Abstract

We report on optical image contrast for a specific apertureless near-field optical microscope. We demonstrate that the main part of the optical image’s contrast results from the sample’s topography. The coupling mechanism is analyzed, and we show that the microscope can be regarded as an interferometer that sensitively detects near-field components. However, in the basic configuration the reference field of the interferometer is coupled to the topography. Finally, it is demonstrated that, by controlling the phase of the reference field, one can largely decorrelate the optical image from the topography.

© 2000 Optical Society of America

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References

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  1. U. Ch. Fischer, D. W. Pohl, “Observation of single-particle plasmons by near-field optical microscopy,” Phys. Rev. Lett. 62, 458–461 (1989).
    [CrossRef]
  2. Y. Inouye, S. Kawata, “Near-field scanning optical microscope with a metallic probe tip,” Opt. Lett. 19, 159–161 (1994).
    [CrossRef] [PubMed]
  3. P. Gleyzes, A. C. Boccara, R. Bachelot, “Near-field optical microscopy using a metallic vibrating tip,” Ultramicroscopy 57, 318–322 (1995); R. Bachelot, P. Gleyzes, A. C. Boccara, “Reflection-mode scanning near-field optical microscopy using an apertureless metallic tip,” Appl. Opt. 36, 2160–2170 (1997).
    [CrossRef] [PubMed]
  4. F. Zenhausern, M. P. O’Boyle, H. K. Wickramasinghe, “Apertureless near-field optical microscope,” Appl. Phys. Lett. 65, 1623–1625 (1994).
    [CrossRef]
  5. B. Hecht, H. Bielefeld, Y. Inouye, D. W. Pohl, L. Novotny, “Facts and artifacts in near-field optical microscopy,” J. Appl. Phys. 81, 2492–2498 (1997).
    [CrossRef]
  6. V. Sandoghdar, S. Wegscheider, G. Kraush, J. Mlynek, “Reflection scanning near-field microscopy with uncoated fiber tips: How good is the resolution really?” J. Appl. Phys. 81, 2499–2503 (1997).
    [CrossRef]
  7. O. J. F. Martin, C. Girard, “Controlling and tuning strong optical field gradients at a local probe microscope tip apex,” Appl. Phys. Lett. 70, 705–707 (1997).
    [CrossRef]

1997 (3)

B. Hecht, H. Bielefeld, Y. Inouye, D. W. Pohl, L. Novotny, “Facts and artifacts in near-field optical microscopy,” J. Appl. Phys. 81, 2492–2498 (1997).
[CrossRef]

V. Sandoghdar, S. Wegscheider, G. Kraush, J. Mlynek, “Reflection scanning near-field microscopy with uncoated fiber tips: How good is the resolution really?” J. Appl. Phys. 81, 2499–2503 (1997).
[CrossRef]

O. J. F. Martin, C. Girard, “Controlling and tuning strong optical field gradients at a local probe microscope tip apex,” Appl. Phys. Lett. 70, 705–707 (1997).
[CrossRef]

1995 (1)

P. Gleyzes, A. C. Boccara, R. Bachelot, “Near-field optical microscopy using a metallic vibrating tip,” Ultramicroscopy 57, 318–322 (1995); R. Bachelot, P. Gleyzes, A. C. Boccara, “Reflection-mode scanning near-field optical microscopy using an apertureless metallic tip,” Appl. Opt. 36, 2160–2170 (1997).
[CrossRef] [PubMed]

1994 (2)

F. Zenhausern, M. P. O’Boyle, H. K. Wickramasinghe, “Apertureless near-field optical microscope,” Appl. Phys. Lett. 65, 1623–1625 (1994).
[CrossRef]

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

1989 (1)

U. Ch. Fischer, D. W. Pohl, “Observation of single-particle plasmons by near-field optical microscopy,” Phys. Rev. Lett. 62, 458–461 (1989).
[CrossRef]

Bachelot, R.

P. Gleyzes, A. C. Boccara, R. Bachelot, “Near-field optical microscopy using a metallic vibrating tip,” Ultramicroscopy 57, 318–322 (1995); R. Bachelot, P. Gleyzes, A. C. Boccara, “Reflection-mode scanning near-field optical microscopy using an apertureless metallic tip,” Appl. Opt. 36, 2160–2170 (1997).
[CrossRef] [PubMed]

Bielefeld, H.

B. Hecht, H. Bielefeld, Y. Inouye, D. W. Pohl, L. Novotny, “Facts and artifacts in near-field optical microscopy,” J. Appl. Phys. 81, 2492–2498 (1997).
[CrossRef]

Boccara, A. C.

P. Gleyzes, A. C. Boccara, R. Bachelot, “Near-field optical microscopy using a metallic vibrating tip,” Ultramicroscopy 57, 318–322 (1995); R. Bachelot, P. Gleyzes, A. C. Boccara, “Reflection-mode scanning near-field optical microscopy using an apertureless metallic tip,” Appl. Opt. 36, 2160–2170 (1997).
[CrossRef] [PubMed]

Fischer, U. Ch.

