Abstract

Optical absorbance measurements are presented for discontinuous films of gold, aluminum, and copper as a function of wavelength, polarization, and angle. Anomolous peaks in the absorbance spectra are observed for all three metals. Two peaks are detected for gold, and one peak is detected for both aluminum and copper. Comparison with electromagnetic theory is made on the basis that the microstructures can be modeled as prolate spheroids. The theoretical model is tested experimentally for various minor-to-major-axis ratios of the spheroid.

© 1988 Optical Society of America

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  1. S. Norman, T. Anderson, C. G. Granqvist, O. Hunderi, “Optical properties of discontinuous gold films,” Phys. Rev. B 18, 674 (1978).
    [CrossRef]
  2. R. H. Ritchie, “Surface plasmons in solids,” Surface Sci. 34, 1 (1973).
    [CrossRef]
  3. S. W. Kennerly, J. W. Little, R. J. Warmack, T. L. Ferrell, “Optical properties of heated Ag films,” Phys. Rev. B 25, 2930 (1982).
  4. C. G. Granqvist, O. Hunderi, “Optical properties of ultrafine gold particles,” Phys. Rev. B 16, 3513 (1977).
    [CrossRef]
  5. A. Wokaun, “Surface-enhanced electromagnetic processes,” Solid State Phys. 38, 223 (1984).
    [CrossRef]
  6. J. G. Bergman, D. S. Chemla, P. F. Liao, A. M. Glass, A. Pinczuk, R. M. Hart, D. H. Olson, “Relationship between surface-enhanced Raman scattering and the dielectric properties of aggregated silver films,” Opt Lett. 6, 33 (1981).
    [CrossRef] [PubMed]
  7. J. P. Goudonnet, T. Inagaki, T. L. Ferrell, R. J. Warmack, M. C. Buncick, E. T. Arakawa, “Enhanced Raman scattering from benzoic acid on silver and gold prolate spheroids on large and transparent patterned areas,” Chem. Phys. 106, 225 (1986).
    [CrossRef]
  8. P. F. Liao, A. Wokaun, “Lightning rod effect in surface enhanced Raman scattering,” J. Chem. Phys. 76, 751 (1982).
    [CrossRef]
  9. P. F. Liao, “Silver structures produced by microlithography,” in Surface Enhanced Raman Scattering, R. K. Chang, T. E. Furtak, eds. (Plenum, New York, 1982).
    [CrossRef]
  10. P. F. Liao, M. B. Stern, “Surface-enhanced Raman scattering on gold and aluminum particle arrays,” Opt. Lett. 7, 483 (1982).
    [CrossRef] [PubMed]
  11. M. J. Bloemer, T. L. Ferrell, M. C. Buncick, R. J. Warmack, “Optical properties of submicrometer-size silver needles,” Phys. Rev. B 37, 8015 (1988).
    [CrossRef]
  12. F. Varnier, N. Mayani, G. Rasigni, M. Rasagni, A. Llebaria, “Surface roughness for metallic thin films deposited on various dielectric coatings,” J. Vac. Sci. Technol. 5, 1806 (1987).
    [CrossRef]
  13. Shimadzu UV-250, Shimadzu Scientific Instruments, Inc., Columbia, Md.
  14. P. Royer, J. P. Goudonnet, R. J. Warmack, T. L. Ferrell, “Substrate effects on surface-plasmon spectra in metal-island films,” Phys. Rev. B 35, 3753 (1987).
    [CrossRef]
  15. H. J. Hagemann, W. Gudat, C. Kunz, “Optical constants from the far infrared to the x-ray region: Mg, Al, Cu, Ag, Au, Bi, C, and Al2O3,” J. Opt. Soc. Am. 65, 742 (1975).
    [CrossRef]
  16. C. C. Chang, T. A. Callcott, E. T. Arakawa, “Barrier diffusion and optical properties of the Au–Al2O3–Al thin-film system,” Phys. Rev. B 32, 6138 (1985).
    [CrossRef]
  17. P. E. Baston, “A new surface plasmon resonance in clusters of small aluminum spheres,” Ultramicroscopy 9, 277 (1982).
    [CrossRef]
  18. P. W. Barger, R. K. Chang, H. Massoudi, “Electrodynamic calculations of the surface enhanced electric intensities on large Ag spheroids,” Phys. Rev. B 27, 7251 (1983).
    [CrossRef]
  19. A. Wokaun, “Surface enhancement of optical fields, mechanisms and applications,” Mol. Phys. 56, 1 (1985).
    [CrossRef]

