期刊
APPLIED OPTICS
卷 52, 期 3, 页码 330-339出版社
OPTICAL SOC AMER
DOI: 10.1364/AO.52.000330
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资金
- Ministry of Education and Science of Russian Federation [8027]
- Russian Federation Presidential grants for support of the leading scientific schools [NSh-4128.2012.9]
- Young Candidate of Science grant [MK-3912.2012.2]
- Russian Foundation Basic Research grants [12-07-00269, 12-07-31115, 12-07-31117, 13-07-97008]
By decomposing a linearly polarized light field in terms of plane waves, the elliptic intensity distribution across the focal spot is shown to be determined by the E-vector's longitudinal component. Considering that the Poynting vector's projection onto the optical axis (power flux) is independent of the E-vector's longitudinal component, the power flux cross section has a circular form. Using a near-field scanning optical microscope (NSOM) with a small-aperture metal tip, we show that a glass zone plate (ZP) having a focal length of one wavelength focuses a linearly polarized Gaussian beam into a weak ellipse with the Cartesian axis diameters FWHMx = (0.44 +/- 0.02)lambda and FWHMy = (0.52 +/- 0.02)lambda and the (depth of focus) DOF = (0.75 +/- 0.02)lambda, where lambda is the incident wavelength. The comparison of the experimental and simulation results suggests that NSOM with a hollow pyramidal aluminum-coated tip (with 70 degrees apex and 100 nm diameter aperture) measures the transverse intensity, rather than the power flux or the total intensity. The conclusion that the small-aperture metal tip measures the transverse intensity can be inferred from the Bethe-Bouwkamp theory. (C) 2013 Optical Society of America
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