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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 19, Iss. 3 — Jan. 31, 2011
  • pp: 2626–2633
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Light transmission through nanostructured metallic films: coupling between surface waves and localized resonances

L. Lin and A. Roberts  »View Author Affiliations


Optics Express, Vol. 19, Issue 3, pp. 2626-2633 (2011)
http://dx.doi.org/10.1364/OE.19.002626


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Abstract

We present an experimental and computational investigation of the optical properties of thin metallic films periodically perforated with nanometric apertures and show that high transmission through such a structure is attributable to the localized surface plasmon (LSP) resonances of the aperture. The periodicity-related optical phenomena, including Wood’s anomaly and surface plasmon polariton (SPP) excitation, interfere with LSPs and generate Fano resonances with asymmetric spectral profiles. The transmission maximum of the Fano profile is related to the constructive interference between the LSP field and diffracted light propagating along the surface; the transmission minimum of the Fano profile is caused by the destructive interference between LSPs and SPPs. The study confirms the negative role of SPP in transmission through the structure.

© 2011 OSA

1. Introduction

The initial observation of enhanced optical transmission (EOT) through thin metallic films perforated with subwavelength apertures [1

1. T. W. Ebbesen, H. J. Lezec, H. F. Ghaemi, T. Thio, and P. A. Wolff, “Extraordinary optical transmission through sub-wavelength hole arrays,” Nature 391(6668), 667–669 (1998). [CrossRef]

] has stimulated many fundamental studies as well as application-driven research over the past decade. The phenomenon has been observed in various structures, including perforated and continuous metal films [2

2. I. Avrutsky, Y. Zhao, and V. Kochergin, “Surface-plasmon-assisted resonant tunneling of light through a periodically corrugated thin metal film,” Opt. Lett. 25(9), 595–597 (2000). [CrossRef]

5

5. R. J. Blaikie, L. Lin, and R. J. Reeves, “Plasmon-enhanced optical transmission of nanostructured metallic multilayers,” Int. J. Nanotech. 6(3/4), 222–232 (2009). [CrossRef]

]. While many attributed the excitation of surface plasmon polaritons (SPPs) on two surfaces of the metal film as the origin of this effect [6

6. H. F. Ghaemi, T. Thio, D. E. Grupp, T. W. Ebbesen, and H. J. Lezec, “Surface plasmons enhance optical transmission through subwavelength holes,” Phys. Rev. B 58(11), 6779–6782 (1998). [CrossRef]

8

8. S. A. Darmanyan and A. V. Zayats, “Light tunneling via resonant surface plasmon polariton states and the enhanced transmission of periodically nanostructured metal films: An analytical study,” Phys. Rev. B 67(3), 035424 (2003). [CrossRef]

], others have also suggested that EOT is caused by the interference between diffracted evanescent waves generated by subwavelength features and questioned the role of SPPs in EOT [9

9. M. M. J. Treacy, “Dynamical diffraction in metallic optical gratings,” Appl. Phys. Lett. 75(5), 606–608 (1999). [CrossRef]

11

11. H. J. Lezec and T. Thio, “Diffracted evanescent wave model for enhanced and suppressed optical transmission through subwavelength hole arrays,” Opt. Express 12(16), 3629–3651 (2004). [CrossRef] [PubMed]

]. The debate surrounding this issue emerged from observations of the discrepancy between the theoretical prediction of SPP spectral locations and the observed EOT peak positions [6

6. H. F. Ghaemi, T. Thio, D. E. Grupp, T. W. Ebbesen, and H. J. Lezec, “Surface plasmons enhance optical transmission through subwavelength holes,” Phys. Rev. B 58(11), 6779–6782 (1998). [CrossRef]

].

