Abstract

Resonant field enhancement by groups of 16 nm thin gold nanostrip antennas consisting of four strips (widths of 70, 100, and 130 nm) and fixed gap (50, 100, 150, or 200 nm) between them and positioned on a quartz substrate is investigated by reflection spectroscopy and two-photon photoluminescence scanning optical microscopy. We obtain good agreement with theoretical calculated reflection spectra and the investigated two-photon intensity dependence on the nanoantenna configurations and parameters of the illumination showed field enhancements increasing with increasing gaps in each group for the p-polarized (resonant) excitation, whereas these enhancement effects were not observed for the s-polarization (nonresonant) excitation.

© 2009 Optical Society of America

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  1. V.M.Markel and T.F.George, eds., Optics of Nanostructured Materials (Wiley, 2001).
  2. G. T. Boyd, Th. Rasing, J. R. R. Leite, and Y. R. Shen, “Local-field enhancement on rough surfaces of metals, semimetals, and semiconductors with the use of optical second-harmonic generation,” Phys. Rev. B 30, 519-526 (1984), and references therein.
    [CrossRef]
  3. E. J. Sánchez, L. Novotny, and X. S. Xie, “Near-field fluorescence microscopy based on two-photon excitation with metal tips,” Phys. Rev. Lett. 82, 4014-4017 (1999).
    [CrossRef]
  4. A. Hohenau, J. R. Krenn, S. G. Rodrigo, L. Martin-Moreno, F. Garcia-Vidal, J. Beermann, and S. I. Bozhevolnyi, “Spectroscopy and nonlinear microscopy of gold nanoparticle arrays on gold films,” Phys. Rev. B 75, 085104 (2007).
    [CrossRef]
  5. A. K. Sarychev and V. M. Shalaev, “Electromagnetic field fluctuations and optical nonlinearities in metal-dielectric composites,” Phys. Rep. 335, 275-371 (2000).
    [CrossRef]
  6. S. I. Bozhevolnyi, J. Beermann, and V. Coello, “Direct observation of localized second-harmonic enhancement in random metal nanostructures,” Phys. Rev. Lett. 90, 197403 (2003).
    [CrossRef] [PubMed]
  7. J. Beermann and S. I. Bozhevolnyi, “Microscopy of localized second-harmonic enhancement in random metal nanostructures,” Phys. Rev. B 69, 155429 (2004).
    [CrossRef]
  8. J. Beermann, S. M. Novikov, K. Leosson, and S. I. Bozhevolnyi, “Surface enhanced scanning confocal Raman microscopy of Rhodamine 6G from periodic metal nanostructures,” J. Opt. A, Pure Appl. Opt. 11, 075004 (2009).
    [CrossRef]
  9. J. Beermann, S. M. Novikov, K. Leosson, and S. I. Bozhevolnyi, “Surface enhanced Raman imaging: periodic arrays and individual metal nanoparticles,” Opt. Express 17, 12698-12705 (2009).
    [CrossRef] [PubMed]
  10. J. Beermann, S. M. Novikov, T. Søndergaard, A. E. Boltasseva, and S. I. Bozhevolnyi, “Two-photon mapping of localized field enhancements in thin nanostrip antennas,” Opt. Express 16, 17302-17309 (2008).
    [CrossRef] [PubMed]
  11. T. Søndergaard, J. Beermann, A. Boltasseva, and S. I. Bozhevolnyi, “Slow-plasmon resonant-nanostrip antennas: analysis and demonstration,” Phys. Rev. B 77, 115420 (2008).
    [CrossRef]
  12. T. Søndergaard, “Modeling of plasmonic nanostructures: Green's function integral equation methods,” Phys. Status Solidi B 244, 3448-3462 (2007).
    [CrossRef]
  13. J. Beermann and S. I. Bozhevolnyi, “Two-photon luminescence microscopy of field enhancement at gold nanoparticles,” Phys. Status Solidi C 2, 3983-3987 (2005).
    [CrossRef]
  14. J. Beermann, I. P. Radko, A. Boltasseva, and S. I. Bozhevolnyi, “Localized field enhancements in fractal shaped periodic metal nanostructures,” Opt. Express 15, 15234-15241 (2007).
    [CrossRef] [PubMed]
  15. R. W. Boyd, Nonlinear Optics (Academic, 1992).
  16. P. J. Schuck, D. P. Fromm, A. Sundaramurthy, G. S. Kino, and W. E. Moerner, “Improving the mismatch between light and nanoscale objects with gold bowtie nanoantennas,” Phys. Rev. Lett. 94, 017402 (2005).
    [CrossRef] [PubMed]

