Research On Convergent Optical Field Manipulation Based On Dielectric Metasurface

With the advancement of modern science and technology,the integration of optics,machinery,electronics,computing,and control has become the development direction of instruments and equipment,which requires miniaturization and integration of the optical system.In recent years,metasurfaces have made a series of remarkable progress,which has attracted widespread attention in the field of integrated optics.The metasurface is a two-dimensional planar material composed of periodically arranged optical antennas.Studies on dielectric materials such as silicon,titanium dioxide,and gallium nitride have shown that metasurfaces based on dielectric materials can achieve electromagnetic manipulation while maintaining extremely high efficiency.Therefore,the study of metasurfaces based on dielectric materials is of great significance for miniaturizing optical devices and constructing high-efficiency integrated optical circuits at the micro-nano scale.This dissertation focuses on the convergent light field based on dielectric metasurfaces,and studies the dispersion control method of the convergent light field,the realization of achromatic double focusing,the polarization control of the convergent light field and its application in polarization detection.The main research contents are as follows.Dispersion control of converging light fields based on dielectric metasurfaces.The electromagnetic response of the cross-like optical antenna is studied,and the optical antenna with different propagation phases and different dispersion characteristics is obtained by adjusting its structural parameters.The influence of the arrangement of optical antennas with different dispersion characteristics on the dispersion properties of the converging light field is studied.Based on different arrangements,the electromagnetic responses of focused vortex light generators and metalenses with different dispersion characteristics are simulated,and the influence factors of the focusing ring size of focused vortex light generators and the focal size of metalenses are studied.Based on the linear optical response of materials and the concept of time-bandwidth product,the dispersion limit of convergent light fields based on dielectric metasurfaces is investigated.Studies have shown that the aperture,working waveband and dispersion capability of the metasurface are mutually restricted,and the dispersion capability can be improved by increasing the height of the nanopillars and using materials with higher dielectric constants.Reasearch on achromatic double focusing based on dielectric metasurface.Based on the zero-dispersion control of the converging light field,the realization method of the achromatic double focusing metasurface is studied,and the distribution form of the compensation phase is obtained.Based on the electromagnetic response of the optical antenna,the confinement relationship among the aperture,the distance between the two focal points and the focal length of the achromatic double focusing metasurface is studied.Two arrangement methods of achromatic double focusing metasurfaces are proposed,cross arrangement and partitioned arrangement.The imaging characteristics of achromatic double focusing metasurfaces based on these two methods are studied and compared by simulation.The study shows that the focal size of metasurfaces based on these two methods increases with the increase of the working wavelength.Compared with the metasurface based on the cross arrangement,the focal size of the metasurface based on the partitioned arrangement is smaller.Polarization control and polarization detection of convergent light fields based on dielectric metasurfaces.Two representation methods of polarization state,Jones matrix method and Stokes parameter method,are studied and compared.Based on the manipulation of geometric phase and propagation phase,independent manipulation methods of a set of orthogonal linearly polarized light and a set of orthogonal circularly polarized light are studied,and a polarization-sensitive longitudinal double focusing metasurface is realized.Based on a representation of the Stokes parameter without phase term,the compositional structure of metasurfaces for polarization detection is proposed.The electromagnetic responses of the metasurface to different incident polarization states are obtained by simulation,and the reasons why the polarization states of incident light cannot be directly obtained from the electromagnetic responses of the metasurface are analyzed.With the aid of the instrument matrix,the method to improve the reconstruction precision of the polarization state is studied.The polarization detection accuracy,device working efficiency and robustness of the metasurface in a certain wavelength range are simulated and calculated,which verifies the effectiveness of the design method.