22 October 2010 Numerical calculation of optical probe's polarization characteristics
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The 3D finite difference time domain (FDTD) method was employed to simulate the polarization characteristic of the tapered metal-coated optical fiber probe in the near-field optical. The Scanning Near-field Optic Microscopy (SNOM)'s applications would be extended by controlling the exit light's polarization of the optical fiber probe and analyzing the polarized light which passes through the sample. Uniaxial Perfectly Matched Layers (UPMLs) are used for the Absorbing Boundary Condition, and the Drude model is used to deal with the non-magnetic metal. The light intensity distribution near the optical fiber tip was calculated with linear-polarized incident light. A general relationship between the extinction ration and the probe varying with its relevant parameters has been found by means of making alternations on the aperture diameter(40nm-120nm), the cone angle(20°-90°), the thickness of metal film(50nm-150nm) and material(silver, aluminum) as well as the incident light wavelength(350nm-1000nm) and other parameters. The results show that the above multi parameters have produced a co-effect on the polarization characteristics of the optical fiber probe. Once the other parameters remain constant, the extinction ratio is increasing as the aperture diameter or metal film thickness increases. And the extinction ratio could be decreasing, increasing or fluctuant as the cone angle increases in the different conditions. Al's extinction ration usually is better than Ag's under the same conditions. The wavelength's impact should be linked to the metal's complex permittivity. Therefore, the results have positive significance to the design and application of the high extinction ratio fiber probe.
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Peng Hao, Peng Hao, Zhenxian Zhan, Zhenxian Zhan, Yunliang Wu, Yunliang Wu, Keyi Wang, Keyi Wang, } "Numerical calculation of optical probe's polarization characteristics", Proc. SPIE 7657, 5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Design, Manufacturing, and Testing of Micro- and Nano-Optical Devices and Systems, 76570D (22 October 2010); doi: 10.1117/12.866132; https://doi.org/10.1117/12.866132

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