Fengyu Zhou, Fang Liu^{*}, Long Xiao, Kaiyu Cui, Xue Feng, Wei Zhang, Yidong Huang 
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NanoMicro Lett. (2017) 9: 9 

Published Online: 27 September 2016 (Article) 

DOI: 10.1007/s4082001601108 

*Corresponding author. Email: liu_fang@tsinghua.edu.cn 
Abstract
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1 Introduction
Surface plasmon polariton (SPP) has been an attractive and extensively studied topic in the scientific community for its various unique features. It has shown promising applications in many fields such as highly integrated optical circuits, high sensitive biological sensing, enhancing lightmatter interaction, and so on [16].
Although SPP modes can be designed by varying the metal structure, the frequency range and propagation loss still depends on the metal material. For example, on the semiinfinite metal surface, SPP mode cannot exist within the frequency range of [1, 7], where ωp is the plasma frequency of metal, ω∞ is the background permittivity of metal, and ε1 is the permittivity of semiinfinite dielectric upon the metal. Dielectrics with large permittivity ε1, such as Si or GaAs which are well used in some functional SPP devices [89], would lead to the decrease of εsp and the cutoff of SPP mode. In some cases, even though SPP mode is not cutoff, the surrounding with large permittivity would result in extremely large propagation loss at certain optical frequency range.
Metamaterial at optical frequency can be regarded as a kind of manmade material with properties beyond natural materials [10]. One of its prominent properties is that the equivalent permittivities on different directions differ from each other and can be varied by designing its structure elaborately [10]. This property promises that metamaterial may serve for SPP propagating with more flexible performances than conventional metal to deal with the problems mentioned above. As we know, the study of SPP on metamaterial is mainly based on abstracted models by assuming the permittivity of the material as fixed indefinite tensors rather than functions of the specific physical structure [2], so that the conclusions are more concerned about the generality instead of pertinence.
In this paper, the surface mode existing on the surface of the metamaterial structure composed of alternate layers of metal and dielectric material is studied. The surface mode can be guided by the multilayers structure and represents some unexpected properties. The dispersion relation of the surface mode for multilayers is deduced and the corresponding characteristic parameters are computed. Later analysis indicates that this surface mode originated from the reaction of electromagnetic field and the free electrons oscillation in metal film and thus it is a kind of SPP mode.
Compared with the conventional pure metal guided SPP, the multilayerguided SPP has larger mode field distribution and much lower energy loss at the same frequency. More importantly, it is amazing that this structure has the ability to extend the SPP mode to higher frequency surrounding with a high permittivity material, where traditional metal SPP cannot exist. Both the theoretical calculation and the physical explanation are provided to interpret this counterintuitive phenomenon in this paper. Considering the multilayers as an artificial metamaterial, it is possible to manipulate the properties of SPP mode by adjusting the structure parameters such as the depth ratio for each layer to meet different actual demands.
2 Schematic Structure and Effective Medium Model
Figure 1 illustrates the diagram of metaldielectric multilayer metastructure, which consists of silver and SiO2 layers with thickness ratio dmetal:ddie = 2:1. The upper space above multilayers (z > 0) is filled with isotropic dielectric with permittivity ε1. The permittivity of SiO2 is fixed at εdie = n2 ≈ 2.4 [11] and the relative permittivity for silver is based on Drude model [12]
Figure 1 Schematic of metaldielectric multilayers metastructure. Here, the gray and brown layers stand for metal (silver) and dielectric, respectively. The multilayers occupy the halfspace (z 0). 
Where ε∞ = 5.3, ωp = 1.39 × 1016 s1, and γ = 32 THz [12]. The permittivity of silver might be somewhat different according to different models and measurement methods [13]. Nevertheless, the main conclusion of this paper would not be affected.
