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Updated: Jun 24, 2026

A Method to Fabricate Disconnected Silver Nanostructures in 3D
Published on: November 27, 2012
Propagation characteristics of silver and tungsten subwavelength annular aperture generated sub-micron
Tsung-Dar Cheng1, Ding-Zheng Lin, Jyi-Tyan Yeh
1Institute of Applied Mechanics, National Taiwan University, Taipei, Taiwan.
Abstract:
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.
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