Research On Optical Manipulation With Silicon Metasurface

Metasurfaces are novel two-dimensional(2D)specific ordered periodic array,which are composed of sub-wavelength scale particles.The amplitude,phase and polarization of the incident light can be controlled artificially and accurately by the scatter process between the light and nanostructures.Compared with the traditional optical elements,metasurfaces show the outstanding characteristics of compact structure,convenient design,easy processing and low loss,and it has important application value in the generation and manipulation of light and show unique advantages in the integrated photonics and diffractive optical device.In this paper,we hope exploit the advantages of metasurfaces to the full in the manipulation of light.We made detailed research on the design processing of silicon-based metasurfaces,as well as the physical principle and the optical characteristics of metasurface in optical manipulation.we designed a silicon-based metasurface to generate non-diffractive Airy beam,and realize the control of the propagation trajectory of Airy beam;we proposed a novel design method in multifunction metasurfaces,and we designed the birefringent beam splitter and the bifocal metalenses to verify the new methods;we designed a chiral metasurface to realize the rotation of the incident light's polarization direction without changing the ellipticity of the incident light.All the metasurfaces are fabricated by the whole electron beam lithography process,after the fabrication,the metasurfaces were tested in experiment.The main research works and conclusions are shown as following:1.Make research on the physical principle of metasurfaces for realizing optical manipulation.Based on Jones matrix,a variety of metasurfaces design methods for realizing the control of polarization and phase of incident light are presented.The Jones matrix corresponding to the structure's parameters is obtained by numerical simulation of Finite difference time domain.2.By means of geometric phase,a silicon-based metasurface that generates Airy beam efficiently was designed.Based on the angular spectrum of Airy beam,the space propagation trajectory of Airy beam is effectively controlled by adding gradient phase.Based on the principle of geometric phase,a pair of left-polarized Airy beam and right-polarized Airy beam are generated.The polarization,non-diffraction,self-accelerating and self-healing of Airy beam are characterized experimentally.In the visible band of 40nm bandwidth,more than 50%conversion efficiency is obtained.3.A multifunctional metasurface design method of polarization multiplexing is proposed.Under linear-polarized light illumination,the parallel and orthogonal components of the outgput light can be manipulated independently.Based on this methods,the birefringent beam splitter and bifocal metalenses are designed.In experiment,the longitudinal and transverse separation of two focal spots of four metalenses are realized,and the character of two spots are indicated.4.A physical mechanism is proposed to realize large optical rotation with eliminated circular dichroism.The mode response of chiral metasurface is analyzed and the phenomenon of optical rotation is explained.The optical rotation angle is controlled by adjusting the parameters of the chiral metasurface.In the experiment,at wavelength 643nm,a large rotation angle of 54° without circular dichroism was obtained.5.Summarize the processing of silicon-based metasurface.The important fabricated processing for coating,etching,electron beam lithography are summarized,and theirs specific range of technology is given.Based on the fabricated experience of silicon-based metasurface,the important steps for attention and the solutions to some common problems are given.Highlights of the dissertation are as following:1.A pair of spin-separation Airy beam is generated by using the efficient geometry phase mechanism of metasurfaces.The independent propagation of airy beam without interference is realized by adding gradient phase,and the spatial propagation trajectory of Airy beam is also manipulated.In the experiment,at wavelength 650nm,the generation efficiency of Airy beam is very high and can reach 63%.In the visible band of 40nm bandwidth,more than 50%conversion efficiency is obtained.2.The way of eliminating circular dichroism and obtaining large optical rotation is proposed.A novel single layer chiral metasurface is designed.which is easy processing,adjustable and regard left-polarized and right-polarized light as eigen-polarization.In the experiment.at wavelength 643nm.the rotation angle of 54°without circular dichroism was detected.3.A design method of polarization multiplexing is proposed for multifunction metasurface,which can independently control the phase of the parallel and orthogonal components of the incident light.The intensity distribution of the two polarization components can be adjusted by the design of the metasurfaces.