Focusing subwavelength light by using nanoholes in a transparent thin film.
A circle of planar nanoholes in a dielectric thin film can focus light into a sub-half-wavelength spot. The nanostructure with higher rotational symmetry shows better focusing properties. From finite-difference time-domain calculations, we verified such a focusing spot coming from the constructive interference of diffraction beams near the nanoholes. For a 1 microm size lens with eight 200 nm diameter holes, we achieved an optical spot smaller than 250 nm measured at 650 nm wavelength. This nanostructure provides a simple way to massively fabricate a planar lens array with a scale down to the submicrometer level.
Wei
Pei-Kuen
PK
Research Center for Applied Sciences, Academia Sinica, 128, Section 2, Academia Road, Nankang, Taipei 11529, Taiwan. pkwei@gate.sinica.edu.tw
Chang
Wei-Lun
WL
Lee
Kunag-Li
KL
Lin
En-Hong
EH