An analysis of heterodyne signals in apertureless scanning near-field optical microscopy

Chin Ho Chuang, Yu Lung Lo

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)


This study constructs interference-based model of the apertureless scanning near-field optical microscopy (A-SNOM) heterodyne detection signal which takes account of both the tip enhancement phenomena and the tip reflective background electric field. The analytical model not only provides a meaningful explanation of the image artifacts and errors, but also suggests methods for reducing these effects. It is shown that the detection signal obtained in the heterodyne A-SNOM method has a significantly higher signal-to-background (S/B) ratio than in the homodyne method. It is also shown that the S/B ratio increases as the wavelength of the illuminating light source is increased or the incident angle is reduced. Finally, an inspection reveals two fundamental phenomena which may potentially be exploited to obtain further significant improvements, namely (1) the modulation depth parameter has certain specific values greater than 1; and (2) the AFM tip apparatus using a ramp function.

Original languageEnglish
Pages (from-to)17982-18003
Number of pages22
JournalOptics Express
Issue number22
Publication statusPublished - 2008 Oct 27

All Science Journal Classification (ASJC) codes

  • Atomic and Molecular Physics, and Optics


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