Study On Fabrication And Polarization Selection/ Conversion Properties Of Three-dimensional Micro-nano Structures

Polarization,which refers to the geometrical orientation of oscillating electric fields,is one of the fundamental properties of light.It is also an excellent carrier of information,and is widely used in communication,encryption,imaging,display,remote sensing and other fields.However,the traditional optical systems to control polarization are often large in size and complicated in fabrication process,which cannot meet the development trend of high density on-chip integration and multi-function of devices.In recent years,with the development of micro/nano fabrication technologies and methods,the construction of micro/nano structures with novel polarization characteristics has become a key breakthrough to solve the problem of complex on-chip polarization technology.The design of metasurfaces is one of the significant means to use subwavelength micro/nano structures gaining the optical modulation abilities that beyond natural materials.Polarization modulation metasurfaces can not only greatly reduce the device size,but also achieve unprecedented physical phenomena,and expand the relative applications.The study in this dissertation first focus on separately the metallic and dielectric materials,and metasurfaces with specific polarization selection or conversion characteristics were designed and fabricated by using micronano fabrication techniques with independent intellectual property rights,and their internal physical mechanism,modulation characteristics and potential applications were also studied.In addition,this dissertation also introduces an electron beam direct writing method of three-dimensional micro-nano strain structure,and explores a controllable strain coding and manipulation method for the next generation of quantum information devices for two-dimensional valley polarization materials with polarization selective absorption.Accordingly,the studies in this dissertation are as follows:First,for the metallic plasmonic structures,a series of three dimensional(3D)nano plasmonic structures with specific polarization selection properties are developed by focused ion beam(FIB)induced folding technique.The three-dimensional double flake metasurface and vertical split ring resonators(SRRs)metasurface break through the limits of the dimention for near-field coupling,realizing the polarization selective double tunable Fano resonances and toroidal dipolar,which operate in near-infrared region(NIR)and mid-infrared region(MIR),respectively.By adjusting the 3D spaced symmetry of double flakes,two Fano resonances are generated in the bichromatic absorption of double flakes metasurface,and the sensitivities of each resonance can be independent controlled for refractive index sensing.The measured sensitivity can reach 2703nm/RIU.Besides,the vertical s SRRs metasurface exhibits excellent magnetic confinement and quality factor with the polarization selective absorption for linear polarized light at a 45-degree angle,realizing the toroidal dipole excitation in MIR.These metasurfaces can also be used in other fields including 3D optical antennas,light modulators and logic elements,etc.Secondly,for the dielectric materials,sub-wavelength cross-nanofin(CN)units with various waveplate(WP)functionalities,such as frequency division multiplexing WP,half-WP and quarter-WP are implemented with high efficiency in broadband.Highresolution grayscale image encryption,multi-image storage and rapid polarization detection are demonstrated by encoding the CN pixels into single,double and four channels,respectively.The resolution of stored image reaches 35,219 ppi(pixels per inch),which has fascinating applications in areas such as anticounterfeiting and information.Easy fabrication and multifunction make the CN-shaped WP pixels also a promising candidate in optical device miniaturization,quantum applications and imaging technologies.In addition,for the two-dimensional semiconductor materials,a new technology based on electron beams for stain lithography is introduced.It can implement the complex strain structures on the two-dimensional valley polarization materials.This method can accurately design the shape and range of strains,and it provides a new way for the strain modulation of valley states,which related to light polarization,and design new generation of quantum devices,especially the coherent manipulation of quantum states,quantum information encoding and transmission.