. Vassant, F. Marquier, M. Sinclair, and I. Brener, “Epsilon-near-zero strong coupling in metamaterial-semiconductor hybrid structures,” Nano Lett. 13(11), 5391–5396 (2013). [CrossRef]
31. S. Campione, S. Liu, A. Benz, J. F. Klem, M. B. Sinclair, and I. Brener, “Epsilon-near-zero modes for tailored light-matter interaction,” Phys. Rev. Appl. 4(4), 044011 (2015). [CrossRef]
32. S. Campione, J. R. Wendt, G. A. Keeler, and T. S. Luk, “Near-infrared strong coupling between metamaterials and epsilon-near-zero modes in degenerately doped semiconductor nanolayers,” ACS Photonics 3(2), 293–297 (2016). [CrossRef]
33. K. Manukyan, M. Z. Alam, C. Liu, K. Pang, H. Song, Z. Zhao, M. Tur, R. W. Boyd, and A. E. Willner, “Dependence of the coupling properties between a plasmonic antenna array and a sub-wavelength epsilon-near-zero film on structural and material parameters,” Appl. Phys. Lett. 118(24), 241102 (2021). [CrossRef]
34. M. Z. Alam, S. A. Schulz, J. Upham, I. De Leon, and R. W. Boyd, “Large optical nonlinearity of nanoantennas coupled to an epsilon-near-zero material,” Nat. Photonics 12(2), 79–83 (2018). [CrossRef]
35. C. Liu, M. Z. Alam, K. Pang, K. Manukyan, O. Reshef, Y. Zhou, S. Choudhary, J. Patrow, A. Pennathurs, H. Song, Z. Zhao, R. Zhang, F. Alishahi, A. Fallahpour, Y. Cao, A. Almaiman, J. M. Dawlaty, M. Tur, R. W. Boyd, and A. E. Willner, “Photon acceleration using a time-varying epsilon-near-zero metasurface,” ACS Photonics 8(3), 716–720 (2021). [CrossRef]
36. X. Niu, X. Hu, Q. Sun, C. Lu, Y. Yang, H. Yang, and Q. Gong, “Polarization-selected nonlinearity transition in gold dolmens coupled to an epsilon-near-zero material,” Nanophotonics 9(16), 4839–4851 (2020). [CrossRef]
37. X. Niu, X. Hu, Y. Xu, H. Yang, and Q. Gong, “Ultrafast all-optical polarization switching based on composite metasurfaces with gratings and an epsilon-near-zero film,” Adv. Photonics Res. 2(4), 2000167 (2021). [CrossRef]
38. Z. Xie, J. Wu, H. Fu, and Q. Li, “Tunable electro- and all-optical switch based on epsilon-near-zero metasurface,” IEEE Photonics J. 12(4), 1–10 (2020). [CrossRef]
39. J. R. Hendrickson, S. Vangala, C. Dass, R. Gibson, J. Goldsmith, K. Leedy, D. E. Walker, J. W. Cleary, W. Kim, and J. Guo, “Coupling of epsilon-near-zero mode to gap plasmon mode for flat-top wideband perfect light absorption,” ACS Photonics 5(3), 776–781 (2018). [CrossRef]
40. G. Marino, P. Segovia, A. V. Krasavin, P. Ginzburg, N. Olivier, G. A. Wurtz, and A. V. Zayats, “Second-harmonic generation from hyperbolic plasmonic nanorod metamaterial slab,” Laser Photonics Rev. 12(2), 1700189 (2018). [CrossRef]
41. J. Deng, Y. Tang, S. Chen, K. Li, A. V. Zayats, and G. Li, “Giant enhancement of second-order nonlinearity of epsilon-near- zero medium by a plasmonic metasurface,” Nano Lett. 20(7), 5421–5427 (2020). [CrossRef]
42. G. V. Naik, V. M. Shalaev, and A. Boltasseva, “Alternative plasmonic materials: Beyond gold and silver,” Adv. Mater. 25(24), 3264–3294 (2013). [CrossRef]
43. M. A. Ordal, L. L. Long, R. J. Bell, S. E. Bell, R. R. Bell, R. W. Alexander, and C. A. Ward, “Optical properties of the metals al, co, cu, au, fe, pb, ni, pd, pt, ag, ti, and w in the infrared and far infrared,” Appl. Opt. 22(7), 1099–1119 (1983). [CrossRef]
44. X. Wu, Y. Zheng, Y. Luo, J. Zhang, Z. Yi, X. Wu, S. Cheng, W. Yang, Y. Yu, and P. Wu, “A four-band and polarization-independent bds-based tunable absorber with high refractive index sensitivity,” Phys. Chem. Chem. Phys. 23(47), 26864–26873 (2021). [CrossRef]
45. F. Zhou, F. Qin, Z. Yi, W. Yao, Z. Liu, X. Wu, and P. Wu, “Ultra-wideband and wide-angle perfect solar energy absorber based on ti nanorings surface plasmon resonance,” Phys. Chem. Chem. Phys. 23(31), 17041–17048 (2021). [CrossRef]
46. C. Ciuti, G. Bastard, and I. Carusotto, “Quantum vacuum properties of the intersubband cavity polariton field,” Phys. Rev. B 72(11), 115303 (2005). [CrossRef]
47. S. A. Schulz, A. A. Tahir, M. Z. Alam, J. Upham, I. De Leon, and R. W. Boyd, “Optical response of dipole antennas on an epsilon-near-zero substrate,” Phys. Rev. A 93(6), 063846 (2016). [CrossRef]
48. J. Kim, A. Dutta, G. V. Naik, A. J. Giles, F. J. Bezares, C. T. Ellis, J. G. Tischler, A. M. Mahmoud, H. Caglayan, O. J. Glembocki, A. V. Kildishev, J. D. Caldwell, A. Boltasseva, and N. Engheta, “Role of epsilon-near-zero substrates in the optical response of plasmonic antennas,” Optica 3(3), 339–346 (2016). [CrossRef]
