A Design Method for Field Focusing of Hundred-Nanoscale Ultra-fine Light Needle

Abstract

The invention discloses a field focusing design method of a hundred nanometer scale ultra-fine light needle, which belongs to the technical field of nanophotonics focusing and micromachining. The diffraction propagation behavior of the subsequent light field when the metal film ring plate is structured; second, use the equivalent numerical aperture NAeq and the normalized central occlusion factor ε to constrain the lateral scale of the focused beam, and introduce super-Gaussian function constraints in the axial direction to form a super Fine light needle field, thus establishing a nonlinear constrained optimization model; third, use the configured genetic algorithm and fast Hankel transformation algorithm to program and solve the above optimization model; fourth, set the initial parameters for optimization, including structural parameters and algorithm parameters, Execute the optimization algorithm multiple times, and optimize the microstructured metal film ring belt. Based on the present invention, different polarized light beam illuminations and multi-scale microstructure metal film annular strips can be flexibly designed, which can be applied to realize micro-nano lithography, nano-printing, super-resolution microscopic imaging, etc.

Description

technical field [0001] The invention belongs to the technical field of nano-photonics focusing and micro-processing, and in particular relates to a method for designing ultra-fine light needle field focusing at a hundred nanometer scale. Background technique [0002] Since 2008, the field focusing problem of ultra-fine optical needles has attracted widespread attention from the scientific community, and has become one of the international frontier hot research topics. The ultra-fine optical needle field has important engineering application value, such as in the fields of laser direct writing microlithography, optical data storage, scanning optical nano-microscopy, atomic optics, microscopic particle acceleration, optical manipulation and other fields. [0003] At present, the field focusing modulation methods of ultra-fine light needles are mainly divided into three categories, which are based on refractive optical systems, reflective optical systems and diffractive optical...

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Problems solved by technology

The modulation method of the refractive optical system is represented by multi-ring pupil filtering, vector beam modulation, and refractive lens focusing proposed by the Singapore Data Storage Research Institute in 2008 (see literature H.Wang, L.Shi, B.Lukyanchuk, C.Sheppard, C.T.Chong.Creation of a needle of longitudinally polarized light in vacuum using binary optics.Nature Photonics,2008,2:501-505), the research of this kind of method is the most concentrated, the advantage is that the theory is clear and the design is flexible, the disadvantage is the radially polarized vector beam The production system is complicated, the processing requirements of the annular pupil filter are demanding, and the high-end apochromatic microscope objective lens is expensive

The second type of method is based on reflective optical system, which is mainly realized by annular pupil filtering and parabolic mirror focusing (see literature H.Dehez, A.April, M.Piche. Needles of longitudinally polarized light: guidelines for minimum spot size and tunable axial extent. Optics Express, 2012, 20: 14891-14905), the advantage is that it is easy to achieve focusing at the limit numerical aperture (NA=1, in air) in theory, and the disadvantage is that the focused light needle field is on the side of the incident light field, and depends on For ultra-precision aspheric surface processing technology, the surface shape accuracy (PV) processing requirements of metal parabolic mirrors are in the order of λ / 8~λ / 6

[0004] The above problems are the actual difficulties faced by ultra-fine optical needle field modulation at present, especially the existing domestic and foreign reports have not yet found a feasible method that can achieve ultra-fine optical needle field focusing with a lateral scale close to the order of hundreds of nanometers

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