A uniform optical needle focusing microstructure and design method

Abstract

The invention discloses a simple uniform optical needle focusing microstructure and a design method. Two sets of binary amplitude Fresnel zone plate radius sequences corresponding to different focal lengths are composited to block a microstructure center region. According to the constructing process, illumination wavelength and a first focal length are given, and a first set of annule radius sequence {r1, n} is determined; a second focal length is primarily elected to acquire a second set of annule radius sequence {r2, m}; partial sequence segments in {r2, m} are appropriately selected to replace partial sequence segments in {r1, n} to form a new microstructure annule radius sequence; according to each annule transmittance, a center occlusion circle is set first, and alternate coding is carried out according to {1,0} from the radius coordinate of the center occlusion circle to each annule transmittance of the outermost annule radius, wherein the initial annule transmittance is 1; and structural parameters are preferred to realize uniform optical needle intensity field distribution. The design method is suitable for a variety of typical polarized laser beam illumination conditions. The designed microstructure can be applied to laser microfabrication, high resolution microscopic imaging, optical control and other fields.

Description

technical field [0001] The invention belongs to the technical field of micro-nano optics, and in particular relates to a uniform optical needle focusing microstructure and a design method. Background technique [0002] Diffraction of light leads to a complex three-dimensional structure of the focused light field, and modulation of the amplitude, phase, and polarization state of the illumination beam will change the distribution of the focused light field. Since 2008, the problem of light needle focusing (or thin beam focusing) has attracted widespread attention in the scientific community and has become one of the international frontier hot research topics. The uniform fine-light needle focusing field has important scientific research value, and it has important applications in the fields of laser direct writing microlithography, optical data storage, scanning optical nano-microscopy, atomic optics, and optical manipulation. [0003] At present, the fine light needle field ...

AI Technical Summary

Problems solved by technology

Focusing methods of refractive optical systems are represented by multi-annular pupil filtering, vector beam illumination, and refractive lens focusing (see literature H. Wang, L. Shi, B. Lukyanchuk, C. Sheppard, C. T. Chong. Creation of a needle of longitudinally polarized light in vacuum using binaryoptics.Nature Photonics,2008,2:501-505), is a traditional wavefront engineering research method, which has the advantages of clear theory and flexible design. The horizontal width is limited

The focusing method of reflective optical system mainly adopts the combination of pupil filter and parabolic mirror (see literature H.Dehez, A.April, M.Piche. Needles of longitudinally polarized light: guidelines forminimum spot size and tunable axial extent. Optics Express, 2012 ,20:14891-14905), the advantage is that it is easy to realize the limit numerical aperture (NA=1, in air) focusing in theory, the disadvantage is that the focusing light needle field is in the reflection light path, and the difficulty of system implementation depends on the ultra-precision aspheric surface processing method, high cost

The third type of method is based on a planar diffractive optical system, directly using a single planar optical microstructure for focusing (see literature T.Liu, J.Tan, J.Liu, H.Wang.Modulation of a super-Gaussian optical needle by high-NA Fresnel zoneplate.Optics Letters,2013,38:2742-2745), this is a lensless, multi-beam diffraction interference focusing system, the outstanding advantages are simple system, light structure, low cost, flexible design, the main problem is due to Under the conditions of short-wavelength illumination and large numerical aperture concentration of standard Fresnel zone plates, the radial width of the outer annular zone is close to that of a few nanometers to tens of nanometers, which poses very strict requirements on the existing micromachining etching process. requirements

[0004] The above technical problems are the main difficulties faced in the field focusing modulation of the uniform fine light needle

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