1988 (1)

M. J. Bloemer, T. L. Ferrell, M. C. Buncick, R. J. Warmack, “Optical properties of submicrometer-size silver needles,” Phys. Rev. B 37, 8015 (1988).
[CrossRef]

1987 (2)

F. Varnier, N. Mayani, G. Rasigni, M. Rasagni, A. Llebaria, “Surface roughness for metallic thin films deposited on various dielectric coatings,” J. Vac. Sci. Technol. 5, 1806 (1987).
[CrossRef]

P. Royer, J. P. Goudonnet, R. J. Warmack, T. L. Ferrell, “Substrate effects on surface-plasmon spectra in metal-island films,” Phys. Rev. B 35, 3753 (1987).
[CrossRef]

1986 (1)

J. P. Goudonnet, T. Inagaki, T. L. Ferrell, R. J. Warmack, M. C. Buncick, E. T. Arakawa, “Enhanced Raman scattering from benzoic acid on silver and gold prolate spheroids on large and transparent patterned areas,” Chem. Phys. 106, 225 (1986).
[CrossRef]

1985 (2)

C. C. Chang, T. A. Callcott, E. T. Arakawa, “Barrier diffusion and optical properties of the Au–Al2O3–Al thin-film system,” Phys. Rev. B 32, 6138 (1985).
[CrossRef]

A. Wokaun, “Surface enhancement of optical fields, mechanisms and applications,” Mol. Phys. 56, 1 (1985).
[CrossRef]

1984 (1)

A. Wokaun, “Surface-enhanced electromagnetic processes,” Solid State Phys. 38, 223 (1984).
[CrossRef]

1983 (1)

P. W. Barger, R. K. Chang, H. Massoudi, “Electrodynamic calculations of the surface enhanced electric intensities on large Ag spheroids,” Phys. Rev. B 27, 7251 (1983).
[CrossRef]

1982 (4)

P. F. Liao, M. B. Stern, “Surface-enhanced Raman scattering on gold and aluminum particle arrays,” Opt. Lett. 7, 483 (1982).
[CrossRef] [PubMed]

P. E. Baston, “A new surface plasmon resonance in clusters of small aluminum spheres,” Ultramicroscopy 9, 277 (1982).
[CrossRef]

P. F. Liao, A. Wokaun, “Lightning rod effect in surface enhanced Raman scattering,” J. Chem. Phys. 76, 751 (1982).
[CrossRef]

S. W. Kennerly, J. W. Little, R. J. Warmack, T. L. Ferrell, “Optical properties of heated Ag films,” Phys. Rev. B 25, 2930 (1982).

1981 (1)

J. G. Bergman, D. S. Chemla, P. F. Liao, A. M. Glass, A. Pinczuk, R. M. Hart, D. H. Olson, “Relationship between surface-enhanced Raman scattering and the dielectric properties of aggregated silver films,” Opt Lett. 6, 33 (1981).
[CrossRef] [PubMed]

1978 (1)

S. Norman, T. Anderson, C. G. Granqvist, O. Hunderi, “Optical properties of discontinuous gold films,” Phys. Rev. B 18, 674 (1978).
[CrossRef]

1977 (1)

C. G. Granqvist, O. Hunderi, “Optical properties of ultrafine gold particles,” Phys. Rev. B 16, 3513 (1977).
[CrossRef]

1975 (1)

1973 (1)

R. H. Ritchie, “Surface plasmons in solids,” Surface Sci. 34, 1 (1973).
[CrossRef]

Anderson, T.

