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Recent Optical and Photonic Technologies Part 10

Tham khảo tài liệu 'recent optical and photonic technologies part 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 256 Recent Optical and Photonic Technologies field scattering process and two scattering measurements give a consistent result. The measured data is clearly well reconstructed by a simple calculation validating our analysis methods. 2.2 Polarization detection of light scattered off GNPs A general elliptical polarization state of the local electric field at a fixed position r in the x-z plane can be written as Born Wolf 1999 E Local Ex Ez a.e - ua a1 a2 0 6 This field vector rotates at a frequency Ũ along the perimeter of an ellipse. A dipole scattering tip gives a scattered far-field ES X a ELocal where a is the polarizability tensor of the scatterer Eqs. 1 2 . In determining of the polarization states of scattered light we apply the RAE and the Stokes parameter measurement Stokes 1852 . Firstly the polarization state of an arbitrarily shaped light is determined by the RAE method in which a linear polarizer mounted inside the optical path of the scattered light and in front of the detector is rotated by 360 in 10 steps. The detected field intensity passing through a polarizer is then given as cosp 7 where p is the detecting polarizer angle from the x-axis and Ộ.Ạ denotes a time average over many optical cycles. The polar diagram ự p shown in Fig. 4 a recorded by rotating the polarizer in 10 steps allows us to determine the polarization state of the scattered light depicted as a red colored ellipse. The major axis angle of the ellipse corresponds to the detecting polarizer angle at which the measured intensity has its maximum and the major and minor axes lengths are proportional to the square-root of the maximum and minimum intensities respectively. In this way the shape of the polarization ellipse of the scattered field ES is reconstructed. One experimental polar diagram ự pp is explicitly shown in Fig. 4 b a gold nano-particle functionalized tip sits at a selected position and scatters a standing wave created by two counter-propagating evanescent waves on a prism