Effect of the Number of Zones in a One-Dimensional Plasmonic Zone Plate Lens: Simulation and Experiment |
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Authors: | Qin Chen |
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Institution: | (1) School of Engineering, University of Glasgow, Rankine Building, Oakfield Avenue, Glasgow, G12 8LT, UK |
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Abstract: | A 1D plasmonic zone plate lens (PZPL) consisting of nano-slits within a metal film introduces a phase delay distribution across
the planar device surface by a modulation of the slit widths and positions to achieve light focusing. Using the finite-difference
time-domain method, the number of zones is found to be a crucial factor for a well-controlled focal length, i.e. at least
three zones are necessary for a PZPL exhibiting a focal length in agreement with the design. This conclusion is confirmed
by confocal scanning optical microscopy on PZPLs patterned in an aluminium film. In addition, subwavelength light focusing
is demonstrated both theoretically and experimentally in a PZPL. A larger PZPL, i.e. more zones, shows a higher resolution.
A full full-width half-maximum of 0.37λ in the focal plane is shown theoretically in a PZPL with seven zones. A comparison between the PZPL and the plasmonic Fresnel
zone plate shows that PZPLs have a higher contrast at the focus. |
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Keywords: | |
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