## Tunablity of the unconventional Fano resonances in coated nanowires with radial anisotropy |

Optics Express, Vol. 21, Issue 20, pp. 23619-23630 (2013)

http://dx.doi.org/10.1364/OE.21.023619

Acrobat PDF (1167 KB)

### Abstract

We establish full-wave electromagnetic scattering theory to study the near-field and far-field spectra of radially anisotropic coated nanowires. For coated nanowires containing radially anisotropic core and plasmonic shell, unconventional Fano resonances are predicted due to the interference between dipole cloaking mode and dipole resonant mode. In contrast to Z-shaped Fano profile with small modulation depth for coated nanospheres in Argyropoulos *et al*, Phys. Rev. Lett. **108**, 263905 (2012), we predict S-shaped Fano profile with high depth for coated nanowires. An off-resonance field enhancement in the radially anisotropic core is found at the Fano dip, and its’ magnitude is approximately the same as that the one at the low-energy resonant wavelength. Furthermore, with our adjustment of the inner size and the permittivity elements of the anisotropic core, tunable Fano-like profiles can be realized. These results may be useful for potential applications in different fields of nanotechnology.

© 2013 OSA

## 1. Introduction

1. U. Fano, “Effects of configuration interaction on intensities and phase shifts,” Phys. Rev. **124**(6), 1866–1878(1961). [CrossRef]

2. A. E. Miroshnichenko, S. Flach, and Y. S. Kivshar, “Fano resonances in nanoscale structures,” Rev. Mod. Phys. **82**(3), 2257–2298(2010). [CrossRef]

3. B. Luk’yanchuk, N. I. Zheludev, S. A. Maier, N. J. Halas, P. Nordlander, H. Giessen, and C. T. Chong, “The Fano resonance in plasmonic nanostructures and metamaterials,” Nat. Mater. **9**, 707–715(2010). [CrossRef]

4. F. Hao, Y. Sonnefraud, P. V. Dorpe, S. A. Maier, N. J. Halas, and P. Nordlander, “Symmetry breaking in plasmonic nanocavities: subradiant LSPR sensing and a tunable Fano resonance,” Nano Lett. **8**(11), 3983–3988(2008). [CrossRef] [PubMed]

6. Z. Y. Fang, J. Y. Cai, Z. B. Yan, P. Nordlander, N. J. Halas, and X. Zhu, “Removing a wedge from a metallic nanodisk reveals a Fano resonance,” Nano Lett. **11**(10), 4475–4479(2011). [CrossRef] [PubMed]

7. K. C. Woo, L. Shao, H. J. Chen, Y. Liang, J. F. Wang, and H. Q. Lin, “Universal scaling and Fano resonance in the plasmon coupling between gold nanorods,” ACS Nano **5**(7), 5976–5986(2011). [CrossRef] [PubMed]

8. G. Bachelier, I. Russier-Antoine, E. Benichou, C. Jonin, N. Del Fatti, F. Vallee, and P. F. Brevet, “Fano profiles induced by near-field coupling in heterogeneous dimers of gold and silver nanoparticles,” Phys. Rev. Lett. **101**(19), 197401(2008). [CrossRef] [PubMed]

9. Z. J. Yang, Z. S. Zhang, W. Zhang, Z. H. Hao, and Q. Q. Wang, “Twinned Fano interferences induced by hybridized plasmons in Au-Ag nanorod heterodimers,” Appl. Phys. Lett. **96**(13), 131113(2010). [CrossRef]

10. S. Sheikholeslami, Y. W. Jun, P. K. Jain, and A. P. Alivisatos, “Coupling of optical resonances in a compositionally asymmetric plasmonic nanoparticle dimer,” Nano Lett. **10**(7), 2655–2660(2010). [CrossRef] [PubMed]