More recently, the influential role of localized surface plasmons (LSPs) in EOT has been revealed by investigations of metallic films with various aperture shapes [4

4. S. M. Orbons, A. Roberts, D. N. Jamieson, M. I. Haftel, C. Schlockermann, D. Freeman, and B. Luther-Davies, “Extraordinary optical transmission with coaxial apertures,” Appl. Phys. Lett. 90(25), 251107 (2007). [CrossRef]

,12

12. A. Degiron, H. J. Lezec, N. Yamamoto, and T. W. Ebbesen, “Optical transmission properties of a single subwavelength aperture in a real metal,” Opt. Commun. 239(1-3), 61–66 (2004). [CrossRef]

16

16. Y.-W. Jiang, L. D.-C. Tzuang, Y.-H. Ye, Y.-T. Wu, M.-W. Tsai, C.-Y. Chen, and S.-C. Lee, “Effect of Wood’s anomalies on the profile of extraordinary transmission spectra through metal periodic arrays of rectangular subwavelength holes with different aspect ratio,” Opt. Express 17(4), 2631–2637 (2009). [CrossRef] [PubMed]

]. In contrast to the SPP resonances originating from periodicity present within the structure, LSPs are individual resonances occurring within the apertures whose characteristics are sensitive to the aperture geometry and the optical properties of the materials filling the apertures. Complex apertures generally offer higher coupling efficiencies to unpolarized light than simple square or rectangular apertures. For example, it has been demonstrated that cross-shaped holes can provide larger transmission than square or rectangular holes of same surface area [15

15. C.-Y. Chen, M.-W. Tsai, T.-H. Chuang, Y.-T. Chang, and S.-C. Lee, “Extraordinary transmission through a silver film perforated with cross shaped hole arrays in a square lattice,” Appl. Phys. Lett. 91, 063108 ‖2007|. [CrossRef]

], whereas the spectral locations of LSP resonances can be tuned by simply adjusting the widths or lengths of the arms of the crosses [14

14. L. Lin, L. B. Hande, and A. Roberts, “Resonant nanometric cross-shaped apertures: Single apertures versus periodic arrays,” Appl. Phys. Lett. 95, (2009). [PubMed]

,15

15. C.-Y. Chen, M.-W. Tsai, T.-H. Chuang, Y.-T. Chang, and S.-C. Lee, “Extraordinary transmission through a silver film perforated with cross shaped hole arrays in a square lattice,” Appl. Phys. Lett. 91, 063108 ‖2007|. [CrossRef]

]. The interplay between SPP and LSP resonances, along with the scattering and diffraction of incident light by subwavelength features in thin metal films can give rise to rich spectral behaviour. For example, it has been shown that the excitation of Wood’s anomalies (WAs) and SPP resonances can alter the characteristics of the LSP resonances [14

14. L. Lin, L. B. Hande, and A. Roberts, “Resonant nanometric cross-shaped apertures: Single apertures versus periodic arrays,” Appl. Phys. Lett. 95, (2009). [PubMed]

,16

16. Y.-W. Jiang, L. D.-C. Tzuang, Y.-H. Ye, Y.-T. Wu, M.-W. Tsai, C.-Y. Chen, and S.-C. Lee, “Effect of Wood’s anomalies on the profile of extraordinary transmission spectra through metal periodic arrays of rectangular subwavelength holes with different aspect ratio,” Opt. Express 17(4), 2631–2637 (2009). [CrossRef] [PubMed]

,17

17. S. H. Chang, S. K. Gray, and G. C. Schatz, “Surface plasmon generation and light transmission by isolated nanoholes and arrays of nanoholes in thin metal films,” Opt. Express 13(8), 3150–3165 (2005). [CrossRef] [PubMed]

]; and the coupling between scattering and SPP excitation yields the asymmetric Fano resonance [18

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

] line shape and the red-shift of the transmission peaks in the transmission spectrum of hole-array structures [19

19. C. Genet, M. P. van Exter, and J. P. Woerdman, “Fano-type interpretation of red shifts and red tails in hole array transmission spectra,” Opt. Commun. 225(4-6), 331–336 (2003). [CrossRef]

].