2009 (2)

J. Beermann, S. M. Novikov, K. Leosson, and S. I. Bozhevolnyi, “Surface enhanced scanning confocal Raman microscopy of Rhodamine 6G from periodic metal nanostructures,” J. Opt. A, Pure Appl. Opt. 11, 075004 (2009).
[CrossRef]

J. Beermann, S. M. Novikov, K. Leosson, and S. I. Bozhevolnyi, “Surface enhanced Raman imaging: periodic arrays and individual metal nanoparticles,” Opt. Express 17, 12698-12705 (2009).
[CrossRef] [PubMed]

2008 (2)

J. Beermann, S. M. Novikov, T. Søndergaard, A. E. Boltasseva, and S. I. Bozhevolnyi, “Two-photon mapping of localized field enhancements in thin nanostrip antennas,” Opt. Express 16, 17302-17309 (2008).
[CrossRef] [PubMed]

T. Søndergaard, J. Beermann, A. Boltasseva, and S. I. Bozhevolnyi, “Slow-plasmon resonant-nanostrip antennas: analysis and demonstration,” Phys. Rev. B 77, 115420 (2008).
[CrossRef]

2007 (3)

T. Søndergaard, “Modeling of plasmonic nanostructures: Green's function integral equation methods,” Phys. Status Solidi B 244, 3448-3462 (2007).
[CrossRef]

A. Hohenau, J. R. Krenn, S. G. Rodrigo, L. Martin-Moreno, F. Garcia-Vidal, J. Beermann, and S. I. Bozhevolnyi, “Spectroscopy and nonlinear microscopy of gold nanoparticle arrays on gold films,” Phys. Rev. B 75, 085104 (2007).
[CrossRef]

J. Beermann, I. P. Radko, A. Boltasseva, and S. I. Bozhevolnyi, “Localized field enhancements in fractal shaped periodic metal nanostructures,” Opt. Express 15, 15234-15241 (2007).
[CrossRef] [PubMed]

2005 (2)

P. J. Schuck, D. P. Fromm, A. Sundaramurthy, G. S. Kino, and W. E. Moerner, “Improving the mismatch between light and nanoscale objects with gold bowtie nanoantennas,” Phys. Rev. Lett. 94, 017402 (2005).
[CrossRef] [PubMed]

J. Beermann and S. I. Bozhevolnyi, “Two-photon luminescence microscopy of field enhancement at gold nanoparticles,” Phys. Status Solidi C 2, 3983-3987 (2005).
[CrossRef]

2004 (1)

J. Beermann and S. I. Bozhevolnyi, “Microscopy of localized second-harmonic enhancement in random metal nanostructures,” Phys. Rev. B 69, 155429 (2004).
[CrossRef]

2003 (1)

S. I. Bozhevolnyi, J. Beermann, and V. Coello, “Direct observation of localized second-harmonic enhancement in random metal nanostructures,” Phys. Rev. Lett. 90, 197403 (2003).
[CrossRef] [PubMed]

2000 (1)

A. K. Sarychev and V. M. Shalaev, “Electromagnetic field fluctuations and optical nonlinearities in metal-dielectric composites,” Phys. Rep. 335, 275-371 (2000).
[CrossRef]

1999 (1)

E. J. Sánchez, L. Novotny, and X. S. Xie, “Near-field fluorescence microscopy based on two-photon excitation with metal tips,” Phys. Rev. Lett. 82, 4014-4017 (1999).
[CrossRef]

1984 (1)

G. T. Boyd, Th. Rasing, J. R. R. Leite, and Y. R. Shen, “Local-field enhancement on rough surfaces of metals, semimetals, and semiconductors with the use of optical second-harmonic generation,” Phys. Rev. B 30, 519-526 (1984), and references therein.
[CrossRef]

Beermann, J.

