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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 19, Iss. 8 — Apr. 11, 2011
  • pp: 7726–7733
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Direct imaging of nanogap-mode plasmon-resonant fields

Yoshito Tanaka, Hiroyasu Ishiguro, Hideki Fujiwara, Yukie Yokota, Kosei Ueno, Hiroaki Misawa, and Keiji Sasaki  »View Author Affiliations


Optics Express, Vol. 19, Issue 8, pp. 7726-7733 (2011)
http://dx.doi.org/10.1364/OE.19.007726


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Abstract

We perform direct local-field imaging of a plasmon-resonant gold nanoparticle pair separated by a gap of several nanometers using a scattering-type near-field optical microscope with a sharp silicon tip of atomic force microscope. The sharp tip allows the access for the nanogap and the high spatial resolution. Our results provide experimental evidence that the nanogap structure produces an optical spot with the size of a single nanometer (< 10 nm). This is not only of fundamental importance in the field of nanophotonics, but also provide significant information for the development of plasmonic devices with the nanogap structures.

© 2011 OSA

Localized surface plasmons (LSPs) of metal nanoparticles and engineered nanostructures have attracted much attention as an approach to overcome the optical diffraction limit [1

1. S. A. Maier, P. G. Kik, H. A. Atwater, S. Meltzer, E. Harel, B. E. Koel, and A. A. G. Requicha, “Local detection of electromagnetic energy transport below the diffraction limit in metal nanoparticle plasmon waveguides,” Nat. Mater. 2(4), 229–232 (2003). [CrossRef] [PubMed]

4

4. M. L. Brongersma and P. G. Kik, Surface Plasmon Nanophotonics (Springer, Dordrecht, 2007).

]. They work as effective nanoantennas in the visible and infrared wavelength range due to the optical excitation of LSPs [5

5. S. Kühn, U. Håkanson, L. Rogobete, and V. Sandoghdar, “Enhancement of single-molecule fluorescence using a gold nanoparticle as an optical nanoantenna,” Phys. Rev. Lett. 97(1), 017402 (2006). [CrossRef] [PubMed]

7

7. H. Fischer and O. J. F. Martin, “Engineering the optical response of plasmonic nanoantennas,” Opt. Express 16(12), 9144–9154 (2008). [CrossRef] [PubMed]

], which can efficiently convert propagating light into nanoscale-confined and strongly enhanced optical fields. This downscaling from the diffraction limit to the nanometer dimension is a key element in the development of noble optics and photonics, including optical nanolithography [8

8. W. Srituravanich, N. Fang, C. Sun, Q. Luo, and X. Zhang, “Plasmonic Nanolithography,” Nano Lett. 4(6), 1085–1088 (2004). [CrossRef]

], nanoscale optical microscopy [9

9. T. H. Taminiau, F. D. Stefani, F. B. Segerink, and N. F. Van Hulst, “Optical antennas direct single-molecule emission,” Nat. Photonics 2(4), 234–237 (2008). [CrossRef]

], and nanometric optical tweezers [10

10. A. N. Grigorenko, N. W. Roberts, M. R. Dickinson, and Y. Zhang, “Nanometric optical tweezers based on nanostructured substrates,” Nat. Photonics 2(6), 365–370 (2008). [CrossRef]

].

It has been widely shown that the size, shape, and structure of the nanoantennas determine their optical characteristics, including resonant frequencies, local-field distributions, and field enhancements [12

12. H. Xu, J. Aizpurua, M. Käll, and P. Apell, “Electromagnetic contributions to single-molecule sensitivity in surface-enhanced raman scattering,” Phys. Rev. E Stat. Phys. Plasmas Fluids Relat. Interdiscip. Topics 62(33 Pt B), 4318–4324 (2000). [CrossRef] [PubMed]

,13

13. E. Hao and G. C. Schatz, “Electromagnetic fields around silver nanoparticles and dimers,” J. Chem. Phys. 120(1), 357–366 (2004). [CrossRef] [PubMed]

]. In particular, many calculations have suggested that plasmon-resonant nanoantennas composed of a pair of metal nanoparticles with a gap below 10 nm (“nanogap”) produce an intense optical spot that is about two orders of magnitude smaller than the wavelength of the light. This effect is understood as the result of the strong coupling of plasmons between the nanoparticles [7