11. O. Pena-Rodriguez, U. Pal, M. Campoy-Quiles, L. Rodriguez-Fernandez, M. Garriga, and M. I. Alonso, “Enhanced Fano resonance in asymmetrical Au:Ag heterodimers,” J. Phys. Chem. C **115**(14), 6410–6414(2011). [CrossRef]

12. S. Mukherjee, H. Sobhani, J. B. Lassiter, R. Bardhan, P. Nordlander, and N. J. Halas, “Fanoshells: nanoparticles with built-in Fano resonances,” Nano Lett. **10**(7), 2694–2701(2010). [CrossRef] [PubMed]

16. D. J. Wu, S. M. Liang, and X. J. Liu, “A tunable Fano resonance in silver nanoshell with a spherically anisotropic core,” J. Chem. Phys. **136**(3), 034502(2012). [CrossRef] [PubMed]

*et al*established the conditions for observing Fano resonances at elastic light scattering by small spherical particles, and the interactions between the narrow surface quadrupolar resonances and the broad volume dipolar modes lead to the Fano-like profiles [17

17. M. I. Tribelsky, S. Flach, A. E. Miroshnichenko, A. V. Gorbach, and Y. S. Kivshar, “Light scattering by a finite obstacle and Fano resonances,” Phys. Rev. Lett. **100**(4), 043903(2008). [CrossRef] [PubMed]

18. B. S. Luk’yanchuk, A. E. Miroshnichenko, and Y. S. Kivshar, “Fano resonances and topological optics: an interplay of far- and near-field interference phenomena,” J. Opt. **15**(7), 073001 (2013). [CrossRef]

19. M. I. Tribelksy, A. E. Miroshnichenko, and Y. S. Kivshar, “Unconventional Fano resonances in light scattering by small particles,” Europhys. Lett. **97**(4), 44005(2012). [CrossRef]

*et al*investigated light scattering by coated spheres composed of a dispersive plasmonic core and a dielectric shell, and they predicted unconventional Fano effect and off-resonance field enhancement because of the interference between the various plasmonic modes with the same multipole moment inside the shell [20

20. T. J. Arruda, A. S. Martinez, and F. A. Pinheiro, “Unconventional Fano effect and off-resonance field enhancement in plasmonic coated spheres,” Phys. Rev. A **87**(4), 043841(2013). [CrossRef]

*WS*

_{2}nanotubes [21

21. M. Kociak, O. Stephan, L. Henrard, V. Charbois, A. Rothschild, R. Tenne, and C. Colliex, “Experimental evidence of surface-plasmon coupling in anisotropic hollow nanoparticles,” Phys. Rev. Lett. **87**(7), 075501(2001). [CrossRef] [PubMed]

22. D. Taverna, M. Kociak, V. Charbois, and L. Henrard, “Electron energy-loss spectrum of an electron passing near a locally anisotropic nanotube,” Phys. Rev. B **66**(23), 235419(2002). [CrossRef]

23. Q. Cheng, W. X. Jiang, and T. J. Cui, “Spatial power combination for omnidirectional radiation via anisotropic metamaterials,” Phys. Rev. Lett. **108**(21), 213903(2012). [CrossRef] [PubMed]

24. Y. Yuan, N. Wang, and J. H. Lim, “On the omnidirectional radiation via radially anisotropic zero-index metamaterials,” EPL **100**(3), 34005(2012). [CrossRef]

25. S. Xu, X. X. Cheng, R. R. Zhang, H. O. Moser, Z. Shen, Y. Xu, Z. L. Huang, X. M. Zhang, F. X. Yu, B. L. Zhang, and H. S. Chen, “Experimental Demonstration of a free-space cylindrical cloak without superluminal propagation,” Phys. Rev. Lett. **109**(22), 223903(2012). [CrossRef]

27. Y. X. Ni, L. Gao, and C. W. Qiu, “Achieving invisibility of homogeneous cylindrically anisotropic cylinders,” Plasmonics **5**(3), 251–258(2010). [CrossRef]