J. Beermann, S. M. Novikov, K. Leosson, and S. I. Bozhevolnyi, “Surface enhanced scanning confocal Raman microscopy of Rhodamine 6G from periodic metal nanostructures,” J. Opt. A, Pure Appl. Opt. 11, 075004 (2009).
[CrossRef]

J. Beermann, S. M. Novikov, K. Leosson, and S. I. Bozhevolnyi, “Surface enhanced Raman imaging: periodic arrays and individual metal nanoparticles,” Opt. Express 17, 12698-12705 (2009).
[CrossRef] [PubMed]

J. Beermann, S. M. Novikov, T. Søndergaard, A. E. Boltasseva, and S. I. Bozhevolnyi, “Two-photon mapping of localized field enhancements in thin nanostrip antennas,” Opt. Express 16, 17302-17309 (2008).
[CrossRef] [PubMed]

T. Søndergaard, J. Beermann, A. Boltasseva, and S. I. Bozhevolnyi, “Slow-plasmon resonant-nanostrip antennas: analysis and demonstration,” Phys. Rev. B 77, 115420 (2008).
[CrossRef]

A. Hohenau, J. R. Krenn, S. G. Rodrigo, L. Martin-Moreno, F. Garcia-Vidal, J. Beermann, and S. I. Bozhevolnyi, “Spectroscopy and nonlinear microscopy of gold nanoparticle arrays on gold films,” Phys. Rev. B 75, 085104 (2007).
[CrossRef]

J. Beermann, I. P. Radko, A. Boltasseva, and S. I. Bozhevolnyi, “Localized field enhancements in fractal shaped periodic metal nanostructures,” Opt. Express 15, 15234-15241 (2007).
[CrossRef] [PubMed]

J. Beermann and S. I. Bozhevolnyi, “Two-photon luminescence microscopy of field enhancement at gold nanoparticles,” Phys. Status Solidi C 2, 3983-3987 (2005).
[CrossRef]

J. Beermann and S. I. Bozhevolnyi, “Microscopy of localized second-harmonic enhancement in random metal nanostructures,” Phys. Rev. B 69, 155429 (2004).
[CrossRef]

S. I. Bozhevolnyi, J. Beermann, and V. Coello, “Direct observation of localized second-harmonic enhancement in random metal nanostructures,” Phys. Rev. Lett. 90, 197403 (2003).
[CrossRef] [PubMed]

Boltasseva, A.

T. Søndergaard, J. Beermann, A. Boltasseva, and S. I. Bozhevolnyi, “Slow-plasmon resonant-nanostrip antennas: analysis and demonstration,” Phys. Rev. B 77, 115420 (2008).
[CrossRef]

J. Beermann, I. P. Radko, A. Boltasseva, and S. I. Bozhevolnyi, “Localized field enhancements in fractal shaped periodic metal nanostructures,” Opt. Express 15, 15234-15241 (2007).
[CrossRef] [PubMed]

Boltasseva, A. E.

Boyd, G. T.

G. T. Boyd, Th. Rasing, J. R. R. Leite, and Y. R. Shen, “Local-field enhancement on rough surfaces of metals, semimetals, and semiconductors with the use of optical second-harmonic generation,” Phys. Rev. B 30, 519-526 (1984), and references therein.
[CrossRef]

Boyd, R. W.

R. W. Boyd, Nonlinear Optics (Academic, 1992).

Bozhevolnyi, S. I.

J. Beermann, S. M. Novikov, K. Leosson, and S. I. Bozhevolnyi, “Surface enhanced scanning confocal Raman microscopy of Rhodamine 6G from periodic metal nanostructures,” J. Opt. A, Pure Appl. Opt. 11, 075004 (2009).
[CrossRef]

J. Beermann, S. M. Novikov, K. Leosson, and S. I. Bozhevolnyi, “Surface enhanced Raman imaging: periodic arrays and individual metal nanoparticles,” Opt. Express 17, 12698-12705 (2009).
[CrossRef] [PubMed]

J. Beermann, S. M. Novikov, T. Søndergaard, A. E. Boltasseva, and S. I. Bozhevolnyi, “Two-photon mapping of localized field enhancements in thin nanostrip antennas,” Opt. Express 16, 17302-17309 (2008).
[CrossRef] [PubMed]

T. Søndergaard, J. Beermann, A. Boltasseva, and S. I. Bozhevolnyi, “Slow-plasmon resonant-nanostrip antennas: analysis and demonstration,” Phys. Rev. B 77, 115420 (2008).
[CrossRef]

A. Hohenau, J. R. Krenn, S. G. Rodrigo, L. Martin-Moreno, F. Garcia-Vidal, J. Beermann, and S. I. Bozhevolnyi, “Spectroscopy and nonlinear microscopy of gold nanoparticle arrays on gold films,” Phys. Rev. B 75, 085104 (2007).
[CrossRef]

J. Beermann, I. P. Radko, A. Boltasseva, and S. I. Bozhevolnyi, “Localized field enhancements in fractal shaped periodic metal nanostructures,” Opt. Express 15, 15234-15241 (2007).
[CrossRef] [PubMed]