7. H. Fischer and O. J. F. Martin, “Engineering the optical response of plasmonic nanoantennas,” Opt. Express 16(12), 9144–9154 (2008). [CrossRef] [PubMed]

,11

11. M. Inoue and K. Ohtaka, “Surface Enhanced Raman Scattering by Metal Spheres. I. Cluster Effect,” J. Phys. Soc. Jpn. 52(11), 3853–3864 (1983). [CrossRef]

13

13. E. Hao and G. C. Schatz, “Electromagnetic fields around silver nanoparticles and dimers,” J. Chem. Phys. 120(1), 357–366 (2004). [CrossRef] [PubMed]

]. Nanogap antennas have led to the wide range of physically interesting and technologically important phenomena, such as single-molecule surface-enhanced Raman scattering [14

14. H. Xu, E. J. Bjerneld, M. Käll, and L. Borjesson, “Spectroscopy of single hemoglobin molecules by surface enhanced Raman scattering,” Phys. Rev. Lett. 83(21), 4357–4360 (1999). [CrossRef]

], nonlinear photochemical reactions induced by an incoherent excitation source [15

15. K. Ueno, S. Juodkazis, T. Shibuya, Y. Yokota, V. Mizeikis, K. Sasaki, and H. Misawa, “Nanoparticle plasmon-assisted two-photon polymerization induced by incoherent excitation source,” J. Am. Chem. Soc. 130(22), 6928–6929 (2008). [CrossRef] [PubMed]

], and optical trapping of single molecules [16

16. H. Xu and M. Käll, “Surface-plasmon-enhanced optical forces in silver nanoaggregates,” Phys. Rev. Lett. 89(24), 246802 (2002). [CrossRef] [PubMed]

]. For the understanding of these nanogap-induced phenomena and the applications in nanooptics and nanophotonics, it is important to determine the spatial characteristics of the photon localization within the nanogap experimentally with a single nanometer resolution. Unfortunately, such experiment remains as a challenging task.

The schematic of the scattering-type NSOM is shown in Fig. 1
Fig. 1 Direct near-field imaging of optical nanoantennas with a scattering-type NSOM. The nanoantennas are illuminated under the focused TIR conditions. The confined plasmonic fields are scattered by the sharp AFM tip and transformed to propagating waves during the scanning operation. The near-field and the topography images are obtained simultaneously. The inset shows SEM image of the AFM tip apex [30]. Bar = 180 nm.
[31

31. H. Fujiwara, Y. Tanaka, H. Ishiguro, A. Saito, and K. Sasaki, “Direct observation of localized fields in nanogaps between metal particles,” Appl. Phys. Express 2(10), 102002 (2009). [CrossRef]

]. The extremely sharp AFM tip was used to probe the nanoantennas. The samples were illuminated with laser light at the wavelength of 800 nm under a focused total internal reflection (TIR). Therefore, both topographic and scattered near-field images can be obtained simultaneously. A continuous-wave Ti:sapphire laser beam (wavelength = 800 nm, linewidth = 100 kHz) was used for surface plasmon excitation. The linearly polarized beam was introduced into an inverted optical microscope and was focused by an oil-immersion objective (100 × , numerical aperture = 1.35). A section of the focused beam with the incident angle smaller than the critical angle was masked by a knife edge at the pupil plane of the imaging system; therefore, the sample was illuminated under the focused TIR condition (spot area = 1.2 × 1.7 µm). The TIR illumination technique prevents from being directly heated by the transmitted laser light and greatly reduces the signal background [20

20. Y.-K. Kim, J. B. Ketterson, and D. J. Morgan, “Scanning plasmon optical microscope operation in atomic force microscope mode,” Opt. Lett. 21(3), 165–167 (1996). [CrossRef] [PubMed]

,32

32. B. D. Mangum, C. Mu, and J. M. Gerton, “Resolving single fluorophores within dense ensembles: contrast limits of tip-enhanced fluorescence microscopy,” Opt. Express 16(9), 6183–6193 (2008). [CrossRef] [PubMed]