When the thickness of both metal and dielectric is around ten nanometers and therefore much smaller than the wavelength here, it would be reasonable to use the effective medium theory to describe this structure [14]. According to the effective medium theory, the multilayers are regarded as an anisotropic medium with permittivity εx and εz (the xaxis is along the propagation direction, while the zaxis is perpendicular to the interface). Assuming that the structure is unvarying along the yaxis, this is a twodimensional problem. By applying the electromagnetic boundary conditions to this model, the approximate value for εx and εz can be expressed as [10, 1516]:
According to Eqs. 2 and 3, the εx and εz as functions of the frequency are shown in Fig. 2. In different frequency bands, εx and εz may change their signs and the multilayers exhibit different properties. At low frequency (band 1), the multilayers can be regarded as type II hyperbolic materials [10]. As the frequency goes up, the permittivity in both directions turns negative (band 2). In band 3, the multilayers have the feature of type I hyperbolic materials [10]. If the frequency is high enough, the multilayers become anisotropic dielectric with positive permitivities in both x and z axes (band 4). Here, we mainly focus on band 1 and band 2 to analyze the surface wave of metaldielectric multilayers. The comparison between Fig. 2a, b indicates that the variation tendency of (εx, εz) is closely related to dmetal:ddie. For simplicity, we only discuss the situation of dmetal ≥ ddie, so the permittivity applied in following passages will be based on Fig. 2a.
Figure 2 Real parts of εx and εz as a function of frequency. The depth ratio dmetal:ddie is set at (a) 2:1 and (b) 1:2. According to the signs of εx and εz, the frequency can be divided into 4 bands as shown in the figure. 
3 The Dispersion Relationship
In analogy to the traditional metalSPP, it is reasonable to suppose that the surface wave of metaldielectric multilayers also results from the coupling between electromagnetic field and electronic oscillation [1, 17]. The wave is bounded to the interface of metamaterial and propagates along the interface. In the normal direction, the electromagnetic field decays exponentially so that the energy is confined near the interface and will not propagate into the material.
Similar to metalSPP, the surface waves guided by multilayers should also be TM polarized. Hy, Ex, Ez can be used to describe the electromagnetic field in the space. For z ˃ 0 , the field components are:
For z ˂ 0, we have:
In Eqs. 4 and 5, k1 = i × kz,f, k2 = i × kz,m, where kz,f and kz,m represent wave vector components that is perpendicular to the interface in two areas (z ˃ 0 and z ˂ 0), respectively. Replacing kz,f, kz,m by k1, k2 makes Eqs. 4 and 5 match the form of the evanescent field in z direction. At z = 0, the continuity of Hy requires H1 = H2 while the continuity of Ex requires
The relationship between each component of the wave vector in both areas is as follows [2, 16]:
Solving Eq. 6 to 8 gives the dispersion relation between ω and β:
With Eq. 9, the dispersion relation is obtained and shown in Fig. 3.
4 Frequency Range of SPP
Figure 3 shows the dispersion curves of the multilayer metamaterial with different background material. Even though the graph shares the similar outline with that of traditional metalSPP, the dispersion curve for multilayers also has special features that deserve some words. It is well known that traditional metalSPP has one horizontal asymptote at frequency of , which also serves as the upper bound for SPP frequency range [12]. Nevertheless, the same rule cannot be applied to SPP on multilayers (multilayerSPPs) directly, and some discussions are required.
Figure 3 Dispersion curves with different background material (in the area with z > 0). The permittivity ε1 for z > 0 is associated with different kinds of materials [1517]: (a) air, (b) CH3CH2OH, (c) TiO2 and (d) Si. 
4.1 Frequency Upper Bound
For multilayerSPPs, the horizontal asymptote appears when and only when β goes to infinity. It can be deduced from Eq. 9 that the corresponding condition is
In other words, Eq. 10 determines the position of horizontal asymptotes. It also manifests that εx must share the same sign with εz and implies that different ε1 will result in different curve types.
When ε12 is larger than limω→∞ εxεz, Eq. 10 holds only when both εx and εz are negative, which corresponds to band 2 in Fig. 2a. Therefore, the dispersion curve has only one horizontal asymptote, just like metalSPP, and the dispersion curve under such circumstance resembles metalSPP very closely (see Fig. 3c, d).
For smaller ε1, points within band 2 and band 4 may both satisfy Eq. 10. It may result in two horizontal asymptotes in the dispersion curve and make the curve a little bit different from that of metalSPP at higher frequency, which is illustrated by Fig. 3a, b.
Similar to ωsp for metal, the position of the lowest horizontal asymptote marks the upper bound for SPP (the reason will be discussed in the next section). To distinguish the upper bound of multilayerSPPs and that of metalSPP (i.e., ωsp), the upper bound frequency is denoted as ωupper. It is easy to verify that multilayerSPPs can be excited at any frequency lower than ωupper in band 2.