J. Beermann and S. I. Bozhevolnyi, “Two-photon luminescence microscopy of field enhancement at gold nanoparticles,” Phys. Status Solidi C 2, 3983-3987 (2005).
[CrossRef]

J. Beermann and S. I. Bozhevolnyi, “Microscopy of localized second-harmonic enhancement in random metal nanostructures,” Phys. Rev. B 69, 155429 (2004).
[CrossRef]

S. I. Bozhevolnyi, J. Beermann, and V. Coello, “Direct observation of localized second-harmonic enhancement in random metal nanostructures,” Phys. Rev. Lett. 90, 197403 (2003).
[CrossRef] [PubMed]

Coello, V.

S. I. Bozhevolnyi, J. Beermann, and V. Coello, “Direct observation of localized second-harmonic enhancement in random metal nanostructures,” Phys. Rev. Lett. 90, 197403 (2003).
[CrossRef] [PubMed]

Fromm, D. P.

P. J. Schuck, D. P. Fromm, A. Sundaramurthy, G. S. Kino, and W. E. Moerner, “Improving the mismatch between light and nanoscale objects with gold bowtie nanoantennas,” Phys. Rev. Lett. 94, 017402 (2005).
[CrossRef] [PubMed]

Garcia-Vidal, F.

A. Hohenau, J. R. Krenn, S. G. Rodrigo, L. Martin-Moreno, F. Garcia-Vidal, J. Beermann, and S. I. Bozhevolnyi, “Spectroscopy and nonlinear microscopy of gold nanoparticle arrays on gold films,” Phys. Rev. B 75, 085104 (2007).
[CrossRef]

Hohenau, A.

A. Hohenau, J. R. Krenn, S. G. Rodrigo, L. Martin-Moreno, F. Garcia-Vidal, J. Beermann, and S. I. Bozhevolnyi, “Spectroscopy and nonlinear microscopy of gold nanoparticle arrays on gold films,” Phys. Rev. B 75, 085104 (2007).
[CrossRef]

Kino, G. S.

P. J. Schuck, D. P. Fromm, A. Sundaramurthy, G. S. Kino, and W. E. Moerner, “Improving the mismatch between light and nanoscale objects with gold bowtie nanoantennas,” Phys. Rev. Lett. 94, 017402 (2005).
[CrossRef] [PubMed]

Krenn, J. R.

A. Hohenau, J. R. Krenn, S. G. Rodrigo, L. Martin-Moreno, F. Garcia-Vidal, J. Beermann, and S. I. Bozhevolnyi, “Spectroscopy and nonlinear microscopy of gold nanoparticle arrays on gold films,” Phys. Rev. B 75, 085104 (2007).
[CrossRef]

Leite, J. R. R.

G. T. Boyd, Th. Rasing, J. R. R. Leite, and Y. R. Shen, “Local-field enhancement on rough surfaces of metals, semimetals, and semiconductors with the use of optical second-harmonic generation,” Phys. Rev. B 30, 519-526 (1984), and references therein.
[CrossRef]

Leosson, K.

J. Beermann, S. M. Novikov, K. Leosson, and S. I. Bozhevolnyi, “Surface enhanced scanning confocal Raman microscopy of Rhodamine 6G from periodic metal nanostructures,” J. Opt. A, Pure Appl. Opt. 11, 075004 (2009).
[CrossRef]

J. Beermann, S. M. Novikov, K. Leosson, and S. I. Bozhevolnyi, “Surface enhanced Raman imaging: periodic arrays and individual metal nanoparticles,” Opt. Express 17, 12698-12705 (2009).
[CrossRef] [PubMed]

Martin-Moreno, L.

A. Hohenau, J. R. Krenn, S. G. Rodrigo, L. Martin-Moreno, F. Garcia-Vidal, J. Beermann, and S. I. Bozhevolnyi, “Spectroscopy and nonlinear microscopy of gold nanoparticle arrays on gold films,” Phys. Rev. B 75, 085104 (2007).
[CrossRef]

Moerner, W. E.

P. J. Schuck, D. P. Fromm, A. Sundaramurthy, G. S. Kino, and W. E. Moerner, “Improving the mismatch between light and nanoscale objects with gold bowtie nanoantennas,” Phys. Rev. Lett. 94, 017402 (2005).
[CrossRef] [PubMed]

Novikov, S. M.

Novotny, L.

E. J. Sánchez, L. Novotny, and X. S. Xie, “Near-field fluorescence microscopy based on two-photon excitation with metal tips,” Phys. Rev. Lett. 82, 4014-4017 (1999).
[CrossRef]

Radko, I. P.

