期刊
JOURNAL OF OPTICS
卷 23, 期 6, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/2040-8986/abf891
关键词
Fresnel zone plate; light focusing; near-field diffraction; solid immersion lens; subdiffraction resolution
类别
资金
- Ministry of Science and Higher Education of the Russian Federation (V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Sciences)
- Tomsk Polytechnic University Competitiveness Enhancement Program, Russia
Binary Fresnel zone plates are commonly used focusing elements in micro- and nano-photonics, with parameters strongly influenced by design factors. Numerical simulations can help identify optimal designs for focusing incident light waves into subdiffraction spots.
Binary Fresnel zone plates (FZP) are among the most commonly used focusing elements of 2D-planar optical circuits in micro- and nano-photonics. When the diameter and focal distance of a FZP are reduced to the wavelength dimensions, the parameters of the focal area experience strong influence by FZP constructive design (material, thickness, depth of zone relief). By means of the numerical simulations, the near-field diffraction of monochromatic optical wave on a wavelength-scale binary phase plate is investigated. We found a range of optimal depths of zone plate grooves etching as well as substrate thicknesses providing the best focusing of the incident circularly polarized optical wave in terms of maximum field intensity and minimum size of the focal spot. A certain improvement of these focus parameters can be achieved by filling the zone grooves with a dielectric having a specific refractive index contrast against the FZP substrate. Additionally, the concept of a super-focus binary phase plate with a solid immersion layer (SIL) in the form of a truncated cone made of the ZP substrate material is proposed. Similar to conventional SIL device, this flat SIL-FZP can focus a circularly polarized optical radiation into a subdiffraction spot with a full-width of the order lambda/2n (n is FZP refraction index).
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