A new plasmonic nanolens that can be tuned by varying the circular structure into an elliptical annulus and the aspect ratio from 1 to 0.1 and 1 to 2, respectively, is proposed. Using the rigorous finite-difference and time-domain algorithm, we find that when the aspect ratio ranges from 1 to 0.1, a good linear relationship exists between the aspect ratio and focusing spot size at the full-width at half-maximum in the x- and y-directions, respectively. The corresponding calculated FWHM ranges from 96 × 126 (nm) to 15 \times 52 (nm) (Full Width at Half Maximum).
© 2014 Chinese Optics Letters
(000.4430) General : Numerical approximation and analysis
(240.6680) Optics at surfaces : Surface plasmons
(350.5730) Other areas of optics : Resolution
(310.6628) Thin films : Subwavelength structures, nanostructures
Optics at Surfaces
Shuiyan Cao, Weixing Yu, Cheng Wang, and Yongqi Fu, "Tuning the focusing spot of plasmonic nanolens by aspect ratio under linear polarization," Chin. Opt. Lett. 12, 012401- (2014)