4.2 Frequency Lower Bound
The dispersion curve above is obtained based on the assumption that the electromagnetic field decays exponentially in z direction. Although the dispersion curve shown in Fig. 4a left is similar to that of conventional metalSPP, not all the mode with frequency below ωupper is SPP here. In order to obtain the multilayerSPPs, it is necessary to make sure that both kz,m and kz,f are imaginary. According to Fig. 4, the frequency is cut into three regions by two cutoff points, ωlower and ωupper. ωupper has been defined in Sec. 4.1 as the frequency of the lowest horizontal asymptote in the dispersion curve, while ωlower, lower than ωupper, is the frequency where both kz,m and kz,f convert from real to imaginary. This section will later prove that the realtoimaginary turning points for kz,m and kz,f are the same.
Figure 4 Each component of wave vector. Corresponding to Fig. 3d, the background material is assumed as ε1 = 13 [18]. a The components of β and k in both multilayers and the free space. b The schematic diagram of electromagnetic field in different frequency ranges. Both the left and right figures represent the bulk mode of electromagnetic field at low frequency (in region 1) and at high frequency (in region 3), respectively, where the wave vectors k and the Poynting vectors S differ in two regions due to different permittivities. The middle figure stands for the surface wave and the depth skins. 
As shown in Fig. 4a, in region 1, the real part of kz,m in multilayers exists while the imaginary part is negligible, which indicates that the electromagnetic wave can propagate into the material with little damping. Region 1 ends at the frequency ωlower and region 2 begins here. In region 2, kz,m has relatively large imaginary part and negligible real part. It means that the field is evanescent in this region. When the frequency is higher than ωupper (in region 3), the real part of kz,m emerges and the imaginary part disappears again. The right figure in Fig. 4a displays the wave vector component kz,f in the free space. Similarly, the wave can propagate into the free space in region 1 and 3, while it is bounded to the interface in region 2.
Now it is the time to prove that the realtoimaginary turning points ωlower for both kz,m and kz,f are the same. Suppose that the realtoimaginary turning points for kz,m is ωlower while that for kz,f is ωlower,2.
In multilayers (), Eq. 8 can be rewritten in the following form:
It is known that ωupper is in band 2 and the concerned turning point (ωlower,1 and ωlower,2) is below ωupper. The discussion in previous sections implies that this turning point is within band 1 (εx ˂ 0, εz ˃ 0). The multilayers can be regarded as the hyperbolic material in this band and Eq. 11 turns to be
For evanescent field in multilayers, kz,m should be imaginary (kz,m2 ˂ 0) and we obtain
Applying Eq. 9, we have
Thus, in order to have the evanescent field in multilayers, condition (Eq.13) is required. According to the definition that ωlower,1 is the realtoimaginary turning points for kz,m, ωlower,1 should correspond to the critical point of (Eq.13). In other words, ωlower,1 marks the frequency at which ε1= εz .
In the dielectrics above multilayers (z > 0), we rewrite (Eq. 7) as
Similarly, the evanescent field requires kz,f to be imaginary (kz,f 2 ˂ 0) so that
ωlower,2, the realtoimaginary turning points for kz,f, corresponds to the critical condition for (Eq. 15), i.e., ε1= εz, which is the same as the condition for ωlower,1. Hence, the lower cutoff point can be uniquely denoted as ωlower.
Now, we assert that the SPP appears only within region 2, which spans from ωlower to ωupper. The corresponding condition is
(in band 1) or
In this range, the SPP can be excited by evanescent field (by using prisms [17], electrons [1921], etc.). When the wave vector in the propagation direction is matched, the multilayerSPPs will be excited and propagate stably.
4.3 Frequency Range
Knowing the lower and upper bound of multilayerSPPs, its frequency is completely determined. Figure 5 displays the frequency range of multilayerSPPs (blue part), together with that of metalSPP (red part). The metalSPP frequency range spans from 0 to 517 THz, while the multilayerSPPs spans from 434 to 710 THz. It can be clearly observed that multilayerSPPs has higher and narrower frequency range than metal. As we know, the surface plasmon results from the oscillation of free electrons at the metal surface. Intuitively, the decrease of the number of free electrons would lead to the reduction of frequency range since the negativity of εm is correlated to the density of free electrons positively. In general cases, the metal with lower free electron density indeed displays a lower ωsp, which marks the frequency range upper bound. Here, the multilayers with less free electron density by replacing some parts of the metal with dielectric layers should lead to the decreased ωsp. However, the structure of multilayers contradicts with this intuition. The computation implies that this structure has the ability to extend the SPP to some higher frequency where even metalSPP cannot exist.