]. The laser beam was polarized in the parallel direction to the sample surface, i.e., s-polarization along the X-direction in Fig. 1. This polarization could efficiently excite the nanogap-mode plasmon of the dimer nanoantennas. An AFM was placed on the sample stage, and the silicon probe tip was driven at the resonant frequency of the AFM probe. Back-scattered light from the tip was collected by the same objective and detected by a photomultiplier tube (PMT) with a pinhole. This detection configuration allows the efficient measurement of in-plane near-field component (parallel to the sample surface) compared with the vertical component Ez along the Z-direction in Figure. 1. The in-plane component Ex along the X-direction is dominant in the plasmonic fields within the nanogap [25

25. M. Schnell, A. Garcia-Etxarri, J. Alkorta, J. Aizpurua, and R. Hillenbrand, “Phase-resolved mapping of the near-field vector and polarization state in nanoscale antenna gaps,” Nano Lett. 10(9), 3524–3528 (2010). [CrossRef] [PubMed]

]. The detected signal was demodulated at the second harmonic (~700 kHz) of the resonant frequency of the AFM probe by a lock-in amplifier, which can suppress the scattered light signal from the probe shaft and the sample [32

32. B. D. Mangum, C. Mu, and J. M. Gerton, “Resolving single fluorophores within dense ensembles: contrast limits of tip-enhanced fluorescence microscopy,” Opt. Express 16(9), 6183–6193 (2008). [CrossRef] [PubMed]

,33

33. P. G. Gucciardi, G. Bachelier, and M. Allegrini, “Far-field background suppression in tip-modulated apertureless near-field optical microscopy,” J. Appl. Phys. 99(12), 124309 (2006). [CrossRef]

]. We note that the out put of the lock-in amplifer is proportional to the near-field amplitude rather than its intensity due to the interference between the scattered near-field and the far-field background [34

34. B. Knoll and F. Keilmann, “Electromagnetic fields in the cutoff regime of tapered metallic waveguides,” Opt. Commun. 162(4-6), 177–181 (1999). [CrossRef]

].

The metal-coated AFM probe tips, which are normally used in the conventional scattering-type NSOMs [21

21. Z. H. Kim and S. R. Leone, “Polarization-selective mapping of near-field intensity and phase around gold nanoparticles using apertureless near-field microscopy,” Opt. Express 16(3), 1733–1741 (2008). [CrossRef] [PubMed]

28

28. D.-S. Kim, J. Heo, S.-H. Ahn, S. W. Han, W. S. Yun, and Z. H. Kim, “Real-space mapping of the strongly coupled plasmons of nanoparticle dimers,” Nano Lett. 9(10), 3619–3625 (2009). [CrossRef] [PubMed]

,35

35. Y. Inouye and S. Kawata, “Near-field scanning optical microscope with a metallic probe tip,” Opt. Lett. 19(3), 159–161 (1994). [CrossRef] [PubMed]

], can greatly improve the scattered near-field signal. However, the metal-coated tips also restrict the spatial resolution to ~20 nm and limit the access into the gap of single nanometer-scale antennas. Therefore, we chose bare silicon AFM probe tips (SSS-NCH Nanosensors from NanoWorld AG (Switzerland)) that feature a very small tip radius of curvature (typically 2 nm) and a high aspect ratio near the apex (full cone angle < 8° at the 50 nm of the pointed end of the tip). Compared to the metal-coated tips, the perturbation in the local-field distribution for the silicon tip was minified because plasmon resonances at visible wavelengths for the silicon tips are not significant.

The AFM topography and the scattered near-field images for a single 50-nm gold nanosphere are shown in Figs. 2A
Fig. 2 Near-field image of a simple dipole nanoantenna. Topography (A) and corresponding scattered near-field images (B) of a single gold nanosphere. (C) Line profile along the dashed line marked in (B). FWHM of the two peaks are 15.8 nm and 14.2 nm. (D) Calculated near-field distribution of a 50-nm nanosphere with the same excitation as in (B). The image shows the X-component of the electric field in a height of 25 nm above the substrate. Arrows indicate the polarization directions of the incident probe beam. Bar = 100 nm.
and 2B. The nanosphere produces two optical lobes of ~15 nm around both ends along the incident polarization direction (Figs. 2B and 2C). The characteristic represents dipolar near-field distribution and agrees well with the numerical calculation in Fig. 2D. This result demonstrates that our scattering-type NSOM using the sharp silicon AFM tips allows for reliable observation of antenna near-field modes with improved spatial resolution compared to the conventional near-field microscopy [21

