Study On Multi-dimensional Modulation Of Light Based On Metamaterials

Metamaterials are materials engineered to have properties that have not yet been found in nature.It expanded the traditional understanding of the material properties,and improved the degrees of freedom for manipulating light in the micro-nano scales.However,there are still many problems to be solved or further developed in the existing researches.In this paper,we design a variety of metamaterials to effectively control the properties of light field.Meantime,we analyze the mechanism and deep research on the corresponding optical properties.The main contents are as follows:1.We present a broken-nanoring which can realize strongly localized confinement and enhancement for both electric and magnetic fields excited by azimuthally polarized light.Compared with scalar beams,vector beams can better interact with nanostructures,leading to the confinement with higher intensity.By designing the broken-nanoring,two resonant modes are formed by different resonant mechanisms.Meanwhile,the enhancement of the electric and magnetic fields can be further improved by adding a nanoring at the outside of the broken-nanoring to form a composite nanoring,which broaden the applications of the nanostructures.2.Through embedding vanadium dioxide?VO₂?material with phase transition in a traditional plasmonic lens,we realize the dynamical modulation of radially polarized light focusing.The radially polarized light can always be focused beyond the diffraction limit,it has wide and important applications in practice.However,it is difficult to tune the spot location without changing the parameters or materials of nanostructures.We propose a dynamic plasmonic lens whose focusing spot can be tuned between the near and far fields just by decreasing temperature.Fouthmore,the field enhancement and the focal length can be further tuned by adding concentric annular slits and VO₂ nanorings,respectively.3.Generation vector beams at the nanoscale by designing dual-layer metasurfaces.Conventional methords of vector beam generation utilize the spatial light modulator,which controls the light polarization and phase independently.So it is unable to realize vector beams with nano scale since the device is bulky.On the other hand,the general metasurfaces cannot control light polarization and phase with complete 2?range.We present a dual-layer plasmonic metasurface with rectangular nanoapertures to simultaneous control the light polarization and phase.Vector beams with arbitrary spatial variation of phase and linear polarization can be realized.4.Study the realization of controllable optical activity with metasurfaces.In existing methods,the strength of the optical activity is determined by the chirality of the materials,which is difficult to control quantitatively.Here,we investigated an approach to realize and control the optical activity with non-chiral plasmonic metasurfaces.Through judicious design of the structural units,the right and left circularly polarized lights have different phase retardations after transmitting through the metasurfaces,leading to large optical activity.We use crossed-shaped metasurface to prove the theory numerically and experimentally.Moreover,the strength of the optical activity can be easily and accurately tuned by directly adjusting the phase difference.The proposed approach exhibits large optical activity with a high controllable degree of freedom.5.Designing multi-functional metasurfaces,realizing perfect absorption,quarter wave plate and half wave plate at different wavelengths without changing nanostructure.Conventional,one structure performs well in one specific optical phenomenon.It is difficult to realize several functions by utilizing one structure.We design and optimize the parameters of rectangular nanoantennas excited by linearly polarized light,realizing different optical effects at different wavelengths.