U. Ch. Fischer, D. W. Pohl, “Observation of single-particle plasmons by near-field optical microscopy,” Phys. Rev. Lett. 62, 458–461 (1989).
[CrossRef]

Girard, C.

O. J. F. Martin, C. Girard, “Controlling and tuning strong optical field gradients at a local probe microscope tip apex,” Appl. Phys. Lett. 70, 705–707 (1997).
[CrossRef]

Gleyzes, P.

P. Gleyzes, A. C. Boccara, R. Bachelot, “Near-field optical microscopy using a metallic vibrating tip,” Ultramicroscopy 57, 318–322 (1995); R. Bachelot, P. Gleyzes, A. C. Boccara, “Reflection-mode scanning near-field optical microscopy using an apertureless metallic tip,” Appl. Opt. 36, 2160–2170 (1997).
[CrossRef] [PubMed]

Hecht, B.

B. Hecht, H. Bielefeld, Y. Inouye, D. W. Pohl, L. Novotny, “Facts and artifacts in near-field optical microscopy,” J. Appl. Phys. 81, 2492–2498 (1997).
[CrossRef]

Inouye, Y.

B. Hecht, H. Bielefeld, Y. Inouye, D. W. Pohl, L. Novotny, “Facts and artifacts in near-field optical microscopy,” J. Appl. Phys. 81, 2492–2498 (1997).
[CrossRef]

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

Kawata, S.

Kraush, G.

V. Sandoghdar, S. Wegscheider, G. Kraush, J. Mlynek, “Reflection scanning near-field microscopy with uncoated fiber tips: How good is the resolution really?” J. Appl. Phys. 81, 2499–2503 (1997).
[CrossRef]

Martin, O. J. F.

O. J. F. Martin, C. Girard, “Controlling and tuning strong optical field gradients at a local probe microscope tip apex,” Appl. Phys. Lett. 70, 705–707 (1997).
[CrossRef]

Mlynek, J.

V. Sandoghdar, S. Wegscheider, G. Kraush, J. Mlynek, “Reflection scanning near-field microscopy with uncoated fiber tips: How good is the resolution really?” J. Appl. Phys. 81, 2499–2503 (1997).
[CrossRef]

Novotny, L.

B. Hecht, H. Bielefeld, Y. Inouye, D. W. Pohl, L. Novotny, “Facts and artifacts in near-field optical microscopy,” J. Appl. Phys. 81, 2492–2498 (1997).
[CrossRef]

O’Boyle, M. P.

F. Zenhausern, M. P. O’Boyle, H. K. Wickramasinghe, “Apertureless near-field optical microscope,” Appl. Phys. Lett. 65, 1623–1625 (1994).
[CrossRef]

Pohl, D. W.

B. Hecht, H. Bielefeld, Y. Inouye, D. W. Pohl, L. Novotny, “Facts and artifacts in near-field optical microscopy,” J. Appl. Phys. 81, 2492–2498 (1997).
[CrossRef]

U. Ch. Fischer, D. W. Pohl, “Observation of single-particle plasmons by near-field optical microscopy,” Phys. Rev. Lett. 62, 458–461 (1989).
[CrossRef]

Sandoghdar, V.

V. Sandoghdar, S. Wegscheider, G. Kraush, J. Mlynek, “Reflection scanning near-field microscopy with uncoated fiber tips: How good is the resolution really?” J. Appl. Phys. 81, 2499–2503 (1997).
[CrossRef]

Wegscheider, S.

V. Sandoghdar, S. Wegscheider, G. Kraush, J. Mlynek, “Reflection scanning near-field microscopy with uncoated fiber tips: How good is the resolution really?” J. Appl. Phys. 81, 2499–2503 (1997).
[CrossRef]

Wickramasinghe, H. K.

F. Zenhausern, M. P. O’Boyle, H. K. Wickramasinghe, “Apertureless near-field optical microscope,” Appl. Phys. Lett. 65, 1623–1625 (1994).
[CrossRef]

Zenhausern, F.

