Premium
Single‐Spot Focusing with Plasmonic Phase Manipulation
Author(s) -
Darak Mayur S.,
Mote Rakesh G.,
Shukla Shobha
Publication year - 2018
Publication title -
annalen der physik
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.009
H-Index - 68
eISSN - 1521-3889
pISSN - 0003-3804
DOI - 10.1002/andp.201800193
Subject(s) - plasmonic lens , optics , plasmon , ray , physics , surface plasmon polariton , lens (geology) , wavelength , diffraction , surface plasmon , near and far field , materials science
The ring structure has an inherent symmetry that can be used to focus light to a single in‐plane spot for near‐field plasmonic applications. However, when excited with a linearly polarized light, it yields split focal spot at the center due to destructive interference of surface plasmon polaritons (SPPs). Here, twin configurations of a slit‐based plasmonic lens for in‐plane focusing of a linearly polarized light are proposed. Lenses are designed based on the ring geometry in order to exploit symmetric nature of the ring structure. Either a metallic or a dielectric semicircular protrusion is introduced in the symmetric ring structure for compensating the phase mismatch between SPPs counter‐propagating from two sides of the ring. The focusing properties of the lenses are analyzed using finite‐difference time‐domain simulations. A single focal spot with full width at half maxima of 0.27 λ 0 and 0.28 λ 0 is obtained for plasmonic lenses with metallic and dielectric protrusions, respectively. Thus the diffraction limit is beaten by focusing the light to a subwavelength region of approximately quarter its wavelength. The lenses have potential applications in nanosensing, nanoimaging, and nanolithography, wherein closely populated focused spots are desired using linearly polarized excitation.