Experiement and simulation on the continuous numerical aperture proposition of sub-wavelength annular aperture
Date Issued
2008
Date
2008
Author(s)
Fang, Chun-Chieh
Abstract
The three-dimensional electromagnetic field dispersion of focused beam is an important issue for optical applications. Since 1959, Richard and Wolf had generated radially polarized (RP) beam by optical mechanism. After that, radial vector beam has attracted a great deal of discussions in recent years. Using sub-wavelength annular aperture (SAA) structure is a brand new method to generate non-diffraction doughnut beam. When the RP beam is focused by SAA structure, the focused RP beam in free space was found to propagate in the J1 Bessel beam format, Both simulation and experimental results showed that sub-wavelength focal spot and long depth of focus were achieved in the above-mentioned combinations. The electric field at focal plane of RP beam can be separated into longitudinal and transverse components. Due to their features and different intensity distribution, there are special phenomena in the electrical field at focus. For example, the intensity ratio of longitudinal and transversal component are found to be related to the numerical aperture (NA) of focal lens used and the focal pattern also depends on NA. For the long depth of focus of SAA structure by RP beam incidence, we proposed that SAA structure is a continuous numerical aperture (NA) optical element. To verify this proposition, we compared the properties of SAA structure with the traditional objective lens illuminated by RP beam.
Subjects
surface plasmon
sub-wavelength structure
Bessel beam
radial polarization
continuous numerical aperture
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-97-R95543015-1.pdf
Size
23.53 KB
Format
Adobe PDF
Checksum
(MD5):96cea2af306773f0248931e4a4ba1158