28. Y. W. Jin, D. L. Gao, and L. Gao, “Plasmonic resonant light scattering by a cylinder with radial anisotropy,” Prog. Electromag. Res. **106**, 335–347(2010). [CrossRef]

29. H. L. Chen and L. Gao, “Anomalous electromagnetic scattering from radially anisotropic nanowires,” Phys. Rev. A **86**(3), 033825(2012). [CrossRef]

30. C. Argyropoulos, P. Y. Chen, F. Monticone, G. D’Aguanno, and A. Alu, “Nonlinear plasmonic cloaks to realize giant all-optical scattering switching,” Phys. Rev. Lett. **108**(26), 263905(2012). [CrossRef] [PubMed]

## 2. Full-wave electromagnetic theory

*a*and the shell of radius

*b*, as shown in Fig. 1. For radial anisotropy, the relative permittivity and permeability tensors of the core and the shell are expressed as in cylindrical coordinates (

*r*,

*θ*,

*z*) [28

28. Y. W. Jin, D. L. Gao, and L. Gao, “Plasmonic resonant light scattering by a cylinder with radial anisotropy,” Prog. Electromag. Res. **106**, 335–347(2010). [CrossRef]

29. H. L. Chen and L. Gao, “Anomalous electromagnetic scattering from radially anisotropic nanowires,” Phys. Rev. A **86**(3), 033825(2012). [CrossRef]

31. X. P. Yu and L. Gao, “Nonlinear dielectric response in partially resonant composites with radial dielectric anisotropy,” Phys. Lett. A **359**(5), 516–522(2006). [CrossRef]

*ε*(

_{r}*μ*), and

_{r}*ε*(

_{θ}*μ*) stand for the relative radial and tangential permittivity (permeability) elements, while

_{θ}*ε*(

_{z}*μ*) corresponds to the element in the z-axis direction.

_{z}*e*

^{−iωt}, the local electric and magnetic fields in the core and shell are written as,

*z*direction, we have

*H*=

_{r}*H*= 0. Then, after some analytical derivations, we obtain the governing equation for the magnetic field

_{θ}*H*, Assuming

_{z}*H*= Φ(

_{z}*r*)

*e*with

^{im}^{θ}*m*being arbitrary integers, the radial function Φ(

*r*) is found to satisfy As a consequence, the incident, transmitted and scattered magnetic fields can be, respectively, expanded as [28

28. Y. W. Jin, D. L. Gao, and L. Gao, “Plasmonic resonant light scattering by a cylinder with radial anisotropy,” Prog. Electromag. Res. **106**, 335–347(2010). [CrossRef]

29. H. L. Chen and L. Gao, “Anomalous electromagnetic scattering from radially anisotropic nanowires,” Phys. Rev. A **86**(3), 033825(2012). [CrossRef]

*J*(

_{n}*x*),

*N*(

_{n}*x*), and

*H*(

_{n}*x*) are

*n*th-order Bessel, Neumann and Hankel functions. In addition, we denote

24. Y. Yuan, N. Wang, and J. H. Lim, “On the omnidirectional radiation via radially anisotropic zero-index metamaterials,” EPL **100**(3), 34005(2012). [CrossRef]

*k*

_{0}=

*ω/c*.

*r*=

*a*and

*r*=

*b*, and are given by,

## 3. near-field and far-field behavior in the quasistatic limit

31. X. P. Yu and L. Gao, “Nonlinear dielectric response in partially resonant composites with radial dielectric anisotropy,” Phys. Lett. A **359**(5), 516–522(2006). [CrossRef]

*ε*=

_{sr}*ε*=

_{st}*ε*. In the quasistatic limit, we have

_{s}*k*→ 0,

_{c}a*k*→ 0, and

_{s}b*k*

_{0}

*b*→ 0.