2. Spectral responses of periodic aperture arrays

Figure 1
Fig. 1 A schematic of the structure used in this study.
shows a schematic of the structure used in this study, in which p is the lattice constant of the aperture arrays and l and w are the arm-length and the arm-width of the crosses, respectively. Here we assume the incident light propagates along the z-axis with electric field polarized along the y-axis. The aperture arrays were fabricated in a 140-nm-thick gold (Au) film on a glass substrate using focused ion beam milling. Details of the sample fabrication and characterization as well as the finite element method (FEM) based computational investigation, can be found in Ref. 14

14. L. Lin, L. B. Hande, and A. Roberts, “Resonant nanometric cross-shaped apertures: Single apertures versus periodic arrays,” Appl. Phys. Lett. 95, (2009). [PubMed]

. Figure 2
Fig. 2 Measured transmission spectra of four fabricated samples. The geometric parameters of the structure are given in the key. The solid arrows and the triangles show the periodicity-dependent transmission minimum and maximum of interest, respectively.
shows the measured transmission spectra of four aperture arrays of various lattice constants; the detailed geometric parameters of the structure are given in the key. We see that as the period of the structure increases, the location of the transmission maximum of the LSP peak [14

14. L. Lin, L. B. Hande, and A. Roberts, “Resonant nanometric cross-shaped apertures: Single apertures versus periodic arrays,” Appl. Phys. Lett. 95, (2009). [PubMed]

] (dashed arrow), and the location of the transmission minimum (solid arrow) situated just before this peak, shift to longer wavelengths.

3. Field distributions

In Fig. 5(a), the co-existence of LSP resonances and diffracted propagating waves is clearly visible: the LSPs occur on the ridges of the aperture and diffracted field is apparent near the unperforated region on the Au/glass interface. Interference between propagating diffracted orders in the substrate is also apparent. Simulations of field distributions at shorter wavelengths confirm that the co-contribution of LSP excitation and diffraction by periodic apertures gives rise to the additional peak appearing on the short-wavelength side of asymmetric feature in the transmission spectrum of the structure, i.e., the peaks at around 720 nm, 850 nm and 950 nm for structures with a periodicity of 500nm, 600 nm and 700 nm, respectively. This additional peak does not appear in the transmission of the structure with p = 400 nm as it is located outside the spectral range shown in Fig. 3, whereas for the structure with p = 414 nm (green line in Fig. 2) the peak shifts to longer wavelengths and therefore becomes observable in Fig. 2. Nevertheless, the focus of this study is the nature of the asymmetric feature introduced by the periodicity of the structure, which will be revealed in the following discussion.

A clearer picture of the interference between LSPs and surface waves emerges from studies of local field patterns near the Ag/glass interface. Figure 6
Fig. 6 Ez profiles on x-y planes situating at 5 nm above the Au/glass interface in the Ag film (z = + 5 nm) and 5 nm below the interface in the glass substrate (z = −5 nm). Structure geometry: p = 600 nm, w = 40 nm and l = 350 nm. (a) λ = 912 nm, (b) λ = 942 nm and (c) λ = 1240 nm. The colour scales are normalized to the maximum absolute value of Ez on z = + 5 nm plane at λ = 942 nm.
illustrates the Ez profile on x-y planes located at 5 nm above the Au/glass interface in the Au film layer (indicated by z = + 5 nm in the figure) and 5 nm below the interface in the glass substrate layer (indicated as z = −5 nm). Since the aperture geometry affects only the amplitude of the maximum in the asymmetric feature in the spectrum but not its location, we here show the results for a structure with p = 600 nm, l = 350 nm and w = 40 nm, which is the arrangement with a relatively high transmission in the asymmetric feature (as seen in Fig. 2 of Ref 14

14. L. Lin, L. B. Hande, and A. Roberts, “Resonant nanometric cross-shaped apertures: Single apertures versus periodic arrays,” Appl. Phys. Lett. 95, (2009). [PubMed]

). The colour scales shown in Fig. 6 are normalized to the maximum absolute value of Ez on z = + 5 nm plane at λ = 942 nm. Figure 6(a) and 6(b) show Ez at λ = 912 nm (peak) and λ = 942 nm (minimum), respectively. For comparison, Ez at the centre wavelength of the LSP peak (λ = 1240 nm) is also displayed in Fig. 6(c), as the field distributions at this wavelength best resemble the profiles of LSPs occurring in an isolated aperture [14

14. L. Lin, L. B. Hande, and A. Roberts, “Resonant nanometric cross-shaped apertures: Single apertures versus periodic arrays,” Appl. Phys. Lett. 95, (2009). [PubMed]

].

