We propose and experimentally demonstrate annular arrayed-Airy beams (AAABs) carrying vortex arrays by combining multiple beams. The propagation dynamics and abrupt autofocusing property are studied. The focal intensity can be greatly increased by two orders of magnitude by increasing vortex array number. Furthermore, the autofocusing property is also enhanced significantly. This tightly autofocusing property would be advantageous for the generation of high intensity laser, optical manipulation, medical treatments, and nonlinear effects.

Annular arrayed-Airy beams carrying vortex arrays

An analytical model of vector formalism is proposed to investigate the diffraction of high numerical aperture subwavelength circular binary phase Fresnel zone plate (FZP). In the proposed model, the scattering on the FZP's surface, reflection and refraction within groove zones are considered and diffraction fields are calculated using the vector Rayleigh-Sommerfeld integral. The numerical results obtained by the proposed phase thick FZP (TFZP) model show a good agreement with those obtained by the finite-difference time-domain (FDTD) method within the effective extent of etch depth. The optimal etch depths predicted by both methods are approximately equal. The analytical TFZP model is very useful for designing a phase and hybrid amplitude-phase FZP with high-NA and short focal length.

Diffraction theory of high numerical aperture subwavelength circular binary phase Fresnel zone plate.

Trapping two types of particles using a focused partially coherent modified Bessel-Gaussian beam

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Comparative modeling of amplitude and phase zone plates CpaвнiTeльнoe noдeлipoвaнie anплiTyднoй i фaзoвoй зoнныx плacTiнok

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 λ/2n (n is FZP refraction index).

https://google.iopscience.iop.org/article/10.1088/2040-8986/abf891/pdf

Study of focusing parameters of wavelength-scale binary phase Fresnel zone plate

Trapping Rayleigh particles using highly focused higher-order radially polarized beams

The near-field focusing properties of actual hybrid amplitude–phase binary subwavelength Fresnel zone plates (HBSFZPs) are studied theoretically. The analysis based on the exact vector angular spectrum method is done for a radially polarized beam incident on the HBSFZPs. The results show that the near-field subwavelength focusing with a long depth of focus can be obtained using an HBSFZP, which is very useful for near-field subwavelength photolithography and high-resolution microscopy. The position of the actual focus in the near-field focusing HBSFZPs depends on the evanescent wave rather than the propagating wave. The etch depth has an important influence on focusing properties of HBSFZPs.

https://iopscience.iop.org/article/10.1088/2040-8978/16/1/015703/pdf

Analysis of near-field subwavelength focusing of hybrid amplitude-phase Fresnel zone plates under radially polarized illumination

Effect of the shadowing in high-numerical-aperture binary phase Fresnel zone plates

The invention relates to a design method of a high-numerical-aperture short-focal-length step phase position type thick FZP. The step phase position type FZP is equivalent to multiple diffraction screens based on a multi-screen diffraction theory, the diffraction effect in a step phase position type FZP body is considered, a diffraction field of the whole FZP is formed by superposing diffraction fields of multiple equivalent diffraction fields, a vector diffraction theoretical formula is formed, the step phase position type FZP can be designed and diffraction field distribution can be analyzed according to a vector diffraction theory. By adopting the design method, a computing result can be basically consistent to a time domain finite difference simulated result, and the high-numerical-aperture short-focal-length step phase position type thick FZP can be simply and effectively designed.

Design method of high-numerical-aperture short-focal-length step phase position type thick FZP

We report a novel method for enhancing near-field nanophotolithography using negative-refractive-index slabs. In our method, a negative-refractive-index-metal film (NIF) is attached to the plane surface of an aplanatic solid immersion lens (SIL), and the polymer layer is coated on the negative-refractive-index film. The intensity of the transmitted light is enhanced by the surface plasmon polaritons excited in the NIF-polymer composite layer. The numerical results based on the vector diffraction theory show that under the illumination of the SIL-NIF-polymer composite by a sharp focused radially polarized beam, the composite configuration under investigation can substantially increase the spot intensity, suppress the spot expansion along the distance from the interface, and improve the depth of focus, in comparison with conventional focusing systems using bare SILs. In the case where a photoresist film is placed near the composite configuration, a subtle deep-etching pattern with high resolution can be achieved.

Youyi Zhuang

Papers

Trapping Rayleigh particles using highly focused higher-order radially polarized beams

Analysis of near-field subwavelength focusing of hybrid amplitude-phase Fresnel zone plates under radially polarized illumination

Effect of the shadowing in high-numerical-aperture binary phase Fresnel zone plates

Design method of high-numerical-aperture short-focal-length step phase position type thick FZP

Enhancing near-field photolithography by surface plasmon polaritons excited from negative-refractive-index nanofilms