S. Norman, T. Anderson, C. G. Granqvist, O. Hunderi, “Optical properties of discontinuous gold films,” Phys. Rev. B 18, 674 (1978).
[CrossRef]

Arakawa, E. T.

J. P. Goudonnet, T. Inagaki, T. L. Ferrell, R. J. Warmack, M. C. Buncick, E. T. Arakawa, “Enhanced Raman scattering from benzoic acid on silver and gold prolate spheroids on large and transparent patterned areas,” Chem. Phys. 106, 225 (1986).
[CrossRef]

C. C. Chang, T. A. Callcott, E. T. Arakawa, “Barrier diffusion and optical properties of the Au–Al2O3–Al thin-film system,” Phys. Rev. B 32, 6138 (1985).
[CrossRef]

Barger, P. W.

P. W. Barger, R. K. Chang, H. Massoudi, “Electrodynamic calculations of the surface enhanced electric intensities on large Ag spheroids,” Phys. Rev. B 27, 7251 (1983).
[CrossRef]

Baston, P. E.

P. E. Baston, “A new surface plasmon resonance in clusters of small aluminum spheres,” Ultramicroscopy 9, 277 (1982).
[CrossRef]

Bergman, J. G.

J. G. Bergman, D. S. Chemla, P. F. Liao, A. M. Glass, A. Pinczuk, R. M. Hart, D. H. Olson, “Relationship between surface-enhanced Raman scattering and the dielectric properties of aggregated silver films,” Opt Lett. 6, 33 (1981).
[CrossRef] [PubMed]

Bloemer, M. J.

M. J. Bloemer, T. L. Ferrell, M. C. Buncick, R. J. Warmack, “Optical properties of submicrometer-size silver needles,” Phys. Rev. B 37, 8015 (1988).
[CrossRef]

Buncick, M. C.

M. J. Bloemer, T. L. Ferrell, M. C. Buncick, R. J. Warmack, “Optical properties of submicrometer-size silver needles,” Phys. Rev. B 37, 8015 (1988).
[CrossRef]

J. P. Goudonnet, T. Inagaki, T. L. Ferrell, R. J. Warmack, M. C. Buncick, E. T. Arakawa, “Enhanced Raman scattering from benzoic acid on silver and gold prolate spheroids on large and transparent patterned areas,” Chem. Phys. 106, 225 (1986).
[CrossRef]

Callcott, T. A.

C. C. Chang, T. A. Callcott, E. T. Arakawa, “Barrier diffusion and optical properties of the Au–Al2O3–Al thin-film system,” Phys. Rev. B 32, 6138 (1985).
[CrossRef]

Chang, C. C.

C. C. Chang, T. A. Callcott, E. T. Arakawa, “Barrier diffusion and optical properties of the Au–Al2O3–Al thin-film system,” Phys. Rev. B 32, 6138 (1985).
[CrossRef]

Chang, R. K.

P. W. Barger, R. K. Chang, H. Massoudi, “Electrodynamic calculations of the surface enhanced electric intensities on large Ag spheroids,” Phys. Rev. B 27, 7251 (1983).
[CrossRef]

Chemla, D. S.

J. G. Bergman, D. S. Chemla, P. F. Liao, A. M. Glass, A. Pinczuk, R. M. Hart, D. H. Olson, “Relationship between surface-enhanced Raman scattering and the dielectric properties of aggregated silver films,” Opt Lett. 6, 33 (1981).
[CrossRef] [PubMed]

Ferrell, T. L.