F. Zenhausern, M. P. O’Boyle, H. K. Wickramasinghe, “Apertureless near-field optical microscope,” Appl. Phys. Lett. 65, 1623–1625 (1994).
[CrossRef]

Appl. Phys. Lett. (2)

F. Zenhausern, M. P. O’Boyle, H. K. Wickramasinghe, “Apertureless near-field optical microscope,” Appl. Phys. Lett. 65, 1623–1625 (1994).
[CrossRef]

O. J. F. Martin, C. Girard, “Controlling and tuning strong optical field gradients at a local probe microscope tip apex,” Appl. Phys. Lett. 70, 705–707 (1997).
[CrossRef]

J. Appl. Phys. (2)

B. Hecht, H. Bielefeld, Y. Inouye, D. W. Pohl, L. Novotny, “Facts and artifacts in near-field optical microscopy,” J. Appl. Phys. 81, 2492–2498 (1997).
[CrossRef]

V. Sandoghdar, S. Wegscheider, G. Kraush, J. Mlynek, “Reflection scanning near-field microscopy with uncoated fiber tips: How good is the resolution really?” J. Appl. Phys. 81, 2499–2503 (1997).
[CrossRef]

Opt. Lett. (1)

Phys. Rev. Lett. (1)

U. Ch. Fischer, D. W. Pohl, “Observation of single-particle plasmons by near-field optical microscopy,” Phys. Rev. Lett. 62, 458–461 (1989).
[CrossRef]

Ultramicroscopy (1)

P. Gleyzes, A. C. Boccara, R. Bachelot, “Near-field optical microscopy using a metallic vibrating tip,” Ultramicroscopy 57, 318–322 (1995); R. Bachelot, P. Gleyzes, A. C. Boccara, “Reflection-mode scanning near-field optical microscopy using an apertureless metallic tip,” Appl. Opt. 36, 2160–2170 (1997).
[CrossRef] [PubMed]

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Figures (5)

Fig. 1
Fig. 1

Schematic of the experimental arrangement: The electric field that is sent back to the detector by the interferometer arm that contains the microscope is A tip + A spe, where A tip is the field scattered by the tip and A spe, is the specular reflection on the sample (see Fig. 2 for details). The electric field that is sent back to the detector by the other interferometer arm—the so-called external arm—is A ext.

Fig. 2
Fig. 2

Magnification of the focal region: The laser beam is focused on the sample and is represented by the circle arcs at the left- and the right-hand sides. The sample topography is Z(r). Because the tip is fixed, Z(r) represents the sample’s vertical motion, which maintains a constant local tip-to-sample gap when the scanned position is r. The field backscattered by the tip is A tip. The field that is reflected by the large illuminated sample area is A spe, and its phase depth depends on the sample’s vertical motion Z(r).

Fig. 3
Fig. 3

Raw images with dimensions of 1.4 µm × 0.6 µm of a hexagonal Cr pattern on glass, as obtained by vacuum deposition of 20 nm of Cr on a compact array of 220-nm latex spheres and subsequent removal of the latex spheres. (a) The topographic image and (b) the simultaneously recorded optical image (the optical signal is demodulated at the tip’s dithering frequency). The gray scale for image (a) represents topography variations between 0 and 30 nm. The gray scale for image (b) represents the optical signal amplitudes (after the lock-in amplifier), which range between 6.5 and 8.2 V. The arrow in (a) highlights a typical merged-Cr area.

Fig. 4
Fig. 4

Image with dimensions of 0.22 µm × 0.22 µm of the same Cr pattern shown in Fig. 3: (a) The topographic image and (b) the variation of the dc part of the optical signal when a reference field is added. The intensity of the reference field was close to that of the specular reflection of the sample. The gray scale for (a) represents topography variations between 0 and 30 nm. The gray scale for (b) represents optical signal amplitudes that range between 0.2 and 0.5 V.

Fig. 5
Fig. 5

Images with dimensions of 0.93 µm × 0.83 µm of the sample shown in Figs. 3 and 4: (a) The topographic image of the sample and (b) an image of (a) on which a mask of bright circularly shaped dots has been superimposed. (c) The optical image of the sample and (d) an image of (c) on which a bright mask of elliptically shaped dots has been superimposed. (e) Schematic of the masks of both (b) and (d) combined, with the color difference added for better visibility. The bright spots of (c) are located at the center of the hexagons of (a). The optical signals were obtained by interference with a strong field in the external arm. The gray scale for (a) represents topography variations between 0 and 30 nm and that for (c) variations of the optical signal amplitudes (after the lock-in amplifier) between 0.8 and 1.2 V. The masks were added to permit easy comparisons of the patterns of the topographic and the optical images. In (d) the bright patterns indicating merged-Cr areas that are clearly visible in the upper left-hand side of (a) were included to show that the corresponding locations in (c) are almost dark in comparison (see text).

Equations (9)

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IX, Y=|Aspe+Atip+Aext|2.
ztipt=zm cosωt,
ϕX, Y=2kZX, Y,
AspeX, Y=aspe expiϕX, Y,
IX, Y, t=|Atip+Aspe|2.
IωX, Y=AωX, Yaspe* exp-iϕX, Y+cc,
IdcX, Y=|Aext+AspeX, Y|2=|Aext|2+|aspe|2+Aext*aspe expiϕX, Y+cc,
Aref=Aext+aspe expiϕX, YAext,
IωX, YAωX, YAext*+cc.

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