Rasing, Th.

G. T. Boyd, Th. Rasing, J. R. R. Leite, and Y. R. Shen, “Local-field enhancement on rough surfaces of metals, semimetals, and semiconductors with the use of optical second-harmonic generation,” Phys. Rev. B 30, 519-526 (1984), and references therein.
[CrossRef]

Rodrigo, S. G.

A. Hohenau, J. R. Krenn, S. G. Rodrigo, L. Martin-Moreno, F. Garcia-Vidal, J. Beermann, and S. I. Bozhevolnyi, “Spectroscopy and nonlinear microscopy of gold nanoparticle arrays on gold films,” Phys. Rev. B 75, 085104 (2007).
[CrossRef]

Sánchez, E. J.

E. J. Sánchez, L. Novotny, and X. S. Xie, “Near-field fluorescence microscopy based on two-photon excitation with metal tips,” Phys. Rev. Lett. 82, 4014-4017 (1999).
[CrossRef]

Sarychev, A. K.

A. K. Sarychev and V. M. Shalaev, “Electromagnetic field fluctuations and optical nonlinearities in metal-dielectric composites,” Phys. Rep. 335, 275-371 (2000).
[CrossRef]

Schuck, P. J.

P. J. Schuck, D. P. Fromm, A. Sundaramurthy, G. S. Kino, and W. E. Moerner, “Improving the mismatch between light and nanoscale objects with gold bowtie nanoantennas,” Phys. Rev. Lett. 94, 017402 (2005).
[CrossRef] [PubMed]

Shalaev, V. M.

A. K. Sarychev and V. M. Shalaev, “Electromagnetic field fluctuations and optical nonlinearities in metal-dielectric composites,” Phys. Rep. 335, 275-371 (2000).
[CrossRef]

Shen, Y. R.

G. T. Boyd, Th. Rasing, J. R. R. Leite, and Y. R. Shen, “Local-field enhancement on rough surfaces of metals, semimetals, and semiconductors with the use of optical second-harmonic generation,” Phys. Rev. B 30, 519-526 (1984), and references therein.
[CrossRef]

Søndergaard, T.

T. Søndergaard, J. Beermann, A. Boltasseva, and S. I. Bozhevolnyi, “Slow-plasmon resonant-nanostrip antennas: analysis and demonstration,” Phys. Rev. B 77, 115420 (2008).
[CrossRef]

J. Beermann, S. M. Novikov, T. Søndergaard, A. E. Boltasseva, and S. I. Bozhevolnyi, “Two-photon mapping of localized field enhancements in thin nanostrip antennas,” Opt. Express 16, 17302-17309 (2008).
[CrossRef] [PubMed]

T. Søndergaard, “Modeling of plasmonic nanostructures: Green's function integral equation methods,” Phys. Status Solidi B 244, 3448-3462 (2007).
[CrossRef]

Sundaramurthy, A.

P. J. Schuck, D. P. Fromm, A. Sundaramurthy, G. S. Kino, and W. E. Moerner, “Improving the mismatch between light and nanoscale objects with gold bowtie nanoantennas,” Phys. Rev. Lett. 94, 017402 (2005).
[CrossRef] [PubMed]

Xie, X. S.

E. J. Sánchez, L. Novotny, and X. S. Xie, “Near-field fluorescence microscopy based on two-photon excitation with metal tips,” Phys. Rev. Lett. 82, 4014-4017 (1999).
[CrossRef]

J. Opt. A, Pure Appl. Opt. (1)

J. Beermann, S. M. Novikov, K. Leosson, and S. I. Bozhevolnyi, “Surface enhanced scanning confocal Raman microscopy of Rhodamine 6G from periodic metal nanostructures,” J. Opt. A, Pure Appl. Opt. 11, 075004 (2009).
[CrossRef]

Opt. Express (3)

Phys. Rep. (1)

A. K. Sarychev and V. M. Shalaev, “Electromagnetic field fluctuations and optical nonlinearities in metal-dielectric composites,” Phys. Rep. 335, 275-371 (2000).
[CrossRef]

Phys. Rev. B (4)

J. Beermann and S. I. Bozhevolnyi, “Microscopy of localized second-harmonic enhancement in random metal nanostructures,” Phys. Rev. B 69, 155429 (2004).
[CrossRef]

