Numerical Study of a Novel Bi-focal Metallic Fresnel Zone Plate Having Shallow Depth-of-field Characteristics

We propose a novel bi-focal metallic Fresnel zone plate (MFZP) with shallow depth-of-field (DOF) characteristics. We design the specific annular slit patterns, exploiting the phase-selection-rule method along with the particle swarm optimization algorithm, which we have recently proposed. We numeric...

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Bibliographic Details
Published in:Current optics and photonics 2018, 2(2), , pp.147-152
Main Authors: Kim, Jinseob, Kim, Juhwan, Na, Jeongkyun, Jeong, Yoonchan
Format: Article
Language:English
Subjects:
Algorithms
Depth of field
Electron beams
Fresnel zones
Ion beams
Laser beams
Laser machining
Micromachining
Optical trapping
Particle swarm optimization
Sidelobe reduction
Sidelobes
Zone plates
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Summary:We propose a novel bi-focal metallic Fresnel zone plate (MFZP) with shallow depth-of-field (DOF) characteristics. We design the specific annular slit patterns, exploiting the phase-selection-rule method along with the particle swarm optimization algorithm, which we have recently proposed. We numerically investigate the novel characteristics of the bi-focal MFZP in comparison with those of another bi-focal MFZP having equivalent functionality but designed by the conventional multi-zone method. We verify that whilst both bi-focal MFZPs can produce dual focal spots at 15 µm and 25 µm away from the MFZP plane, the former exhibits characteristics superior to those of the latter from the viewpoint of axial resolution, including the axial side lobe suppression and axial DOF shallowness. We expect the proposed bi-focal MFZP can readily be fabricated with electron-beam evaporation and focused-ion-beam processes and further be exploited for various applications, such as laser micro-machining, optical trapping, biochemical sensing, confocal sensing, etc.
ISSN:2508-7266
2508-7274
DOI:10.3807/COPP.2018.2.2.147