*ε*(or

_{cr}*ε*). On the contrary, the magnetic fields in the core may be enhanced for

_{c}_{θ}*ε*>

_{cr}*ε*or be weakened for

_{c}_{θ}*ε*<

_{cr}*ε*[31

_{c}_{θ}31. X. P. Yu and L. Gao, “Nonlinear dielectric response in partially resonant composites with radial dielectric anisotropy,” Phys. Lett. A **359**(5), 516–522(2006). [CrossRef]

*D*

_{1}is zero, the system is in the resonant state. As a consequence, one yields, with the aspect ratio

*η*= (

*a/b*)

^{2}.

*D*

_{1}equals zero, i.e., It is of interest to find that, for small values of

*η*, both Eqs. (13) and (14) converge to the same condition, Equation (15) is just the quasistatic Fano-like resonance or anti-resonance condition for the coated nanocylinder. Here we would like to mention that in deriving above equations, we have adopted such approximations as

*J*

_{0}(

*x*) ≈ 1,

*N*

_{0}(

*x*) ≈ 2/

*π*ln (

*x*/2),

*J′*

_{0}(

*x*) ≈ −

*x*/2,

*N′*

_{0}(

*x*) ≈ 2/

*πx*,

*J*

_{1}(

*x*) ≈

*x*/2,

*J′*

_{1}(

*x*) ≈ 1/2, and

*J′*(

_{ν}*x*) ≈

*νJ*(

_{ν}*x*)/

*x*,

*N′*(

_{ν}*x*) ≈ −

*νN*(

_{ν}*x*)/

*x*for a noninteger

*ν*.

## 4. Numerical results

*ω*= 1.367 × 10

_{p}^{16}rad/s and

*ε*

_{∞}= 5 [30

30. C. Argyropoulos, P. Y. Chen, F. Monticone, G. D’Aguanno, and A. Alu, “Nonlinear plasmonic cloaks to realize giant all-optical scattering switching,” Phys. Rev. Lett. **108**(26), 263905(2012). [CrossRef] [PubMed]

*λ*and the aspect ratio

*η*. For the outer radius

*b*much smaller than the incident wavelength

*λ*, as far as the dependence of the extinction spectra on the core permittivity in concerned, we find that it is dependent mainly on the equivalent core permittivity

*ε*(or

_{cr}*ε*). As a consequence, we choose the isotropic core such as

_{c}_{θ}*ε*=

_{cr}*ε*= 2. From Fig. 2(a), it is evident that there are two resonant regions, at which the extinction efficiency can achieve the maximal values. The corresponding two plasmonic antisymmetric and symmetric modes result from the coupling between the dipole plasmon of solid Ag cylinder (cylindrical modes) and that of Ag cavity cylinder (cavity modes) [32

_{c}_{θ}32. E. Prodan, C. Radloff, N. J. Halas, and P. Nordlander, “A hybridization model for the plasmon response of complex nanostructures,” Science **302**(5644), 419–422(2003). [CrossRef] [PubMed]

*b*are embedded in the air medium at the cylindrical-like resonant wavelength

*a*are embedded in the bulk Ag materials at the void-like resonant wavelength

*λ*<

_{cylinder}*λ*, the antisymmetric (or high-energy) coupling mode at

_{cavity}*λ*

_{1−}is dependent on the cylindrical modes much and takes place in the outer interface of the coated cylinder, while the symmetric mode at

*λ*

_{1+}arises in the interface between the anisotropic core and the plasmonic shell. In the quasistatic limit, both the resonant wavelengths

*λ*

_{1−}and

*λ*

_{1+}can be described by Eq. (13) analytically, as shown in Fig. 2(b). The full-wave electromagnetic results are in reasonable agreement with the analytical formula Eq. (13) (see solid red lines). On the contrary, the coated cylinders may be in the cloaking state, where the extinction efficiency takes the minimum and the coated cylinder is transparent [see Fig. 2(c)]. Again, the condition for the dipole cloaking state Eq. (14) in the quasistatic limit describes the numerical results qualitatively. From Fig. 2(c), we can see that the plasmonic cloaking is an inherently nonresonant phenomenon, and thus has a much broader bandwidth than the resonant bandwidths in Fig. 2(b).