T. Søndergaard, J. Beermann, A. Boltasseva, and S. I. Bozhevolnyi, “Slow-plasmon resonant-nanostrip antennas: analysis and demonstration,” Phys. Rev. B 77, 115420 (2008).
[CrossRef]

G. T. Boyd, Th. Rasing, J. R. R. Leite, and Y. R. Shen, “Local-field enhancement on rough surfaces of metals, semimetals, and semiconductors with the use of optical second-harmonic generation,” Phys. Rev. B 30, 519-526 (1984), and references therein.
[CrossRef]

A. Hohenau, J. R. Krenn, S. G. Rodrigo, L. Martin-Moreno, F. Garcia-Vidal, J. Beermann, and S. I. Bozhevolnyi, “Spectroscopy and nonlinear microscopy of gold nanoparticle arrays on gold films,” Phys. Rev. B 75, 085104 (2007).
[CrossRef]

Phys. Rev. Lett. (3)

E. J. Sánchez, L. Novotny, and X. S. Xie, “Near-field fluorescence microscopy based on two-photon excitation with metal tips,” Phys. Rev. Lett. 82, 4014-4017 (1999).
[CrossRef]

P. J. Schuck, D. P. Fromm, A. Sundaramurthy, G. S. Kino, and W. E. Moerner, “Improving the mismatch between light and nanoscale objects with gold bowtie nanoantennas,” Phys. Rev. Lett. 94, 017402 (2005).
[CrossRef] [PubMed]

S. I. Bozhevolnyi, J. Beermann, and V. Coello, “Direct observation of localized second-harmonic enhancement in random metal nanostructures,” Phys. Rev. Lett. 90, 197403 (2003).
[CrossRef] [PubMed]

Phys. Status Solidi B (1)

T. Søndergaard, “Modeling of plasmonic nanostructures: Green's function integral equation methods,” Phys. Status Solidi B 244, 3448-3462 (2007).
[CrossRef]

Phys. Status Solidi C (1)

J. Beermann and S. I. Bozhevolnyi, “Two-photon luminescence microscopy of field enhancement at gold nanoparticles,” Phys. Status Solidi C 2, 3983-3987 (2005).
[CrossRef]

Other (2)

V.M.Markel and T.F.George, eds., Optics of Nanostructured Materials (Wiley, 2001).

R. W. Boyd, Nonlinear Optics (Academic, 1992).

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Figures (6)

Fig. 1
Fig. 1

(a) Schematic of groups with nanostrip antennas along with (b) a SEM image of the EBL fabricated structures having nanostrips with a thickness of 16 nm, a width of 70 nm, a length of 5 μ m , and gaps of 150 nm between them.

Fig. 2
Fig. 2

(a),(c),(e) Measured and (b),(d),(f) calculated reflection spectra for groups of 16 nm thin gold strips of 70, 100, and 130 nm widths and gaps changing from 50 to 200 nm by 50 nm steps. The strip widths are (a),(b) 70; (c),(d) 100; and (e),(f) 130 nm.

Fig. 3
Fig. 3

Schematic of the experimental setup for nonlinear scanning optical microscopy working in reflection with a Ti:sapphire laser, optical isolator (OI), half-wave-plate ( λ / 2 ) , polarizer (P), beam splitter (BS), filters F 1 and F 2 , wavelength selective beam splitter (WSBS), objective (L), sample (S) placed on X Y table, analyzers A 1 and A 2 , and photomultiplier tubes (PMTs).

Fig. 4
Fig. 4

(a) FH and (b),(c) TPL images of two groups with nanostrips of 100 nm width and 200 nm gaps obtained at λ = 745   nm for (a),(b) p- and (c) s-polarized excitations as indicated by arrows. The incident powers were (b) 0.15 and (c) 0.3   mW and the maximum TPL signals are (b) 418 and (c) 152   cps .

Fig. 5
Fig. 5

TPL images of groups with strip widths of (a) 70, (b) 100, and (c) 130 nm and fixed 200 nm gap between them for p-polarized excitation and an incident power of 0.15   mW . (d) Averaged and normalized TPL cross sections taken across each group of strips, and with the yellow rectangles indicating the position of 130 nm wide strips relative to the maximum TPL signals being (a) 314 , (b) 418 , and (c) 653   cps .

Fig. 6
Fig. 6

Experimental dependence of the intensity enhancement α from strips of widths of 70, 100, and 130 nm, on (a) the gap between strips for a fixed excitation wavelength of 745 nm and on (b) the wavelength (with a fixed gap of 200 nm).

Equations (1)

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α = S strip P film 2 A film S film P strip 2 A strip ,

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