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Optics Letters

Optics Letters


  • Vol. 29, Iss. 19 — Oct. 1, 2004
  • pp: 2306–2308

Spot-size reduction in terahertz apertureless near-field imaging

P. C. M. Planken and N. C. J. van der Valk  »View Author Affiliations

Optics Letters, Vol. 29, Issue 19, pp. 2306-2308 (2004)

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We show measurements and calculations of the terahertz (THz) near field of a metal tip with a specially formed, semicircular apex that allows us to identify the separate contributions of the tip apex and shaft to the measured signal. We find that when the tip–crystal distance is not modulated the measured near-field signal is overwhelmed by contributions from the tip shaft, resulting in a relatively large THz spot size. When the tip–crystal distance is modulated, with subsequent lock-in detection at the modulation frequency, only the near-field distribution of the semicircular apex is observed, resulting in a much smaller THz spot size and thus improved spatial resolution.

© 2004 Optical Society of America

OCIS Codes
(110.3080) Imaging systems : Infrared imaging
(180.5810) Microscopy : Scanning microscopy
(300.6370) Spectroscopy : Spectroscopy, microwave
(320.7160) Ultrafast optics : Ultrafast technology

P. C. M. Planken and N. C. J. van der Valk, "Spot-size reduction in terahertz apertureless near-field imaging," Opt. Lett. 29, 2306-2308 (2004)

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  1. N. C. J. van der Valk and P. C. M. Planken, Appl. Phys. Lett. 81, 1558 (2002).
  2. K. Wang, A. Barkan, and D. M. Mittleman, Appl. Phys. Lett. 84, 305 (2004).
  3. H.-T. Chen, R. Kersting, and G. C. Cho, Appl. Phys. Lett. 83, 3009 (2003).
  4. B. Knoll and F. Keilmann, Opt. Commun. 182, 321 (2000).
  5. R. Hillenbrand, T. Taubner, and F. Keilmann, Nature 418, 159 (2002).
  6. R. Fikri, T. Grosges, and D. Barchiesi, Opt. Lett. 28, 2147 (2003).
  7. C. A. Balanis, Antenna Theory, Analysis and Design, 2nd ed. (Wiley, New York, 1997).
  8. P. C. M. Planken and N. C. J. van der Valk are preparing a manuscript called “Measurement and calculation of the near field of a terahertz apertureless scanning optical microscope” for submission to J. Opt. Soc. Am. B.

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