8 January 2015 Optimization of structure parameters of concentric plasmonic lens for 355 nm radially polarized illumination
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We propose and optimize two designs of plasmonic lens structures, concentric grooves with a central hole (CGH) and concentric grooves with a central pillar (CGP), based on a traditional structure of concentric grooves (CG). The numerical investigation based on COMSOL Multiphysics is performed to optimize the three kinds of structures by a 355 nm radially polarized laser illumination. It is found that full-width at half maximum (FWHM) is closely related to the size of the center-position, and the field enhancement effect depends on the resonant wavelength of surface plasmon polaritons, permittivity, film thickness, and groove number. Compared to a FWHM of λ/3 (λ is the wavelength of the laser beam) with the conventional CG type, the combination of localized and extended surface plasmons results in CGP and CGH parameters achieving their optimal value with a much smaller spot size of λ/8 and higher intensity enhancement for a variety of the aspect ratios of central pillar and hole. A focused ion beam was used to fabricate the three type nanostructures with high accuracy. The CGH type with a central hole 20.88 nm in diameter and the CGP type with a central pillar 55.45 nm in diameter have been successfully fabricated approximately to their optimization results.
© 2015 Society of Photo-Optical Instrumentation Engineers (SPIE)
Jiaxin Ji, Yonggang Meng, Jun Zhang, "Optimization of structure parameters of concentric plasmonic lens for 355 nm radially polarized illumination," Journal of Nanophotonics 9(1), 093794 (8 January 2015). https://doi.org/10.1117/1.JNP.9.093794 . Submission:

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