2. A. E. Miroshnichenko, S. Flach, and Y. S. Kivshar, “Fano resonances in nanoscale structures,” Rev. Mod. Phys. **82**(3), 2257–2298(2010). [CrossRef]

3. B. Luk’yanchuk, N. I. Zheludev, S. A. Maier, N. J. Halas, P. Nordlander, H. Giessen, and C. T. Chong, “The Fano resonance in plasmonic nanostructures and metamaterials,” Nat. Mater. **9**, 707–715(2010). [CrossRef]

*ε*= 2(

*E*−

*E*)/

_{R}*τ*(

*E*and

_{R}*τ*are the position and width of the resonance),

*σ*

_{0}is a amplitude constant, and

*q*is the asymmetry parameter [13

13. A. E. Miroshnichenko, “Off-resonance field enhancement by spherical nanoshells,” Phys. Rev. A **81**(5), 053818 (2010). [CrossRef]

*q*= −1.98 accurately. Physically, the symmetrical (low-energy) dipolar resonant mode interferes with the dipole (nonresonant) cloaking state, resulting in the Fano-like asymmetrical profile, as shown in Fig. 3(b). To one’s interest, the asymmetric Fano profile for the coated nanocylinders [see Fig. 3(a)] is quite different from that [see Fig. 3(c)] for the coated nanospheres. At first, the Fano profile for the coated cylinders looks like the letter “S” [see the insert of Fig. 3(b)], in which the dip occurs followed by the resonant peak due to the coupling between the dipolar cloaking mode and the dipolar symmetrical low-energy (long-wavelength) resonant mode. On the contrary, the Fano curve for the coated sphere looks like the letter “Z” if one observes it from the right to the left. And Fano resonances for the coated sphere result from the coupling between the dipolar asymmetrical high-energy (short wavelength) resonant mode with the dipolar cloaking mode, which can be easily understood from Fig. 3(d). Secondly, in comparison with the plasmonic coated nanospheres, the coated nanocylinders provide high modulation depth. In case of realistic losses in the metallic shell, the resonant peak is less pronounced, and the Fano-resonance becomes broader, as expected. Incidentally, no matter what for the coated nanospheres or nanocylinders, the Fano mechanism here has distinct difference with the conventional Fano one, in which the bright dipolar mode interferes with the dark quadrupolar or magnetic mode [17

17. M. I. Tribelsky, S. Flach, A. E. Miroshnichenko, A. V. Gorbach, and Y. S. Kivshar, “Light scattering by a finite obstacle and Fano resonances,” Phys. Rev. Lett. **100**(4), 043903(2008). [CrossRef] [PubMed]

*λ*=

*λ*

_{1−}, the surface plasmon field is excited and spreads out over the outer surface of the coated nanocylinders, and the large magnetic field occurs along the incident polarization near the outer surface [see Fig. 4(a)]. This is in accord with our previous analysis on the hybridization model, in which the high-energy resonant mode is dependent much on the cylindrical mode, and takes place mainly near the outer surface. On the other hand, for

*λ*=

*λ*

_{1+}, one observes that the plasmon resonant field is confined around and inside the anisotropic dielectric core [see Fig. 4(c)]. Comparing the field distribution at the Fano dip [see Fig. 4(b)] with that at the Fano resonance [see Fig. 4(c)], we find that the fields around and insides the dielectric core are largely enhanced in both figures, while the fields outside the coated cylinders are quite different. In detail, at the Fano dip [see Fig. 4(b)], most of the plasmon field is confined around the anisotropic core, resulting in much smaller scattering efficiency, while at Fano resonance [or the low-energy resonant wavelength, see Fig. 4(c)], the bright dipolar resonant state still has a large scattering efficiency. Note that the large enhancement of the local fields in the core is quite useful for realizing the large nonlinear optical susceptibility [13

