Near-field mapping of surface refractive-index distributions

✍ Scribed by I.P. Radko; V.S. Volkov; S.I. Bozhevolnyi; J. Henningsen; J. Pedersen

• Book ID: 102443950
• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 248 KB
• Volume: 2
• Category: Article
• ISSN: 1612-2011
• DOI: 10.1002/lapl.200510023

✦ Synopsis

Scanning near-field optical microscopy (SNOM) in
reflection is employed for high-resolution mapping of surface
refractive-index distributions. Two different single-mode optical
fibers with step-index profiles are characterized using a
reflection SNOM setup, in which cross-polarized detection is
employed to increase the contrast in optical images and, thereby,
the method sensitivity. The SNOM images exhibit a clear
ring-shaped structure associated with the fiber step-index
profile, indicating that surface refractive-index variations being
smaller than 10^-2^ can be detected. It is found that the
quantitative interpretation of SNOM images requires accurate
characterization of a fiber tip used, because the detected optical
signal is a result of interference between the optical fields
reflected by the sample surface and by the fiber tip itself. The
possibilities and limitations of this experimental technique are
discussed.