Research On Phase Control Of Light Field For High Efficiency Dielectric Meta-surface

Meta-surface is a kind of two-dimensional electromagnetic material,which can control the amplitude,phase and polarization of light.Compared with bulk metamaterials,the thickness of meta-surface is much smaller than the wavelength of incident light,which is less affected by ohmic loss and easy to process.Therefore,eta-surface has important application prospects in many fields,such as beam control,optical antenna,planar optical devices and so on.It is found that the dielectric meta-surface is an effective way to realize efficient optical transmission.Compared with metal meta-surface,low loss dielectric meta-surface can produce both electric and magnetic responses to the incident light.Huygens meta-surface can be constructed by using the coupling between electric resonance and magnetic resonance,which makes it possible to control the phase effectively while achieving high transmittance.However,most of the current researches focus on the construction of meta-surface structures from single morphology meta-atoms,which has great limitations in the design of degrees of freedom.In this paper,we study the scale effect between the polymorph meta-atoms on the basis of the single morphology meta-surface,and finally achieve the perfect replacement between the different morphology meta-atoms.It provides more possibilities for improving meta-surface efficiency and simplifying machining in the future.In this study,we focus on the construction of meta-atoms and the internal relationship between meta-atoms in super surface design:(1)Based on the motion law of polarization charge in the material,the mechanical regulation process of light matter interaction by the boundary of silicon meta-atom is analyzed.Based on the finite-difference time-domain method,the optical properties of different size meta-atoms are analyzed.According to the characteristics of Huygens meta-surface,by optimizing the size of high refractive index silicon nanostructure,it has both electric dipole resonance and magnetic dipole resonance in a certain frequency range,and a non-reflective Huygens source is obtained.A rectangular meta-atom library is constructed at 1064nm wavelength,and eight meta-atoms with high transmittance and ?/4 phase spacing are selected to control the wavefront.(2)Compared with metal meta-surface,dielectric meta-surface can effectively avoid ohmic loss.However,in the process of constructing the meta-surface,the change of the peripheral structure of the meta-atom will lead to the shift of its optical properties.To solve this problem,five kinds of polymer meta-surface gratings are designed by combining the same meta-atoms into polymers.It is found that the meta-surface grating composed of polymer has higher efficiency.The transmittance of pentamer grating is the highest,which is 85%.For the same grating,the deflection angle increases with the increase of wavelength.For a polymer grating,when the incident wavelength changes 10nm,the deflection angle changes 0.12 ‰.When the wavelength is 1100nm,the deflection effect of the polymer grating is the best,and the deflection angle is 13.248 ‰.In the wavelength range of 1040nm to 1080nm,the designed grating shows good transmittance and diffraction efficiency.The average transmittance is about 80%,and the maximum first-order diffraction efficiency is 92.56%.(3)Aiming at the modulation effect of meta-atom morphology on its optical properties,the similarities and differences of different morphologies of meta-atoms are analyzed in detail,and the specific geometric relationship between different morphologies of meta-atoms at the same period and height is found.A meta-lens composed of rectangular meta-atoms is designed,and then some of the rectangular meta-atoms are replaced by other morphologies of meta-atoms.The final polymorph meta-lens has the same characteristics as the original single morphology meta-lens.(4)Based on the study of the size effect of the polymorph meta-atoms,the spectral characteristics of the polymorph meta-atoms are further analyzed,and the relationship between the resonance wavelength and the size of the meta-atoms is explored.In order to control the singleness of the research object,we designed three kinds of isotropic meta-atoms and established their corresponding meta-atom library.Under wide spectral incidence,the resonant wavelength of isotropic meta-atoms is approximately linear with their size.By fitting calculation,the linear relationship parameter is determined,and the difference between the theoretical resonance wavelength and the actual resonance wavelength is only about 0.5%.