13. A. E. Miroshnichenko, “Off-resonance field enhancement by spherical nanoshells,” Phys. Rev. A **81**(5), 053818 (2010). [CrossRef]

**359**(5), 516–522(2006). [CrossRef]

30. C. Argyropoulos, P. Y. Chen, F. Monticone, G. D’Aguanno, and A. Alu, “Nonlinear plasmonic cloaks to realize giant all-optical scattering switching,” Phys. Rev. Lett. **108**(26), 263905(2012). [CrossRef] [PubMed]

*b*= 100nm. It is evident that with increasing the inner radius

*a*, both the Fano cloaking wavelength and the Fano resonant wavelength

*λ*

_{1+}exhibit appreciable red-shift, which can be qualitatively understood from Fig. 3(b). In addition, the magnitude of the Fano resonant peak becomes strong. This is due to the fact that, the increased core radius or the thin shell can provide the strong coupling between the cylindrical and the cavity modes, resulting in strong Fano peak and even wide Fano profile. Therefore, one yields a tunable Fano-like profile with our adjustment of the inner size

*a*. Actually, since we vary the inner radius

*a*only, the high-energy antisymmetric mode, which takes place around the outer surface, must exhibit weak dependence on the size

*a*. As a consequence, the high-energy resonant wavelength

*λ*

_{1−}and its corresponding magnitude keep almost invariant with increasing

*a*.

*ε*(or

_{cr}*ε*) is varied. It is evident that with increasing

_{c}_{θ}*ε*, the whole Fano-like profile keeps almost invariant except that its location exhibits red-shift slightly. According to above hybridization theory for the coated cylinders, the change of the anisotropic permittivity of the core will have some influence on the long-wavelength dipolar resonant modes and the dipole cloaking modes, and hence the location of the Fano-like profile due to the coupling between the dipolar long-wavelength symmetric modes with the dipolar cloaking modes shifts. Here we would like to mention that such a shift is quite small, and no shift will appear for our further increasing or decreasing

_{cr}*ε*.

_{cr}## 5. Conclusion

33. J. J. Zhang and A. Zayats, “Multiple Fano resonances in single-layere nonconcentric core-shell nanostructures,” Opt. Express **21**(7), 8426–8436(2013). [CrossRef] [PubMed]

34. M. Kauranen and A. V. Zayats, “Nonlinear plasmonics,” Nat. Photonics **6**, 737–748(2012). [CrossRef]

**108**(26), 263905(2012). [CrossRef] [PubMed]

35. J. Butet, G. Bachelier, I. Russier-Antoine, F. Bertorelle, A. Mosset, N. Lascoux, C. Jonin, E. Benichou, and P. F. Brevet, “Nonlinear Fano profiles in the optical second-harmonic generation from silver nanoparticles,” Phys. Rev. B **86**(7), 075430(2012). [CrossRef]

36. T. J. Arruda, F. A. Pinheiro, and A. S. Martinez, “Electromagnetic energy within coated spheres containing dispersive metamaterials,” J. Opt. **14**(6), 065101(2012). [CrossRef]

37. T. J. Arruda and A. S. Martinez, “Electromagnetic energy within a magnetic infinite cylinder and scattering properties for oblique incidence,” J. Opt. Soc. Am. A **27**(7), 1679–1686(2012). [CrossRef]

## Acknowledgments

## References and links

1. | U. Fano, “Effects of configuration interaction on intensities and phase shifts,” Phys. Rev. |

2. | A. E. Miroshnichenko, S. Flach, and Y. S. Kivshar, “Fano resonances in nanoscale structures,” Rev. Mod. Phys. |

3. | B. Luk’yanchuk, N. I. Zheludev, S. A. Maier, N. J. Halas, P. Nordlander, H. Giessen, and C. T. Chong, “The Fano resonance in plasmonic nanostructures and metamaterials,” Nat. Mater. |