M. J. Bloemer, T. L. Ferrell, M. C. Buncick, R. J. Warmack, “Optical properties of submicrometer-size silver needles,” Phys. Rev. B 37, 8015 (1988).
[CrossRef]

P. Royer, J. P. Goudonnet, R. J. Warmack, T. L. Ferrell, “Substrate effects on surface-plasmon spectra in metal-island films,” Phys. Rev. B 35, 3753 (1987).
[CrossRef]

J. P. Goudonnet, T. Inagaki, T. L. Ferrell, R. J. Warmack, M. C. Buncick, E. T. Arakawa, “Enhanced Raman scattering from benzoic acid on silver and gold prolate spheroids on large and transparent patterned areas,” Chem. Phys. 106, 225 (1986).
[CrossRef]

S. W. Kennerly, J. W. Little, R. J. Warmack, T. L. Ferrell, “Optical properties of heated Ag films,” Phys. Rev. B 25, 2930 (1982).

Glass, A. M.

J. G. Bergman, D. S. Chemla, P. F. Liao, A. M. Glass, A. Pinczuk, R. M. Hart, D. H. Olson, “Relationship between surface-enhanced Raman scattering and the dielectric properties of aggregated silver films,” Opt Lett. 6, 33 (1981).
[CrossRef] [PubMed]

Goudonnet, J. P.

P. Royer, J. P. Goudonnet, R. J. Warmack, T. L. Ferrell, “Substrate effects on surface-plasmon spectra in metal-island films,” Phys. Rev. B 35, 3753 (1987).
[CrossRef]

J. P. Goudonnet, T. Inagaki, T. L. Ferrell, R. J. Warmack, M. C. Buncick, E. T. Arakawa, “Enhanced Raman scattering from benzoic acid on silver and gold prolate spheroids on large and transparent patterned areas,” Chem. Phys. 106, 225 (1986).
[CrossRef]

Granqvist, C. G.

S. Norman, T. Anderson, C. G. Granqvist, O. Hunderi, “Optical properties of discontinuous gold films,” Phys. Rev. B 18, 674 (1978).
[CrossRef]

C. G. Granqvist, O. Hunderi, “Optical properties of ultrafine gold particles,” Phys. Rev. B 16, 3513 (1977).
[CrossRef]

Gudat, W.

Hagemann, H. J.

Hart, R. M.

J. G. Bergman, D. S. Chemla, P. F. Liao, A. M. Glass, A. Pinczuk, R. M. Hart, D. H. Olson, “Relationship between surface-enhanced Raman scattering and the dielectric properties of aggregated silver films,” Opt Lett. 6, 33 (1981).
[CrossRef] [PubMed]

Hunderi, O.

S. Norman, T. Anderson, C. G. Granqvist, O. Hunderi, “Optical properties of discontinuous gold films,” Phys. Rev. B 18, 674 (1978).
[CrossRef]

C. G. Granqvist, O. Hunderi, “Optical properties of ultrafine gold particles,” Phys. Rev. B 16, 3513 (1977).
[CrossRef]

Inagaki, T.

J. P. Goudonnet, T. Inagaki, T. L. Ferrell, R. J. Warmack, M. C. Buncick, E. T. Arakawa, “Enhanced Raman scattering from benzoic acid on silver and gold prolate spheroids on large and transparent patterned areas,” Chem. Phys. 106, 225 (1986).
[CrossRef]

Kennerly, S. W.

S. W. Kennerly, J. W. Little, R. J. Warmack, T. L. Ferrell, “Optical properties of heated Ag films,” Phys. Rev. B 25, 2930 (1982).

Kunz, C.

Liao, P. F.

P. F. Liao, A. Wokaun, “Lightning rod effect in surface enhanced Raman scattering,” J. Chem. Phys. 76, 751 (1982).
[CrossRef]

P. F. Liao, M. B. Stern, “Surface-enhanced Raman scattering on gold and aluminum particle arrays,” Opt. Lett. 7, 483 (1982).
[CrossRef] [PubMed]

J. G. Bergman, D. S. Chemla, P. F. Liao, A. M. Glass, A. Pinczuk, R. M. Hart, D. H. Olson, “Relationship between surface-enhanced Raman scattering and the dielectric properties of aggregated silver films,” Opt Lett. 6, 33 (1981).
[CrossRef] [PubMed]

P. F. Liao, “Silver structures produced by microlithography,” in Surface Enhanced Raman Scattering, R. K. Chang, T. E. Furtak, eds. (Plenum, New York, 1982).
[CrossRef]

Little, J. W.

