29 August 2005 Mapping of surface refractive-index distribution by reflection SNOM
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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 stepindex 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.
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Ilya P. Radko, Ilya P. Radko, Valentyn S. Volkov, Valentyn S. Volkov, Sergey I. Bozhevolnyi, Sergey I. Bozhevolnyi, Jes Henningsen, Jes Henningsen, Jens Pedersen, Jens Pedersen, } "Mapping of surface refractive-index distribution by reflection SNOM", Proc. SPIE 5858, Nano- and Micro-Metrology, 585807 (29 August 2005); doi: 10.1117/12.612554; https://doi.org/10.1117/12.612554

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