4. | F. Hao, Y. Sonnefraud, P. V. Dorpe, S. A. Maier, N. J. Halas, and P. Nordlander, “Symmetry breaking in plasmonic nanocavities: subradiant LSPR sensing and a tunable Fano resonance,” Nano Lett. |

5. | F. Hao, P. Nordlander, Y. Sonnefraud, P. V. Dorpe, and S. A. Maier, “Tunability of subradiant dipolar and Fano-type plasmon resonances in metallic ring/disk cavities: implications for nanoscale optical sensing,” ACS Nano |

6. | Z. Y. Fang, J. Y. Cai, Z. B. Yan, P. Nordlander, N. J. Halas, and X. Zhu, “Removing a wedge from a metallic nanodisk reveals a Fano resonance,” Nano Lett. |

7. | K. C. Woo, L. Shao, H. J. Chen, Y. Liang, J. F. Wang, and H. Q. Lin, “Universal scaling and Fano resonance in the plasmon coupling between gold nanorods,” ACS Nano |

8. | G. Bachelier, I. Russier-Antoine, E. Benichou, C. Jonin, N. Del Fatti, F. Vallee, and P. F. Brevet, “Fano profiles induced by near-field coupling in heterogeneous dimers of gold and silver nanoparticles,” Phys. Rev. Lett. |

9. | Z. J. Yang, Z. S. Zhang, W. Zhang, Z. H. Hao, and Q. Q. Wang, “Twinned Fano interferences induced by hybridized plasmons in Au-Ag nanorod heterodimers,” Appl. Phys. Lett. |

10. | S. Sheikholeslami, Y. W. Jun, P. K. Jain, and A. P. Alivisatos, “Coupling of optical resonances in a compositionally asymmetric plasmonic nanoparticle dimer,” Nano Lett. |

11. | O. Pena-Rodriguez, U. Pal, M. Campoy-Quiles, L. Rodriguez-Fernandez, M. Garriga, and M. I. Alonso, “Enhanced Fano resonance in asymmetrical Au:Ag heterodimers,” J. Phys. Chem. C |

12. | S. Mukherjee, H. Sobhani, J. B. Lassiter, R. Bardhan, P. Nordlander, and N. J. Halas, “Fanoshells: nanoparticles with built-in Fano resonances,” Nano Lett. |

13. | A. E. Miroshnichenko, “Off-resonance field enhancement by spherical nanoshells,” Phys. Rev. A |

14. | O. Pena-Rodriguez and U. Pal, “Au/Ag core-shell nanoparticles: efficient all-plasmonic Fano-resonance generators,” Nanoscale |

15. | H. J. Chen, L. Shao, Y. C. Man, C. M. Zhao, J. F. Wang, and B. C. Yang, “Fano resonance in (gold core)-(dielectric shell) nanostructures without symmetry breaking,” Small |

16. | D. J. Wu, S. M. Liang, and X. J. Liu, “A tunable Fano resonance in silver nanoshell with a spherically anisotropic core,” J. Chem. Phys. |

17. | M. I. Tribelsky, S. Flach, A. E. Miroshnichenko, A. V. Gorbach, and Y. S. Kivshar, “Light scattering by a finite obstacle and Fano resonances,” Phys. Rev. Lett. |

18. | B. S. Luk’yanchuk, A. E. Miroshnichenko, and Y. S. Kivshar, “Fano resonances and topological optics: an interplay of far- and near-field interference phenomena,” J. Opt. |

19. | M. I. Tribelksy, A. E. Miroshnichenko, and Y. S. Kivshar, “Unconventional Fano resonances in light scattering by small particles,” Europhys. Lett. |

20. | T. J. Arruda, A. S. Martinez, and F. A. Pinheiro, “Unconventional Fano effect and off-resonance field enhancement in plasmonic coated spheres,” Phys. Rev. A |