Figure 5 a Propagation length, b skin depth in multilayers, and c skin depth in free space of metalSPP and multilayersSPP. The blue and red colors are to mark the frequency range of multilayerSPPs and metalSPP, respectively. 
Inspired by this counterintuitive conclusion, we further increase the ratio of dielectric layers in the multilayers structure. Figure 6 shows the SPP frequency range as the depth ratio ddie:dmetal goes from 0.01 to 1. As we have assumed that dmetal ≥ ddie, the ratio ddie:dmetal will not be greater than 1. From the figure, it is clear that the upper bound of frequency range has been elevated to nearly 800 THz when ddie:dmetal ≈ 1, while metalSPP can only reach 500~550 THz under the same condition. This improvement works when the background material has high permittivity. In our case, we use Si (whose permittivity is around 13) to fill the area z > 0. The figure indicates that the thicker the dielectric layers in multilayers are, the higher multilayerSPPs frequency range can reach. It also contradicts with the intuition.
Figure 6 The blue area determined by ωupper and ωlower represents the frequency range of multilayersSPP. The red dashed line marks ωsp for pure metal (silver). Corresponding to the orange dashed line, the inset reveals the dispersion curve of multilayersSPP as dmetal:ddie = 0.5. 
5 Propagation Length and Skin Depth
Obtaining the wave vectors, the characteristic length of multilayerSPPs can be computed and analyzed. The propagation length and skin depth are expressed as [22, 23],
Here, Li stands for the propagation length in x direction, and δm, δf stand for the skin depths in the material (metal or multilayers) and free space, respectively. Setting ε1=13, Fig. 5 shows the above feature length of both metalSPP and multilayerSPPs. It is clear that the propagation length of multilayerSPPs is around 5 times longer than that of metalSPP at the same frequency. Thus, the propagation loss of multilayerSPPs is much lower than that of metalSPP. This is because more field of multilayerSPPs expands into the dielectric area (z ˃ 0) (Fig. 5c) and meanwhile exists in the dielectric parts of multilayers structure (z ˂ 0) (Fig. 5b). Thus, in some circumstances, using the multilayers structure to substitute original metal material would result in longer propagation length. And by adjusting the ratio of metal and dielectric in multilayers, the properties of SPP mode could be tuned.
6 Discussion
For traditional metalSPP, to fulfill the electromagnetic boundary condition, the absolute value of Re(εm) should be larger than dielectric permittivity ε1, and the electric field component Ex should not be larger than Ez. Otherwise, the SPP mode would be cutoff. We assume that Ezsmaller than Ex is a criterion for judging the existence of SPP mode, although it is not rigorous for multilayers structure.
From the perspective of effective medium, multilayers present the property of anisotropic material under certain circumstances, as shown in Sec. 2. Further, Fig. 2 indicates that multilayers could be regarded as anisotropic metal near the upper bound of its SPP frequency range (in band 2). Within band 2 of Fig. 2a, the Re(εz) is far from zero, while Re(εx) is much closer to zero, compared with the Re(εm) of pure metal.
Due to the much larger absolute value of Re(εz) than that of Re(εx), considering the continuity of electric field Ex along x and electric displacement field εi·Ez (i = 1 or z ) along z at z = 0, the electric field component Ez could be kept smaller than Ex even though the dielectric permittivity ε1 is increased a lot. Thus, the SPP could be supported by the multilayers with high ε1 according to the nonrigorous criterion mentioned above.
Since the extension of SPP frequency is due to the abnormal effective permittivity of multilayer structure along x and z direction. The effective permittivity results from the interaction of electromagnetic field with the free electrons in metal layers and the SPP mode coupling and resonant in multilayer metaldielectric structure. Therefore, the extension of SPP frequency range is ascribed to the SPP mode coupling and resonant in the multilayers with anisotropic permittivity.
By the way, the multilayerSPPs could also be excited by evanescent electromagnetic field generated by prism, grating or waveguide. The extended frequency range, lower propagation loss, and tunable properties by changing the metaldielectric ratio might be useful for biosensor, integrated circuits, active SPP devices.
