Study On The Control Of Light Field Based On Optical Metasurface

Optical metasurface is a two-dimensional artificial material composed of sub-wavelength structural units,which can effectively control the polarization,amplitude,phase and other properties of the electromagnetic field.With the deepening of research on super-surface structures,optical metasurface with new functional structural units have been continuously proposed.Optical metasurface based on surface Plasmons,which can regulate light field on the sub-wavelength scale,has a great potential application in the manipulation of light field.In this paper,we mainly study the application of optical metasurface in light field manipulation,and the following research works are carried out:(1)The optical metasurface combined with a small hole and concentric semicircular grooves obtains a bunched surface Plasmon beam,which can propagate forward a few microns along the symmetry axis of the concentric semicircular grooves with a small divergence angle.The semicircular groove plays a reflection effect on the surface Plasmon like a concave mirror,interferes on the axis of symmetry,and forms an enhanced or weakened surface Plasmon field according to the difference in phase difference.Using the finite element method to calculate the surface Plasmon field distribution,the effects of the polarization state of the excitation light and the excitation source position on the surface Plasmon field distribution and transmission length were analyzed,and the full width at half maximum with the excitation source position was also given.By adjusting the polarization,source position,wavelength and other parameters of the excitation light,surface Plasmons with strong bunching and small divergence angles can be obtained,which is of great significance to the improvement of integrated optics and the expansion of super lens applications.(2)An optical metasurface based on spiral grooves is designed to detect the spin angular momentum of photons.The spin angular momentum of the incident light is coupled with the spiral groove structure.The intensity of the interference field of the excited surface plasmon in the central region of the spiral groove is related to the spin angular momentum of the incident light.The finite element method is used to calculate the field distribution of the surface Plasmon excited by the incident light with different spin angular momentum.The extinction ratio is used to analyze the ability of spiral groove structure to detect the spin angular momentum of incident light.The extinction ratio is given under different incident light and different spiral groove structure parameters.The optimal working wavelength and spiral groove structure parameters of spiral groove structure are analyzed.The research on the detection of spin angular momentum of photons based on the hypersurface structure of spiral grooves provides a new way for information processing in integrated optics,which is of great significance for its development.(3)A method for preparing optical vortex beam with multi-order of orbital angular momentum(OAM)superposition is proposed.By designing an optical metasurface based on waveguide holographic gratings and the Fourier transform principle,a reconfigurable vortex beam generator is realized.By controlling the phase and amplitude of incident light in the waveguides,the OAM of the generated vortex beam can be manipulated.The vortex beam generator with nine fan-shaped waveguides gratings can realize the switching of the OAM order from-2nd to +2nd and maintain high fidelity.This research can expand the application scope of optical OAM and play an important role in the quantum information processing.