21. Z. H. Kim and S. R. Leone, “Polarization-selective mapping of near-field intensity and phase around gold nanoparticles using apertureless near-field microscopy,” Opt. Express 16(3), 1733–1741 (2008). [CrossRef] [PubMed]

29

29. M. Rang, A. C. Jones, F. Zhou, Z. Y. Li, B. J. Wiley, Y. N. Xia, and M. B. Raschke, “Optical near-field mapping of plasmonic nanoprisms,” Nano Lett. 8(10), 3357–3363 (2008). [CrossRef] [PubMed]

].

A dimer nanoantenna composed of a pair of diagonally aligned gold nanoblocks with nanogap is shown in the scanning electron microscope (SEM) image of Fig. 3A
Fig. 3 Dimer nanoantenna with a single nanometer-scale gap. SEM image (A) and experimental scattering spectrum (B) of a single pair of diagonally aligned gold nanoblocks, with an interparticle edge-to-edge separation distance of ~7 nm. The scattering spectrum (B) is normalized by the incident white light intensity. The vertical red line in (B) represents the incident beam wavelength. (C) Calculated near-field distributions of a model gold nanogap antenna; block size = 115 × 115 × 30 nm, curvature radius of each corner = 20 nm, and gap distance = 7 nm. The images show the X- component of the electric field in the X-Y plane at half-height and the X-Z plane along the diagonal line of the antenna. (D) Theoretical scattering spectrum of the same model nanogap antenna as in (C). In the experimental and theoretical scattering spectra, the optical excitation is polarized along the dimer axis.
. The dimer was fabricated on a glass substrate using electron beam lithography and lift-off techniques. The fabrication procedure is described in earlier reports [15

15. K. Ueno, S. Juodkazis, T. Shibuya, Y. Yokota, V. Mizeikis, K. Sasaki, and H. Misawa, “Nanoparticle plasmon-assisted two-photon polymerization induced by incoherent excitation source,” J. Am. Chem. Soc. 130(22), 6928–6929 (2008). [CrossRef] [PubMed]

,17

17. K. Ueno, S. Juodkazis, T. Shibuya, Y. Yokota, V. Mizeikis, K. Sasaki, and H. Misawa, “Nanoparticle-enhanced photopolymerization,” J. Phys. Chem. C 113(27), 11720–11724 (2009). [CrossRef]

]. The gap distance of ~7 nm allowed the AFM probe tip to access the bottom of the nanogap. The block dimension of 115 × 115 × 30 nm was chosen so that the far-field resonance is close to the incident wavelength of 800 nm (see the scattering spectrum in Fig. 3B). The calculated near-field distribution of the nanogap model based on the geometry of Fig. 3A is shown in Fig. 3C. The excitation conditions were also chosen as in the experiments; more specifically, an s-polarized plane wave at a wavelength of 800 nm illuminates the antennas on the glass substrate at an incidence angle of 60° under TIR condition, as shown in Fig. 1. The distribution predicts the presence on optical spot in single nanometer size inside the nanogap. Moreover, the theoretical scattering spectrum of the nanogap model (Fig. 3D) is in good agreement with the experimental data in Fig. 3B.

In conclusion, the direct imaging of nanogap-mode plasmon-resonant fields provides experimental evidence that the nanogap antenna produces a single nanometer-scale optical spot. This result will have a fundamental impact on the field of nanophotonics and promises potential applications of nanogap antennas, including optical imaging, optical spectroscopy, optical lithography, optical data storage, and optical manipulation.

Acknowledgement

The present work was partly supported by the Ministry of Education, Culture, Sports, Science, and Technology of Japan: KAKENHI Grant-in-Aid for Scientific Research on the Priority Area “Strong Photon-Molecule Coupling Fields” (No. 470, 1904900209) and for Young Scientists (B) (2171009009) to Yoshito Tanaka.

References and links

1.

S. A. Maier, P. G. Kik, H. A. Atwater, S. Meltzer, E. Harel, B. E. Koel, and A. A. G. Requicha, “Local detection of electromagnetic energy transport below the diffraction limit in metal nanoparticle plasmon waveguides,” Nat. Mater. 2(4), 229–232 (2003). [CrossRef] [PubMed]

2.