4. Conclusion

Acknowledgments

This research was supported under Australian Research Council's Discovery Projects funding scheme (project number DP0878268).

References and links

1.

T. W. Ebbesen, H. J. Lezec, H. F. Ghaemi, T. Thio, and P. A. Wolff, “Extraordinary optical transmission through sub-wavelength hole arrays,” Nature 391(6668), 667–669 (1998). [CrossRef]

2.

I. Avrutsky, Y. Zhao, and V. Kochergin, “Surface-plasmon-assisted resonant tunneling of light through a periodically corrugated thin metal film,” Opt. Lett. 25(9), 595–597 (2000). [CrossRef]

3.

H. J. Lezec, A. Degiron, E. Devaux, R. A. Linke, L. Martin-Moreno, F. J. Garcia-Vidal, and T. W. Ebbesen, “Beaming light from a subwavelength aperture,” Science 297(5582), 820–822 (2002). [CrossRef] [PubMed]

4.

S. M. Orbons, A. Roberts, D. N. Jamieson, M. I. Haftel, C. Schlockermann, D. Freeman, and B. Luther-Davies, “Extraordinary optical transmission with coaxial apertures,” Appl. Phys. Lett. 90(25), 251107 (2007). [CrossRef]

5.

R. J. Blaikie, L. Lin, and R. J. Reeves, “Plasmon-enhanced optical transmission of nanostructured metallic multilayers,” Int. J. Nanotech. 6(3/4), 222–232 (2009). [CrossRef]

6.

H. F. Ghaemi, T. Thio, D. E. Grupp, T. W. Ebbesen, and H. J. Lezec, “Surface plasmons enhance optical transmission through subwavelength holes,” Phys. Rev. B 58(11), 6779–6782 (1998). [CrossRef]

7.

L. Martín-Moreno, F. J. García-Vidal, H. J. Lezec, K. M. Pellerin, T. Thio, J. B. Pendry, and T. W. Ebbesen, “Theory of extraordinary optical transmission through subwavelength hole arrays,” Phys. Rev. Lett. 86(6), 1114–1117 (2001). [CrossRef] [PubMed]

8.

S. A. Darmanyan and A. V. Zayats, “Light tunneling via resonant surface plasmon polariton states and the enhanced transmission of periodically nanostructured metal films: An analytical study,” Phys. Rev. B 67(3), 035424 (2003). [CrossRef]

9.

M. M. J. Treacy, “Dynamical diffraction in metallic optical gratings,” Appl. Phys. Lett. 75(5), 606–608 (1999). [CrossRef]

10.

Q. Cao and P. Lalanne, “Negative role of surface plasmons in the transmission of metallic gratings with very narrow slits,” Phys. Rev. Lett. 88(5), 057403 (2002). [CrossRef] [PubMed]

11.

H. J. Lezec and T. Thio, “Diffracted evanescent wave model for enhanced and suppressed optical transmission through subwavelength hole arrays,” Opt. Express 12(16), 3629–3651 (2004). [CrossRef] [PubMed]

12.

A. Degiron, H. J. Lezec, N. Yamamoto, and T. W. Ebbesen, “Optical transmission properties of a single subwavelength aperture in a real metal,” Opt. Commun. 239(1-3), 61–66 (2004). [CrossRef]

13.

K. J. K. Koerkamp, S. Enoch, F. B. Segerink, N. F. van Hulst, and L. Kuipers, “Strong influence of hole shape on extraordinary transmission through periodic arrays of subwavelength holes,” Phys. Rev. Lett. 92(18), 183901 (2004). [CrossRef] [PubMed]

14.

