Open AccessAnalysis of focal-shift effect in planar metallic nanoslit lenses
Author(s) -
Yang Gao,
Jianlong Liu,
Xueru Zhang,
Yuxiao Wang,
Song Ye,
Shutian Liu,
Yan Zhang
Publication year - 2012
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.20.001320
Subject(s) - optics , fresnel number , fresnel diffraction , diffraction , focal length , finite difference time domain method , fresnel zone , lens (geology) , physics , fresnel lens , planar , near and far field , cardinal point , fresnel zone antenna , transformation optics , scalar (mathematics) , wavelength , mathematics , metamaterial , geometry , radiation pattern , telecommunications , computer science , computer graphics (images) , antenna (radio) , slot antenna
A theoretical analysis based on scalar diffraction theory about the recently reported focal-shift phenomena in planar metallic nanoslit lenses is presented. Under Fresnel approximation, an axial intensity formula is obtained, which is used to analyze the focal performance in the far field zone of lens. The relative focal shift is totally dependent on the Fresnel number only. The influences of the lens size, preset focal length and incident wavelength can be attributed to the change of Fresnel number. The total phase difference of the lens is approximately equal to the Fresnel number multiplied by π. Numerical simulations performed using finite-difference time-domain (FDTD) and near-far field transformation method are in agreement with the theoretical analysis. Using the theoretical formula assisted by simple numerical method, we provide predictions on the focal shift for the previous literatures.