21. | M. Kociak, O. Stephan, L. Henrard, V. Charbois, A. Rothschild, R. Tenne, and C. Colliex, “Experimental evidence of surface-plasmon coupling in anisotropic hollow nanoparticles,” Phys. Rev. Lett. |

22. | D. Taverna, M. Kociak, V. Charbois, and L. Henrard, “Electron energy-loss spectrum of an electron passing near a locally anisotropic nanotube,” Phys. Rev. B |

23. | Q. Cheng, W. X. Jiang, and T. J. Cui, “Spatial power combination for omnidirectional radiation via anisotropic metamaterials,” Phys. Rev. Lett. |

24. | Y. Yuan, N. Wang, and J. H. Lim, “On the omnidirectional radiation via radially anisotropic zero-index metamaterials,” EPL |

25. | S. Xu, X. X. Cheng, R. R. Zhang, H. O. Moser, Z. Shen, Y. Xu, Z. L. Huang, X. M. Zhang, F. X. Yu, B. L. Zhang, and H. S. Chen, “Experimental Demonstration of a free-space cylindrical cloak without superluminal propagation,” Phys. Rev. Lett. |

26. | X. Sheng, H.S. Chen, B. L. Zhang, B. I. Wu, and J. A. Kong, “Route to low-scattering cylindrical cloaks with finite permittivity and permeability,” Phys. Rev. A |

27. | Y. X. Ni, L. Gao, and C. W. Qiu, “Achieving invisibility of homogeneous cylindrically anisotropic cylinders,” Plasmonics |

28. | Y. W. Jin, D. L. Gao, and L. Gao, “Plasmonic resonant light scattering by a cylinder with radial anisotropy,” Prog. Electromag. Res. |

29. | H. L. Chen and L. Gao, “Anomalous electromagnetic scattering from radially anisotropic nanowires,” Phys. Rev. A |

30. | C. Argyropoulos, P. Y. Chen, F. Monticone, G. D’Aguanno, and A. Alu, “Nonlinear plasmonic cloaks to realize giant all-optical scattering switching,” Phys. Rev. Lett. |

31. | X. P. Yu and L. Gao, “Nonlinear dielectric response in partially resonant composites with radial dielectric anisotropy,” Phys. Lett. A |

32. | E. Prodan, C. Radloff, N. J. Halas, and P. Nordlander, “A hybridization model for the plasmon response of complex nanostructures,” Science |

33. | J. J. Zhang and A. Zayats, “Multiple Fano resonances in single-layere nonconcentric core-shell nanostructures,” Opt. Express |

34. | M. Kauranen and A. V. Zayats, “Nonlinear plasmonics,” Nat. Photonics |

35. | J. Butet, G. Bachelier, I. Russier-Antoine, F. Bertorelle, A. Mosset, N. Lascoux, C. Jonin, E. Benichou, and P. F. Brevet, “Nonlinear Fano profiles in the optical second-harmonic generation from silver nanoparticles,” Phys. Rev. B |

36. | T. J. Arruda, F. A. Pinheiro, and A. S. Martinez, “Electromagnetic energy within coated spheres containing dispersive metamaterials,” J. Opt. |

37. | T. J. Arruda and A. S. Martinez, “Electromagnetic energy within a magnetic infinite cylinder and scattering properties for oblique incidence,” J. Opt. Soc. Am. A |

**OCIS Codes**

(160.4760) Materials : Optical properties

(260.0260) Physical optics : Physical optics

(260.2110) Physical optics : Electromagnetic optics

(260.5740) Physical optics : Resonance

(160.3918) Materials : Metamaterials

**ToC Category:**

Physical Optics

**History**

Original Manuscript: August 14, 2013

Revised Manuscript: September 13, 2013

Manuscript Accepted: September 16, 2013

Published: September 26, 2013

**Citation**

H. L. Chen and L. Gao, "Tunablity of the unconventional Fano resonances in coated nanowires with radial anisotropy," Opt. Express **21**, 23619-23630 (2013)

http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-21-20-23619

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