S. W. Kennerly, J. W. Little, R. J. Warmack, T. L. Ferrell, “Optical properties of heated Ag films,” Phys. Rev. B 25, 2930 (1982).

Llebaria, A.

F. Varnier, N. Mayani, G. Rasigni, M. Rasagni, A. Llebaria, “Surface roughness for metallic thin films deposited on various dielectric coatings,” J. Vac. Sci. Technol. 5, 1806 (1987).
[CrossRef]

Massoudi, H.

P. W. Barger, R. K. Chang, H. Massoudi, “Electrodynamic calculations of the surface enhanced electric intensities on large Ag spheroids,” Phys. Rev. B 27, 7251 (1983).
[CrossRef]

Mayani, N.

F. Varnier, N. Mayani, G. Rasigni, M. Rasagni, A. Llebaria, “Surface roughness for metallic thin films deposited on various dielectric coatings,” J. Vac. Sci. Technol. 5, 1806 (1987).
[CrossRef]

Norman, S.

S. Norman, T. Anderson, C. G. Granqvist, O. Hunderi, “Optical properties of discontinuous gold films,” Phys. Rev. B 18, 674 (1978).
[CrossRef]

Olson, D. H.

J. G. Bergman, D. S. Chemla, P. F. Liao, A. M. Glass, A. Pinczuk, R. M. Hart, D. H. Olson, “Relationship between surface-enhanced Raman scattering and the dielectric properties of aggregated silver films,” Opt Lett. 6, 33 (1981).
[CrossRef] [PubMed]

Pinczuk, A.

J. G. Bergman, D. S. Chemla, P. F. Liao, A. M. Glass, A. Pinczuk, R. M. Hart, D. H. Olson, “Relationship between surface-enhanced Raman scattering and the dielectric properties of aggregated silver films,” Opt Lett. 6, 33 (1981).
[CrossRef] [PubMed]

Rasagni, M.

F. Varnier, N. Mayani, G. Rasigni, M. Rasagni, A. Llebaria, “Surface roughness for metallic thin films deposited on various dielectric coatings,” J. Vac. Sci. Technol. 5, 1806 (1987).
[CrossRef]

Rasigni, G.

F. Varnier, N. Mayani, G. Rasigni, M. Rasagni, A. Llebaria, “Surface roughness for metallic thin films deposited on various dielectric coatings,” J. Vac. Sci. Technol. 5, 1806 (1987).
[CrossRef]

Ritchie, R. H.

R. H. Ritchie, “Surface plasmons in solids,” Surface Sci. 34, 1 (1973).
[CrossRef]

Royer, P.

P. Royer, J. P. Goudonnet, R. J. Warmack, T. L. Ferrell, “Substrate effects on surface-plasmon spectra in metal-island films,” Phys. Rev. B 35, 3753 (1987).
[CrossRef]

Stern, M. B.

Varnier, F.

F. Varnier, N. Mayani, G. Rasigni, M. Rasagni, A. Llebaria, “Surface roughness for metallic thin films deposited on various dielectric coatings,” J. Vac. Sci. Technol. 5, 1806 (1987).
[CrossRef]

Warmack, R. J.

