Open AccessPropagation characteristics of silver and tungsten subwavelength annular aperture generated sub-micron non-diffraction beams
Author(s) -
Tsung-Dar Cheng,
DingZheng Lin,
Jyi-Tyan Yeh,
Jonq-Min Liu,
ChauShioung Yeh,
ChihKung Lee
Publication year - 2009
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.17.005330
Subject(s) - axicon , optics , diffraction , bessel beam , finite difference time domain method , beam (structure) , aperture (computer memory) , materials science , tungsten , near and far field , numerical aperture , bessel function , depth of focus (tectonics) , physics , wavelength , laser , laser beams , acoustics , metallurgy , paleontology , subduction , biology , tectonics
We examined the optical properties such as propagation modes, focal length, side lobes, etc. of metallic subwavelength annular apertures (SAA) and used finite-difference time-domain (FDTD) simulation to compare our experimental findings. Using two different metals, silver and tungsten, we examined the different optical transmission properties of the two metallic SAA structures. The far-field propagation of the silver SAA structure was found to be a type of quasi-Bessel beam when compared with a quasi-Bessel beam generated by a perfect axicon. The propagation characteristics of these two beams were found to match qualitatively. The far-field transmitted light generated by the silver SAA structure was found to possess a 390 nm sub-micron focal spot with a 24 microm depth of focus, which was much smaller than the focal spot generated by a perfect axicon. We also found that a silver SAA structure can generate a sub-micron quasi- Bessel beam that has a much lower far-field side-lobe when compared to that of non-diffraction beams generated by a tungsten SAA structure.