7 Conclusions
The SPP guided by metal/dielectric multilayers metamaterial was studied theoretically. Regarding the metamaterial as an anisotropic material by the effective medium theory, the dispersion relation of the SPP was derived. It is revealed that SPP can be supported by the metamaterial at the frequency where conventional metalSPP cannot exist when the permittivity of dielectric on metal is high. Besides the difference of high frequency cutoff point compared with metalSPP, it was found that there exists a low cutoff frequency, below which SPP could not be supported by the metamaterial. The calculation results also revealed that the multilayerSPPs has larger propagation length and skin depth compared with metalSPP. Therefore, at some specific frequency, multilayers could be more favorable than metal in transmitting signals.
These amazing properties provide the possibility to make use of SPP mode for some potential applications, which are impossible for metalSPP, such as optical interconnection and active SPP devices, where Si and active IIIV material (GaAs) with high permittivity might result in the cutoff of SPP mode or extremely large loss at certain frequency. Besides, the characteristics of the multilayerSPPs are easy to be manipulated by adjusting the structure parameters and the active materials can also be introduced into the metamaterial, which might bring more interesting features to future devices.
Acknowledgements
This work was supported by the National Basic Research Programs of China (973 Program) under Contracts No. 2013CBA01704, and the National Natural Science Foundation of China (NSFC61575104).
References
[1] S.A. Maier, H.A. Atwater, Plasmonics: Localization and guiding of electromagnetic energy in metal/dielectric structures. J. Appl. Phys. 98, 011101 (2005). doi:10.1063/1.1951057 [2] W. Yan, L.F. Shen, L.X. Ran, J.A. Kong, Surface modes at the interfaces between isotropic media and indefinite media. J. Opt. Soc. Am. A 24(2), 530535 (2007). doi:10.1364/JOSAA.24.000530 [3] D. Zhang, Q. Zhang, Y. Lu, Y. Yao, S. Li, J. Jiang, G.L. Liu, Q. Liu, Peptide functionalized nanoplasmonic sensor for explosive detection. NanoMicro Lett. 8(1), 3643 (2016). doi:10.1007/s408200150059z [4] S. Zeng, K.V. Sreekanth, J. Shang, T. Yu, C. Chen et al., Graphene–gold metasurface architectures for ultrasensitive plasmonic biosensing. Adv. Mater. 27(40), 61636169 (2015). doi:10.1002/adma.201501754 [5] O. Takayama, D. Artigas, L. Torner, Lossless directional guiding of light in dielectric nanosheets using Dyakonov surface waves. Nat. Nanotechnol. 9(6), 419424 (2014). doi:10.1038/nnano.2014.90 [6] M. Sun, T. Sun, Y. Liu, L. Zhu, F. Liu, Y. Huang, C.C. Hasnain, Integrated Plasmonic Refractive Index Sensor Based on Grating/Metal Film Resonant Structure, Proc. SPIE 9757, High Contrast Metastructures V, (March 15, 2016): SPIE, 97570Q (2016). doi:10.1117/12.2218558 [7] H.T.M. Baltar, K. DrozdowiczTomsia, E.M. Goldys, Plasmonics Principles and Applications (K. Y. Kim, Eds), InTech, Rijeka, pp. 136155 (2012). [8] J.T. Kim, J.J. Ju, S. Park, M. Kim, S.K. Park, M.H. Lee, Chiptochip optical interconnect using gold longrange surface plasmon polariton waveguides. Opt. Express 16(17), 1313313138 (2008). doi:10.1364/OE.16.013133 [9] Y. Li, H. Zhang, T. Mei, N. Zhu, D.H. Zhang, J. Teng, Effect of dielectric cladding on active plasmonic device based on InGaAsP multiple quantum wells. Opt. Express 22(21), 2559925607 (2014). doi:10.1364/OE.22.025599 [10] P. Shekhar, J. Atkinson, Z. Jacob, Hyperbolic metamaterials: fundamentals and applications. Nano Convergence 1(1), 14 (2014). doi:10.1186/s4058001400146 [11] G. Ghosh, Dispersionequation coefficients for the refractive index and birefringence of calcite and quartz crystals. Opt. Commun. 