M. J. Bloemer, T. L. Ferrell, M. C. Buncick, R. J. Warmack, “Optical properties of submicrometer-size silver needles,” Phys. Rev. B 37, 8015 (1988).
[CrossRef]

P. Royer, J. P. Goudonnet, R. J. Warmack, T. L. Ferrell, “Substrate effects on surface-plasmon spectra in metal-island films,” Phys. Rev. B 35, 3753 (1987).
[CrossRef]

J. P. Goudonnet, T. Inagaki, T. L. Ferrell, R. J. Warmack, M. C. Buncick, E. T. Arakawa, “Enhanced Raman scattering from benzoic acid on silver and gold prolate spheroids on large and transparent patterned areas,” Chem. Phys. 106, 225 (1986).
[CrossRef]

S. W. Kennerly, J. W. Little, R. J. Warmack, T. L. Ferrell, “Optical properties of heated Ag films,” Phys. Rev. B 25, 2930 (1982).

Wokaun, A.

A. Wokaun, “Surface enhancement of optical fields, mechanisms and applications,” Mol. Phys. 56, 1 (1985).
[CrossRef]

A. Wokaun, “Surface-enhanced electromagnetic processes,” Solid State Phys. 38, 223 (1984).
[CrossRef]

P. F. Liao, A. Wokaun, “Lightning rod effect in surface enhanced Raman scattering,” J. Chem. Phys. 76, 751 (1982).
[CrossRef]

Chem. Phys. (1)

J. P. Goudonnet, T. Inagaki, T. L. Ferrell, R. J. Warmack, M. C. Buncick, E. T. Arakawa, “Enhanced Raman scattering from benzoic acid on silver and gold prolate spheroids on large and transparent patterned areas,” Chem. Phys. 106, 225 (1986).
[CrossRef]

J. Chem. Phys. (1)

P. F. Liao, A. Wokaun, “Lightning rod effect in surface enhanced Raman scattering,” J. Chem. Phys. 76, 751 (1982).
[CrossRef]

J. Opt. Soc. Am. (1)

J. Vac. Sci. Technol. (1)

F. Varnier, N. Mayani, G. Rasigni, M. Rasagni, A. Llebaria, “Surface roughness for metallic thin films deposited on various dielectric coatings,” J. Vac. Sci. Technol. 5, 1806 (1987).
[CrossRef]

Mol. Phys. (1)

A. Wokaun, “Surface enhancement of optical fields, mechanisms and applications,” Mol. Phys. 56, 1 (1985).
[CrossRef]

Opt Lett. (1)

J. G. Bergman, D. S. Chemla, P. F. Liao, A. M. Glass, A. Pinczuk, R. M. Hart, D. H. Olson, “Relationship between surface-enhanced Raman scattering and the dielectric properties of aggregated silver films,” Opt Lett. 6, 33 (1981).
[CrossRef] [PubMed]

Opt. Lett. (1)

Phys. Rev. B (7)

P. W. Barger, R. K. Chang, H. Massoudi, “Electrodynamic calculations of the surface enhanced electric intensities on large Ag spheroids,” Phys. Rev. B 27, 7251 (1983).
[CrossRef]

P. Royer, J. P. Goudonnet, R. J. Warmack, T. L. Ferrell, “Substrate effects on surface-plasmon spectra in metal-island films,” Phys. Rev. B 35, 3753 (1987).
[CrossRef]

C. C. Chang, T. A. Callcott, E. T. Arakawa, “Barrier diffusion and optical properties of the Au–Al2O3–Al thin-film system,” Phys. Rev. B 32, 6138 (1985).
[CrossRef]

M. J. Bloemer, T. L. Ferrell, M. C. Buncick, R. J. Warmack, “Optical properties of submicrometer-size silver needles,” Phys. Rev. B 37, 8015 (1988).
[CrossRef]

S. Norman, T. Anderson, C. G. Granqvist, O. Hunderi, “Optical properties of discontinuous gold films,” Phys. Rev. B 18, 674 (1978).
[CrossRef]

S. W. Kennerly, J. W. Little, R. J. Warmack, T. L. Ferrell, “Optical properties of heated Ag films,” Phys. Rev. B 25, 2930 (1982).

