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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 15, Iss. 24 — Nov. 26, 2007
  • pp: 15782–15796

Analytical analysis of modulated signal in apertureless scanning near-field optical microscopy

C. H. Chuang and Y. L. Lo  »View Author Affiliations

Optics Express, Vol. 15, Issue 24, pp. 15782-15796 (2007)

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Eliminating background-scattering effects from the detected signal is crucial in improving the performance of super-high-resolution apertureless scanning near-field optical microscopy (A-SNOM). Using a simple mathematical model of the A-SNOM detected signal, this study explores the respective effects of the phase modulation depth, the wavelength and angle of the incident light, and the amplitude of the tip vibration on the signal contrast and signal intensity. In general, the results show that the background-noise decays as the order of the Bessel function increases and that higher-order harmonic frequencies yield an improved signal contrast. Additionally, it is found that incident light with a longer wavelength improves the signal contrast for a constant order of modulation frequency. The signal contrast can also be improved by reducing the incident angle of the incident light. Finally, it is demonstrated that sample stage scanning yields an improved imaging result. However, tip scanning provides a reasonable low-cost and faster solution in the smaller scan area. The analytical results presented in this study enable a better understanding of the complex detected signal in A-SNOM and provide insights into methods of improving the signal contrast of the A-SNOM measurement signal.

© 2007 Optical Society of America

OCIS Codes
(060.5060) Fiber optics and optical communications : Phase modulation
(180.4243) Microscopy : Near-field microscopy

ToC Category:

Original Manuscript: October 29, 2007
Revised Manuscript: November 8, 2007
Manuscript Accepted: November 8, 2007
Published: November 13, 2007

Virtual Issues
Vol. 2, Iss. 12 Virtual Journal for Biomedical Optics

Y. L. Lo and C. H. Chuang, "Analytical analysis of modulated signal in apertureless scanning near-field optical microscopy," Opt. Express 15, 15782-15796 (2007)

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