L. Lin, L. B. Hande, and A. Roberts, “Resonant nanometric cross-shaped apertures: Single apertures versus periodic arrays,” Appl. Phys. Lett. 95, (2009). [PubMed]

15.

C.-Y. Chen, M.-W. Tsai, T.-H. Chuang, Y.-T. Chang, and S.-C. Lee, “Extraordinary transmission through a silver film perforated with cross shaped hole arrays in a square lattice,” Appl. Phys. Lett. 91, 063108 ‖2007|. [CrossRef]

16.

Y.-W. Jiang, L. D.-C. Tzuang, Y.-H. Ye, Y.-T. Wu, M.-W. Tsai, C.-Y. Chen, and S.-C. Lee, “Effect of Wood’s anomalies on the profile of extraordinary transmission spectra through metal periodic arrays of rectangular subwavelength holes with different aspect ratio,” Opt. Express 17(4), 2631–2637 (2009). [CrossRef] [PubMed]

17.

S. H. Chang, S. K. Gray, and G. C. Schatz, “Surface plasmon generation and light transmission by isolated nanoholes and arrays of nanoholes in thin metal films,” Opt. Express 13(8), 3150–3165 (2005). [CrossRef] [PubMed]

18.

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

19.

C. Genet, M. P. van Exter, and J. P. Woerdman, “Fano-type interpretation of red shifts and red tails in hole array transmission spectra,” Opt. Commun. 225(4-6), 331–336 (2003). [CrossRef]

20.

Y. Xie, A. R. Zakharian, J. V. Moloney, and M. Mansuripur, “Transmission of light through periodic arrays of sub-wavelength slits in metallic hosts,” Opt. Express 14(14), 6400–6413 (2006). [CrossRef] [PubMed]

21.

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(9), 707–715 (2010). [CrossRef] [PubMed]

OCIS Codes
(240.6680) Optics at surfaces : Surface plasmons
(240.6690) Optics at surfaces : Surface waves
(050.6624) Diffraction and gratings : Subwavelength structures

ToC Category:
Diffraction and Gratings

History
Original Manuscript: November 29, 2010
Revised Manuscript: January 14, 2011
Manuscript Accepted: January 16, 2011
Published: January 27, 2011

Citation
L. Lin and A. Roberts, "Light transmission through nanostructured metallic films: coupling between surface waves and localized resonances," Opt. Express 19, 2626-2633 (2011)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-3-2626


