Study On Super-Resolution Confocal Integrated Lens Based On All-Dielectric Metasurface

Optical microscope has significantly promoted the development of life science,medical and material science etc.,ever since its invention.The imaging resolution of traditional optical devices was limited due to the diffraction of light,which greatly limits the further development of far-field super-resolution microscopy.Optical super-oscillation utilizes propagating waves to generate arbitrary small focusing optical field in the far-field.This provides a new way of breaking the diffraction limit to achieve far-field super-resolution microscopic imaging.In recent years,far-field super-resolution microscopy based on optical super-oscillation illumination device and traditional objective lens detection has been experimentally proved in transmissive confocal systems,but it is difficult to be applied to reflective confocal systems.Therefore,for the demands of far-field,super-resolution,and reflective confocal microscopy,it will be of great scientific significance and application prospect to carry out a study on super-oscillation devices to resolve the contradiction between focus spot size compression and side lobes suppression.In order to solve the contradiction of focal spot compression and side lobe suppression in the existing optical super-oscillator device,this paper proposed a super-resolution confocal integrated lens.According to the principle of optical super-oscillation,the point spread function(PSF)of super-resolution confocal integrated lens was designed and optimized by utilizing vectorial angular spectrum method and particle swarm optimization algorithm.Based on geometric phase meta-atoms,continuous phase(0～2π)modulation for circularly polarized plane wave at wavelength λ=632.8nm was achieved.The focal length and radius of this lens were160λ and 540λ,respectively.Thus,the numerical aperture of this lens can be calculated to be 0.96.The full width at half maximum(FWHM)of lens’ point spread function was0.415λ,smaller than the Abbe diffraction limit 0.521λ(0.5λ/NA).and the sidelobe ratio was 9.92%.As a result,the contradiction between focal spot compression and side lobe suppression is better solved theoretically.In addition,the lens integrates the illumination lens and the collecting lens on the same quartz glass substrate,and it has both the function of super-resolution illumination and super-resolution collection at the same focal length,which is expected to be applied to reflective confocal system to replace traditional diffraction-limited objective lens so as to improve the imaging resolution.Moreover,taking device materials,structural feature size and processing accuracy requirements into consideration,the fabrication technologies of super-resolution confocal integrated lens,such as chemical vapor deposition coating,electron beam lithography and dry etching,were studied.On this basis,the lens was fabricated and characterized by SEM.Finally,by analyzing the existing super-oscillation light field characterization methods,wide field of view and large numerical aperture microscope system was set up to test the performance of this lens.The results show that the FWHM of the point spread function is 0.497λ with a sidelobe ratio of 33.67%.