L. Feng, D. Van Orden, M. Abashin, Q. J. Wang, Y. F. Chen, V. Lomakin, and Y. Fainman, “Nanoscale optical field localization by resonantly focused plasmons,” Opt. Express 17(6), 4824–4832 (2009). [CrossRef] [PubMed]

3.

J. A. Schuller, E. S. Barnard, W. Cai, Y. C. Jun, J. S. White, and M. L. Brongersma, “Plasmonics for extreme light concentration and manipulation,” Nat. Mater. 9(3), 193–204 (2010). [CrossRef] [PubMed]

4.

M. L. Brongersma and P. G. Kik, Surface Plasmon Nanophotonics (Springer, Dordrecht, 2007).

5.

S. Kühn, U. Håkanson, L. Rogobete, and V. Sandoghdar, “Enhancement of single-molecule fluorescence using a gold nanoparticle as an optical nanoantenna,” Phys. Rev. Lett. 97(1), 017402 (2006). [CrossRef] [PubMed]

6.

P. Mühlschlegel, H.-J. Eisler, O. J. F. Martin, B. Hecht, and D. W. Pohl, “Resonant optical antennas,” Science 308(5728), 1607–1609 (2005). [CrossRef] [PubMed]

7.

H. Fischer and O. J. F. Martin, “Engineering the optical response of plasmonic nanoantennas,” Opt. Express 16(12), 9144–9154 (2008). [CrossRef] [PubMed]

8.

W. Srituravanich, N. Fang, C. Sun, Q. Luo, and X. Zhang, “Plasmonic Nanolithography,” Nano Lett. 4(6), 1085–1088 (2004). [CrossRef]

9.

T. H. Taminiau, F. D. Stefani, F. B. Segerink, and N. F. Van Hulst, “Optical antennas direct single-molecule emission,” Nat. Photonics 2(4), 234–237 (2008). [CrossRef]

10.

A. N. Grigorenko, N. W. Roberts, M. R. Dickinson, and Y. Zhang, “Nanometric optical tweezers based on nanostructured substrates,” Nat. Photonics 2(6), 365–370 (2008). [CrossRef]

11.

M. Inoue and K. Ohtaka, “Surface Enhanced Raman Scattering by Metal Spheres. I. Cluster Effect,” J. Phys. Soc. Jpn. 52(11), 3853–3864 (1983). [CrossRef]

12.

H. Xu, J. Aizpurua, M. Käll, and P. Apell, “Electromagnetic contributions to single-molecule sensitivity in surface-enhanced raman scattering,” Phys. Rev. E Stat. Phys. Plasmas Fluids Relat. Interdiscip. Topics 62(33 Pt B), 4318–4324 (2000). [CrossRef] [PubMed]

13.

E. Hao and G. C. Schatz, “Electromagnetic fields around silver nanoparticles and dimers,” J. Chem. Phys. 120(1), 357–366 (2004). [CrossRef] [PubMed]

14.

H. Xu, E. J. Bjerneld, M. Käll, and L. Borjesson, “Spectroscopy of single hemoglobin molecules by surface enhanced Raman scattering,” Phys. Rev. Lett. 83(21), 4357–4360 (1999). [CrossRef]

15.

K. Ueno, S. Juodkazis, T. Shibuya, Y. Yokota, V. Mizeikis, K. Sasaki, and H. Misawa, “Nanoparticle plasmon-assisted two-photon polymerization induced by incoherent excitation source,” J. Am. Chem. Soc. 130(22), 6928–6929 (2008). [CrossRef] [PubMed]

16.

H. Xu and M. Käll, “Surface-plasmon-enhanced optical forces in silver nanoaggregates,” Phys. Rev. Lett. 89(24), 246802 (2002). [CrossRef] [PubMed]

17.

K. Ueno, S. Juodkazis, T. Shibuya, Y. Yokota, V. Mizeikis, K. Sasaki, and H. Misawa, “Nanoparticle-enhanced photopolymerization,” J. Phys. Chem. C 113(27), 11720–11724 (2009). [CrossRef]

18.

K. Imura, H. Okamoto, M. K. Hossain, and M. Kitajima, “Visualization of localized intense optical fields in single gold-nanoparticle assemblies and ultrasensitive Raman active sites,” Nano Lett. 6(10), 2173–2176 (2006). [CrossRef] [PubMed]

19.