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References

  1. T. W. Ebbesen, H. J. Lezec, H. F. Ghaemi, T. Thio, and P. A. Wolff, “Extraordinary optical transmission through sub-wavelength hole arrays,” Nature 391(6668), 667–669 (1998). [CrossRef]
  2. I. Avrutsky, Y. Zhao, and V. Kochergin, “Surface-plasmon-assisted resonant tunneling of light through a periodically corrugated thin metal film,” Opt. Lett. 25(9), 595–597 (2000). [CrossRef]
  3. H. J. Lezec, A. Degiron, E. Devaux, R. A. Linke, L. Martin-Moreno, F. J. Garcia-Vidal, and T. W. Ebbesen, “Beaming light from a subwavelength aperture,” Science 297(5582), 820–822 (2002). [CrossRef] [PubMed]
  4. S. M. Orbons, A. Roberts, D. N. Jamieson, M. I. Haftel, C. Schlockermann, D. Freeman, and B. Luther-Davies, “Extraordinary optical transmission with coaxial apertures,” Appl. Phys. Lett. 90(25), 251107 (2007). [CrossRef]
  5. R. J. Blaikie, L. Lin, and R. J. Reeves, “Plasmon-enhanced optical transmission of nanostructured metallic multilayers,” Int. J. Nanotech. 6(3/4), 222–232 (2009). [CrossRef]
  6. H. F. Ghaemi, T. Thio, D. E. Grupp, T. W. Ebbesen, and H. J. Lezec, “Surface plasmons enhance optical transmission through subwavelength holes,” Phys. Rev. B 58(11), 6779–6782 (1998). [CrossRef]
  7. L. Martín-Moreno, F. J. García-Vidal, H. J. Lezec, K. M. Pellerin, T. Thio, J. B. Pendry, and T. W. Ebbesen, “Theory of extraordinary optical transmission through subwavelength hole arrays,” Phys. Rev. Lett. 86(6), 1114–1117 (2001). [CrossRef] [PubMed]
  8. S. A. Darmanyan and A. V. Zayats, “Light tunneling via resonant surface plasmon polariton states and the enhanced transmission of periodically nanostructured metal films: An analytical study,” Phys. Rev. B 67(3), 035424 (2003). [CrossRef]
  9. M. M. J. Treacy, “Dynamical diffraction in metallic optical gratings,” Appl. Phys. Lett. 75(5), 606–608 (1999). [CrossRef]
  10. Q. Cao and P. Lalanne, “Negative role of surface plasmons in the transmission of metallic gratings with very narrow slits,” Phys. Rev. Lett. 88(5), 057403 (2002). [CrossRef] [PubMed]
  11. H. J. Lezec and T. Thio, “Diffracted evanescent wave model for enhanced and suppressed optical transmission through subwavelength hole arrays,” Opt. Express 12(16), 3629–3651 (2004). [CrossRef] [PubMed]
  12. A. Degiron, H. J. Lezec, N. Yamamoto, and T. W. Ebbesen, “Optical transmission properties of a single subwavelength aperture in a real metal,” Opt. Commun. 239(1-3), 61–66 (2004). [CrossRef]
  13. K. J. K. Koerkamp, S. Enoch, F. B. Segerink, N. F. van Hulst, and L. Kuipers, “Strong influence of hole shape on extraordinary transmission through periodic arrays of subwavelength holes,” Phys. Rev. Lett. 92(18), 183901 (2004). [CrossRef] [PubMed]
  14. L. Lin, L. B. Hande, and A. Roberts, “Resonant nanometric cross-shaped apertures: Single apertures versus periodic arrays,” Appl. Phys. Lett. 95, (2009). [PubMed]
  15. C.-Y. Chen, M.-W. Tsai, T.-H. Chuang, Y.-T. Chang, and S.-C. Lee, “Extraordinary transmission through a silver film perforated with cross shaped hole arrays in a square lattice,” Appl. Phys. Lett. 91, 063108 ‖2007|. [CrossRef]
  16. Y.-W. Jiang, L. D.-C. Tzuang, Y.-H. Ye, Y.-T. Wu, M.-W. Tsai, C.-Y. Chen, and S.-C. Lee, “Effect of Wood’s anomalies on the profile of extraordinary transmission spectra through metal periodic arrays of rectangular subwavelength holes with different aspect ratio,” Opt. Express 17(4), 2631–2637 (2009). [CrossRef] [PubMed]
  17. S. H. Chang, S. K. Gray, and G. C. Schatz, “Surface plasmon generation and light transmission by isolated nanoholes and arrays of nanoholes in thin metal films,” Opt. Express 13(8), 3150–3165 (2005). [CrossRef] [PubMed]
  18. U. Fano, “Effects of configuration interaction on intensities and phase shifts,” Phys. Rev. 124(6), 1866–1878 (1961). [CrossRef]
  19. C. Genet, M. P. van Exter, and J. P. Woerdman, “Fano-type interpretation of red shifts and red tails in hole array transmission spectra,” Opt. Commun. 225(4-6), 331–336 (2003). [CrossRef]
  20. Y. Xie, A. R. Zakharian, J. V. Moloney, and M. Mansuripur, “Transmission of light through periodic arrays of sub-wavelength slits in metallic hosts,” Opt. Express 14(14), 6400–6413 (2006). [CrossRef] [PubMed]
  21. 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(9), 707–715 (2010). [CrossRef] [PubMed]

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