163(13), 95102 (1999). doi:10.1016/S00304018(99)000917 [12] S.A. Maier, Plasmonics: Fundamentals and Applications, Springer, Berlin, pp 534 (2007). [13] H.U. Yang, J. D'Archangel, M.L. Sundheimer, E. Tucker, G.D. Boreman, M.B. Raschke, Optical dielectric function of silver. Phys. Rev. B 91(23), 235137 (2015). doi:10.1103/PhysRevB.91.235137 [14] S. Liu, P. Zhang, W. Liu, S. Gong, R. Zhong, Y. Zhang, M. Hu, Surface polariton cherenkov light radiation source. Phys. Rev. Lett. 109(15), 153902 (2012). doi:10.1103/PhysRevLett.109.153902 [15] P.A. Belov, Y. Hao, Subwavelength imaging at optical frequencies using a transmission device formed by a periodic layered metaldielectric structure operating in the canalization regime. Phys. Rev. B 73(11), 113110 (2006). doi:10.1103/PhysRevB.73.113110 [16] B. Wood, J.B. Pendry, D.P. Tsai, Directed subwavelength imaging using a layered metaldielectric system. Phys. Rev. B 74(11), 115116 (2006). doi:10.1103/PhysRevB.74.115116 [17] A.V. Zayats, I.I. Smolyaninov, A.A. Maradudin, Nanooptics of surface plasmon polaritons. Phys. Rep. 408(34), 131314 (2005). doi:10.1016/j.physrep.2004.11.001 [18] D.E. Aspnes, A.A. Studna, Dielectric functions and optical parameters of Si, Ge, GaP, GaAs, GaSb, InP, InAs, and InSb from 1.5 to 6.0 eV. Phys. Rev. B 27(2), 9851009 (1983). doi:10.1103/PhysRevB.27.985 [19] F.J.G. de Abajo, Optical excitations in electron microscopy. Rev. Mod. Phys. 82(1), 209275 (2010). doi:10.1103/RevModPhys.82.209 [20] S. Liu, M. Hu, Y. Zhang, W. Liu, P. Zhang, J. Zhou, Theoretical investigation of a tunable freeelectron light source. Phys. Rev. E 83(6), 066609 (2011). doi:10.1103/PhysRevE.83.066609 [21] J. Zhou, M. Hu, Y. Zhang, P. Zhang, W. Liu, S. Liu, Numerical analysis of electroninduced surface plasmon excitation using the FDTD method. J. Opt. 13(3), 035003 (2011). doi:10.1088/20408978/13/3/035003 [22] J.M. Pitarke, V.M. Silkin, E.V. Chulkov, P.M. Echenique, Theory of surface plasmons and surfaceplasmon polaritons. Rep. Prog. Phys. 70(1), 187 (2006). doi:10.1088/00344885/70/1/R01 [23] W.L. Barnes, A. Dereux, T.W. Ebbesen, Surface plasmon subwavelength optics. Nature 424, 824830 (2003). doi:10.1038/nature01937 
References
[1] S.A. Maier, H.A. Atwater, Plasmonics: Localization and guiding of electromagnetic energy in metal/dielectric structures. J. Appl. Phys. 98, 011101 (2005). doi:10.1063/1.1951057
[2] W. Yan, L.F. Shen, L.X. Ran, J.A. Kong, Surface modes at the interfaces between isotropic media and indefinite media. J. Opt. Soc. Am. A 24(2), 530535 (2007). doi:10.1364/JOSAA.24.000530
[3] D. Zhang, Q. Zhang, Y. Lu, Y. Yao, S. Li, J. Jiang, G.L. Liu, Q. Liu, Peptide functionalized nanoplasmonic sensor for explosive detection. NanoMicro Lett. 8(1), 3643 (2016). doi:10.1007/s408200150059z
[4] S. Zeng, K.V. Sreekanth, J. Shang, T. Yu, C. Chen et al., Graphene–gold metasurface architectures for ultrasensitive plasmonic biosensing. Adv. Mater. 27(40), 61636169 (2015). doi:10.1002/adma.201501754
[5] O. Takayama, D. Artigas, L. Torner, Lossless directional guiding of light in dielectric nanosheets using Dyakonov surface waves. Nat. Nanotechnol. 9(6), 419424 (2014). doi:10.1038/nnano.2014.90
[6] M. Sun, T. Sun, Y. Liu, L. Zhu, F. Liu, Y. Huang, C.C. Hasnain, Integrated Plasmonic Refractive Index Sensor Based on Grating/Metal Film Resonant Structure, Proc. SPIE 9757, High Contrast Metastructures V, (March 15, 2016): SPIE, 97570Q (2016). doi:10.1117/12.2218558
[7] H.T.M. Baltar, K. DrozdowiczTomsia, E.M. Goldys, Plasmonics Principles and Applications (K. Y. Kim, Eds), InTech, Rijeka, pp. 136155 (2012).