R. Hillenbrand, F. Keilmann, P. Hanarp, D. S. Sutherland, and J. Aizpurua, “Coherent imaging of nanoscale plasmon patterns with a carbon nanotube optical probe,” Appl. Phys. Lett. 83(2), 368–370 (2003). [CrossRef]

20.

Y.-K. Kim, J. B. Ketterson, and D. J. Morgan, “Scanning plasmon optical microscope operation in atomic force microscope mode,” Opt. Lett. 21(3), 165–167 (1996). [CrossRef] [PubMed]

21.

Z. H. Kim and S. R. Leone, “Polarization-selective mapping of near-field intensity and phase around gold nanoparticles using apertureless near-field microscopy,” Opt. Express 16(3), 1733–1741 (2008). [CrossRef] [PubMed]

22.

R. Esteban, R. Vogelgesang, J. Dorfmüller, A. Dmitriev, C. Rockstuhl, C. Etrich, and K. Kern, “Direct near-field optical imaging of higher order plasmonic resonances,” Nano Lett. 8(10), 3155–3159 (2008). [CrossRef] [PubMed]

23.

R. Hillenbrand and F. Keilmann, “Optical oscillation modes of plasmon particles observed in direct space by phase-contrast near-field microscopy,” Appl. Phys. B 73, 239–243 (2001).

24.

R. L. Olmon, P. M. Krenz, A. C. Jones, G. D. Boreman, and M. B. Raschke, “Near-field imaging of optical antenna modes in the mid-infrared,” Opt. Express 16(25), 20295–20305 (2008). [CrossRef] [PubMed]

25.

M. Schnell, A. Garcia-Etxarri, J. Alkorta, J. Aizpurua, and R. Hillenbrand, “Phase-resolved mapping of the near-field vector and polarization state in nanoscale antenna gaps,” Nano Lett. 10(9), 3524–3528 (2010). [CrossRef] [PubMed]

26.

E. Cubukcu, E. A. Kort, K. B. Crozier, and F. Capasso, “Plasmonic laser antenna,” Appl. Phys. Lett. 89(9), 093120 (2006). [CrossRef]

27.

N. F. Yu, E. Cubukcu, L. Diehl, D. Bour, S. Corzine, J. T. Zhu, G. Höfler, K. B. Crozier, and F. Capasso, “Bowtie plasmonic quantum cascade laser antenna,” Opt. Express 15(20), 13272–13281 (2007). [CrossRef] [PubMed]

28.

D.-S. Kim, J. Heo, S.-H. Ahn, S. W. Han, W. S. Yun, and Z. H. Kim, “Real-space mapping of the strongly coupled plasmons of nanoparticle dimers,” Nano Lett. 9(10), 3619–3625 (2009). [CrossRef] [PubMed]

29.

M. Rang, A. C. Jones, F. Zhou, Z. Y. Li, B. J. Wiley, Y. N. Xia, and M. B. Raschke, “Optical near-field mapping of plasmonic nanoprisms,” Nano Lett. 8(10), 3357–3363 (2008). [CrossRef] [PubMed]

30.

The images were supplied by NANOSENSORS (www.nanosensors.com).

31.

H. Fujiwara, Y. Tanaka, H. Ishiguro, A. Saito, and K. Sasaki, “Direct observation of localized fields in nanogaps between metal particles,” Appl. Phys. Express 2(10), 102002 (2009). [CrossRef]

32.

B. D. Mangum, C. Mu, and J. M. Gerton, “Resolving single fluorophores within dense ensembles: contrast limits of tip-enhanced fluorescence microscopy,” Opt. Express 16(9), 6183–6193 (2008). [CrossRef] [PubMed]

33.

P. G. Gucciardi, G. Bachelier, and M. Allegrini, “Far-field background suppression in tip-modulated apertureless near-field optical microscopy,” J. Appl. Phys. 99(12), 124309 (2006). [CrossRef]

34.

B. Knoll and F. Keilmann, “Electromagnetic fields in the cutoff regime of tapered metallic waveguides,” Opt. Commun. 162(4-6), 177–181 (1999). [CrossRef]

35.