C. G. Granqvist, O. Hunderi, “Optical properties of ultrafine gold particles,” Phys. Rev. B 16, 3513 (1977).
[CrossRef]

Solid State Phys. (1)

A. Wokaun, “Surface-enhanced electromagnetic processes,” Solid State Phys. 38, 223 (1984).
[CrossRef]

Surface Sci. (1)

R. H. Ritchie, “Surface plasmons in solids,” Surface Sci. 34, 1 (1973).
[CrossRef]

Ultramicroscopy (1)

P. E. Baston, “A new surface plasmon resonance in clusters of small aluminum spheres,” Ultramicroscopy 9, 277 (1982).
[CrossRef]

Other (2)

Shimadzu UV-250, Shimadzu Scientific Instruments, Inc., Columbia, Md.

P. F. Liao, “Silver structures produced by microlithography,” in Surface Enhanced Raman Scattering, R. K. Chang, T. E. Furtak, eds. (Plenum, New York, 1982).
[CrossRef]

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Figures (12)

Fig. 1
Fig. 1

The dielectric function for the two dipole modes of surface-plasmon oscillations on prolate spheroids as a function of shape parameter η. Large values of the shape parameter correspond to spheres, and small values correspond to needles.

Fig. 2
Fig. 2

Micrographs of structures formed by a 200-nm oblique evaporation onto a calcium fluoride layer: a, gold; b, aluminum; c, copper. Samples were coated with a 7-nm layer of gold to prevent charging in the scanning electron micrograph. The observation angle is along the sample normal. The length of the bar corresponds to 199 nm.

Fig. 3
Fig. 3

Absorbance of s-polarized light for sample with gold prolate spheroids. Sample is that of Fig. 2a. Inset indicates incident angles.

Fig. 4
Fig. 4

Experimental absorbance of p-polarized light for the gold prolate spheroids of Fig. 2a.

Fig. 5
Fig. 5

Theoretical absorbance of p-polarized light for gold prolate spheroids with a 0.17 mean axis ratio.

Fig. 6
Fig. 6

Dispersion relation for the resonant dipole modes for a gold prolate spheroid as a function of the minor-to-major-axis ratio. The short-wavelength l = 1, m = 1 mode and the long-wavelength l = 1, m = 0 mode merge for a spherical particle.

Fig. 7
Fig. 7

Experimental absorbance of three samples for p-polarized light incident at 90° with respect to the major axis of the spheroid. The samples were fabricated by evaporating a, 200-; b, 150-; and c, 100-nm mass thicknesses of gold.

Fig. 8
Fig. 8

Theoretical absorbance of p-polarized light for gold prolate spheroids with mean axis ratios of a, 0.17; b, 0.20; and c, 0.28. Angle of incidence is 90° with respect to the major axis of the spheroid.

Fig. 9
Fig. 9

Plot of the dispersion relation for the dipole modes of an aluminum prolate spheroid as a function of the minor-to-major-axis ratio: solid curves, spheroid in vacuum; dashed curves, spheroid in aluminum oxide.

Fig. 10
Fig. 10

Experimental absorbance of the three aluminum samples for p-polarized light incident at 90°: a, 200-; b, 150-; c, 100-nm mass thickness evaporation. The dotted curve shows the typical absorbance of s-polarized light for all three samples.

Fig. 11
Fig. 11

Plot of the dispersion relation for a copper prolate spheroid as a function of the minor-to-major-axis ratio.

Fig. 12
Fig. 12

Experimental absorbance of p-polarized light incident at 90° with respect to the major axes of the spheroids for the three copper samples formed by a, 200-; b, 150-; and c, 100-nm mass thickness evaporation. The dotted curve is the typical absorbance of s-polarized light at any incident angle.

Equations (1)

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( ω ) = l , m ( ω ) = P l , m ( η 0 ) Q l , m ( η ) Q l , m ( η 0 ) P l , m ( η ) | η = η 0 ,

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