Vector Light Field Control Based On Fan-shaped Filte

A cylindrical vector beam,when focused by a high numerical aperture lens,undergoes changes in its polarization state and phase,which lead to alterations in the intensity distribution of the field at the focal point.This unique focusing property makes cylindrical vector beams crucial for numerous applications,such as high-resolution imaging,particle manipulation,Raman spectroscopy,second harmonic generation,particle acceleration,laser cutting,nanolithography,material processing,high-density data storage,all-optical magnetic recording,and spin wave manipulation,among others.Based on vector diffraction theory,the electric field after passing through a high numerical aperture lens can be controlled by modulating the wavefront and interference effects of the beam.Polarization control of the electric field can be achieved by controlling the wavefront shape,which enables the conversion between axial and radial polarization states.Interference effects can also be utilized,for example,to achieve field reconstruction and distribution control by superimposing phases.Therefore,controlling the electric field of a cylindrical vector beam focused by a high numerical aperture lens is not only of great theoretical significance but also of broad practical value.This control method has been successfully applied in multiple fields,including high-resolution microscopy,biomedical imaging,photonics devices,and quantum optics,among others.In the future,this control method is expected to bring about new breakthroughs and developments in more areas.This paper achieves the following research results:1.Two types of single-lens systems with ultra-long transversely polarized optical chains are realized by modulating tightly focused double-ring angularly polarized Laguerre-Gauss beams with multi-area sector filters.One class of optical chains is a dark optical chain consisting of an array of optical black dots interconnected with each other,with an axial length extending up to 28λ and a dark focus volume of about 3.45λ~3 at a transverse half-height full width of 1.8λ.The other type of light chain is a bright light chain composed of isolated bright spot arrays,with an axial length extending to 32λ and a bright focus volume of about 1.18λ~3 at a transverse half-height full width of 0.478λ.Meanwhile,the flexible conversion between the two light chains can be achieved by adjusting the truncation parameters of the incident beam.The length of the optical chain can be further extended by increasing the number of sectors in the multi-area sector filter.This technique has a wide range of promising applications.For example,in the fields of high-resolution imaging and particle manipulation,this ultra-long optical chain can achieve higher spatial resolution and finer particle control.2.A two-loop cosine sector filter is designed by combining phase and amplitude modulation.The filter consists of an inner ring and an outer ring,where the double rings have different numbers of cosine phase pairs.We used this filter to obtain longitudinally polarized optical pins of various lengths in a single-lens system with tightly focused radially polarized Bessel-Gauss beams.The longest light pin obtained had an axial depth of focus of up to 25λ,a transverse half-height full width of 0.39λ,a beam quality of 80%,and an axial uniformity of 95%.The light energy utilization of the sector filter can be maintained above 10% during the formation of the light pin.In addition,we found that the focusing depth of the optical needle is mainly determined by the phase and amplitude modulation parameters of the filter.By increasing the paired cosine phase,the axial depth of focus of the optical needle can be further expanded.The results show that the dualloop cosine sector filter is an effective optical element for generating longitudinally polarized optical needles with different depths of focus and lateral resolutions.3.In the 4π-focusing system,a 3D super-resolved spherical focus with longitudinal polarization can be achieved by modulating the high-order tightly focused hollow Gaussian vector beam by using a specially designed pure phase-type sector filter.The super-resolved focus achieved by this method has high resolution and symmetry,and the3 D radius ratio of its focus can reach 1:1:1,enabling high-resolution imaging of microscopic structures such as biomolecules.In addition,by changing the order of the hollow Gaussian beam,the 3D super-resolution multi-focus distribution can be further realized,and the consistency of its focal points can reach 100%.The ratio of the 3D radius of the multifocal point remains 1:1:1,and this technique can be applied to fields such as multi-beam optical manipulation and imaging.