Y. Inouye and S. Kawata, “Near-field scanning optical microscope with a metallic probe tip,” Opt. Lett. 19(3), 159–161 (1994). [CrossRef] [PubMed]

OCIS Codes
(240.6680) Optics at surfaces : Surface plasmons
(220.4241) Optical design and fabrication : Nanostructure fabrication
(180.4243) Microscopy : Near-field microscopy
(250.5403) Optoelectronics : Plasmonics

ToC Category:
Optics at Surfaces

History
Original Manuscript: February 10, 2011
Revised Manuscript: March 10, 2011
Manuscript Accepted: March 29, 2011
Published: April 6, 2011

Citation
Yoshito Tanaka, Hiroyasu Ishiguro, Hideki Fujiwara, Yukie Yokota, Kosei Ueno, Hiroaki Misawa, and Keiji Sasaki, "Direct imaging of nanogap-mode plasmon-resonant fields," Opt. Express 19, 7726-7733 (2011)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-8-7726


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References

  1. S. A. Maier, P. G. Kik, H. A. Atwater, S. Meltzer, E. Harel, B. E. Koel, and A. A. G. Requicha, “Local detection of electromagnetic energy transport below the diffraction limit in metal nanoparticle plasmon waveguides,” Nat. Mater. 2(4), 229–232 (2003). [CrossRef] [PubMed]
  2. L. Feng, D. Van Orden, M. Abashin, Q. J. Wang, Y. F. Chen, V. Lomakin, and Y. Fainman, “Nanoscale optical field localization by resonantly focused plasmons,” Opt. Express 17(6), 4824–4832 (2009). [CrossRef] [PubMed]
  3. J. A. Schuller, E. S. Barnard, W. Cai, Y. C. Jun, J. S. White, and M. L. Brongersma, “Plasmonics for extreme light concentration and manipulation,” Nat. Mater. 9(3), 193–204 (2010). [CrossRef] [PubMed]
  4. M. L. Brongersma and P. G. Kik, Surface Plasmon Nanophotonics (Springer, Dordrecht, 2007).
  5. S. Kühn, U. Håkanson, L. Rogobete, and V. Sandoghdar, “Enhancement of single-molecule fluorescence using a gold nanoparticle as an optical nanoantenna,” Phys. Rev. Lett. 97(1), 017402 (2006). [CrossRef] [PubMed]
  6. P. Mühlschlegel, H.-J. Eisler, O. J. F. Martin, B. Hecht, and D. W. Pohl, “Resonant optical antennas,” Science 308(5728), 1607–1609 (2005). [CrossRef] [PubMed]
  7. H. Fischer and O. J. F. Martin, “Engineering the optical response of plasmonic nanoantennas,” Opt. Express 16(12), 9144–9154 (2008). [CrossRef] [PubMed]
  8. W. Srituravanich, N. Fang, C. Sun, Q. Luo, and X. Zhang, “Plasmonic Nanolithography,” Nano Lett. 4(6), 1085–1088 (2004). [CrossRef]
  9. T. H. Taminiau, F. D. Stefani, F. B. Segerink, and N. F. Van Hulst, “Optical antennas direct single-molecule emission,” Nat. Photonics 2(4), 234–237 (2008). [CrossRef]
  10. A. N. Grigorenko, N. W. Roberts, M. R. Dickinson, and Y. Zhang, “Nanometric optical tweezers based on nanostructured substrates,” Nat. Photonics 2(6), 365–370 (2008). [CrossRef]
  11. M. Inoue and K. Ohtaka, “Surface Enhanced Raman Scattering by Metal Spheres. I. Cluster Effect,” J. Phys. Soc. Jpn. 52(11), 3853–3864 (1983). [CrossRef]
  12. H. Xu, J. Aizpurua, M. Käll, and P. Apell, “Electromagnetic contributions to single-molecule sensitivity in surface-enhanced raman scattering,” Phys. Rev. E Stat. Phys. Plasmas Fluids Relat. Interdiscip. Topics 62(33 Pt B), 4318–4324 (2000). [CrossRef] [PubMed]
  13. E. Hao and G. C. Schatz, “Electromagnetic fields around silver nanoparticles and dimers,” J. Chem. Phys. 120(1), 357–366 (2004). [CrossRef] [PubMed]
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