[8] J.T. Kim, J.J. Ju, S. Park, M. Kim, S.K. Park, M.H. Lee, Chiptochip optical interconnect using gold longrange surface plasmon polariton waveguides. Opt. Express 16(17), 1313313138 (2008). doi:10.1364/OE.16.013133
[9] Y. Li, H. Zhang, T. Mei, N. Zhu, D.H. Zhang, J. Teng, Effect of dielectric cladding on active plasmonic device based on InGaAsP multiple quantum wells. Opt. Express 22(21), 2559925607 (2014). doi:10.1364/OE.22.025599
[10] P. Shekhar, J. Atkinson, Z. Jacob, Hyperbolic metamaterials: fundamentals and applications. Nano Convergence 1(1), 14 (2014). doi:10.1186/s4058001400146
[11] G. Ghosh, Dispersionequation coefficients for the refractive index and birefringence of calcite and quartz crystals. Opt. Commun. 163(13), 95102 (1999). doi:10.1016/S00304018(99)000917
[12] S.A. Maier, Plasmonics: Fundamentals and Applications, Springer, Berlin, pp 534 (2007).
[13] H.U. Yang, J. D'Archangel, M.L. Sundheimer, E. Tucker, G.D. Boreman, M.B. Raschke, Optical dielectric function of silver. Phys. Rev. B 91(23), 235137 (2015). doi:10.1103/PhysRevB.91.235137
[14] S. Liu, P. Zhang, W. Liu, S. Gong, R. Zhong, Y. Zhang, M. Hu, Surface polariton cherenkov light radiation source. Phys. Rev. Lett. 109(15), 153902 (2012). doi:10.1103/PhysRevLett.109.153902
[15] P.A. Belov, Y. Hao, Subwavelength imaging at optical frequencies using a transmission device formed by a periodic layered metaldielectric structure operating in the canalization regime. Phys. Rev. B 73(11), 113110 (2006). doi:10.1103/PhysRevB.73.113110
[16] B. Wood, J.B. Pendry, D.P. Tsai, Directed subwavelength imaging using a layered metaldielectric system. Phys. Rev. B 74(11), 115116 (2006). doi:10.1103/PhysRevB.74.115116
[17] A.V. Zayats, I.I. Smolyaninov, A.A. Maradudin, Nanooptics of surface plasmon polaritons. Phys. Rep. 408(34), 131314 (2005). doi:10.1016/j.physrep.2004.11.001
[18] D.E. Aspnes, A.A. Studna, Dielectric functions and optical parameters of Si, Ge, GaP, GaAs, GaSb, InP, InAs, and InSb from 1.5 to 6.0 eV. Phys. Rev. B 27(2), 9851009 (1983). doi:10.1103/PhysRevB.27.985
[19] F.J.G. de Abajo, Optical excitations in electron microscopy. Rev. Mod. Phys. 82(1), 209275 (2010). doi:10.1103/RevModPhys.82.209
[20] S. Liu, M. Hu, Y. Zhang, W. Liu, P. Zhang, J. Zhou, Theoretical investigation of a tunable freeelectron light source. Phys. Rev. E 83(6), 066609 (2011). doi:10.1103/PhysRevE.83.066609
[21] J. Zhou, M. Hu, Y. Zhang, P. Zhang, W. Liu, S. Liu, Numerical analysis of electroninduced surface plasmon excitation using the FDTD method. J. Opt. 13(3), 035003 (2011). doi:10.1088/20408978/13/3/035003
[22] J.M. Pitarke, V.M. Silkin, E.V. Chulkov, P.M. Echenique, Theory of surface plasmons and surfaceplasmon polaritons. Rep. Prog. Phys. 70(1), 187 (2006). doi:10.1088/00344885/70/1/R01
[23] W.L. Barnes, A. Dereux, T.W. Ebbesen, Surface plasmon subwavelength optics. Nature 424, 824830 (2003). doi:10.1038/nature01937
Citation Information
Fengyu Zhou, Fang Liu, Long Xiao, Kaiyu Cui, Xue Feng, Wei Zhang, Yidong Huang, Extending the Frequency Range of Surface Plasmon Polariton Mode with Metamaterial. NanoMicro Lett. (2017) 9: 9. http://dx.doi.org/10.1007/s4082001601108
History
Received: 20 July 2016 / Accepted: 3 September 2016