Study On Metasurface Imaging And Holograpy With Multidimensional Light-field Manipulations

Metasurfaces consisting of subwavelength dielectric or metallic antannas are emerging as the most attractive flat optical design which reshape the light field by manipulating the polarization,phase,amplitude and wavelength of the electromagnetic wave.Metasurfaces have ultrathin and ultralight features and can manipulate the light with multi-functionalities in a more flexible way.So far,researchers have developed several phase modulation principles,and domenstrated a varity of applications such as beam transformation,hologram,imaging and other multiplexing functionalities.Metasurfaces not only meet the tendency for miniaturization,lightweight and integration,but also can solve some key problems in traditional lens imaging and holographic imaging,such as limited depth of field,limited information capacity and encryption.It can further spur and enrich the function of the optical system,strengthen and expand its practical applications.Focusing on the metalens imaging and meta-hologram,this thesis provides effective ways through the manipulation of spectral response,polarization and phase of the light to realize non-mechanical tomographic imaging,enriches the functionality of the wave modulation devices,and improves the performances of chiral optical devices.The particular contents include:1.The dispersion properties of the metasurfaces are analyzed.We innovatively proposed to utilize the large dispersion of the metalens to realize the non-mechanical optical zoom and spectral tomographic imaging.Generalized aplanatic phase design for imaging process is proposed,which significantly improves the lateral and longitudinal resolution of imaging.A gallium nitride metalens operating in visible band was designed and fabricated.Its dispersion properties and broadband resolutions were characterized.In the experiment,we demonstrated the non-mechanical spectral zoom,microscopy spectral tomography for 3D slice sample and frog eggs.The comparison with the traditional diffraction lens in terms of signal-to-noise ratio,efficiency and other aspects were performed.This method not only expands the limited depth of field of traditional refraction devices,but also significantly improves the integration and stability of the imaging devices,which has great potential in the field of biological tissue tomography.2.Combining the geometric phase with the propagation phase,the design method for simultaneously controlling the polarization and the phase is proposed.We developed the fabrication technology of silicon nitride metasurfaces working at the wavelength of470 nm.The independent phase manipulation ability of the light with the same polarization state and the orthogonal polarization state was firstly verified experimentally,and polarization-dependent holographic imaging was demonstrated.A metalens and meta-hologram with 1/4 wave plate functionality were constructed and demonstrated with high efficiency by adding the polarization control.Lens focusing and imaging with other arbitrary polarization states on the Poincaré sphere(elliptic polarization states)were designed and verified.It demonstrated the rich polarization and wavefront regulation capabilities of this scheme.This design method can further improve the integration of chiral imaging devices and is expected to be applied to vector holography.3.A phase modulation method based on planar chiral meta-atoms is proposed,and the spin-decoupled meta-holograms are realized.Different from the global effect of the geometric phase,this method is based on the local effect which breaks the mirror symmetry and high order(n>2)rotational symmetry of the plannar meta-atom to realize the phase control of the circularly polarized light.By developing the fabrication of the silicon metasurfaces working under the wavelength of 980 nm,the wavefront control ability of this kind of chiral meta-atoms with a single circular polarized light incidence was verified.Experiment results show the broadband and efficient characteristics.Furthermore,independent holographic images were demonstrated with negligible polarization crosstalk.In addition,combining the chiral meta-atoms with the geometric phase,the same spin-decoupled function were realized with less kinds of meta-atoms.Moreover,the more degrees of freedom and the better performances of the chiral metaatoms were verified through comparison experiments.This method enriches the design principle of metasurfaces and is expected to further improve the performance of chiral optical devices.