Design And Research Of Optical Devices Based On Metasurface

Metamaterial（metasurface）,an artificial sub-wavelength scale structure,has many peculiar properties which cannot be obtained in traditional materials,providing a new avenue to realize superlens imaging,negative refraction optics,cloaking,etc.By designing the structure of meta-atom and the phase distribution of metasurface,the regulation of electromagnetic waves propagation characteristic can be realized,which has great application values in the field of information communication,beam forming and device integration.In addition,how to realize the flexible control of meta-atom through specific physical methods has become a key issue for the wide application of metasurface.Therefore,exploring high-performance optical devices to realize arbitrary control of electromagnetic waves appears urgent.There are two parts in this paper.The first part focuses on the low information transmission efficiency for some devices in modern wireless communication system.A high-efficiency vortex generation by using transmissive metasurface is proposed to generate vortex beam carrying angular momentum,which can greatly improve the communication capacity.In the second part,a type of switchable metasurfaces designed by employing vanadium dioxide（VO₂）possesses tunable and diversified functionalities through temperature in the terahertz（THz）frequencies.It is expected to be used as temperature sensor and imaging.The main contents of the paper are as follows:First,we proposed a broadband transmissive metasurface to generate vortex beam with l（28）1in a broad band ranging from 8 GHz to 13 GHz.We enhance the working bandwidth by carefully designing the meta-atoms which provide high transmittances along with similar slopes of the phase responses within a large frequency interval.More importantly,the designed vortex beam generator exhibits very high working efficiencies（more than 83%within the whole working band）.In addition,we design a type of switchable metasurfaces by employing vanadium dioxide（VO₂）,which possesses tunable and diversified functionalities in the terahertz（THz）frequencies.The properly designed homogeneous metasurface can be dynamically tuned from a broadband absorber to a reflecting surface due to the insulator-to-metal transition of VO₂.When VO₂ is in its insulating state,the metasurface can efficiently absorb the normally incident THz wave in the frequency range of 0.535-1.3 THz with the average absorption of⁹7.2%.Once the VO₂ is heated up and switched to its fully metallic state,the designed metasurface exhibits broadband and efficient reflection（>80%）in the frequency range from 0.5 to 1.3 THz.We further extend the functionalities by introducing phase-gradients when VO₂ is in its fully metallic state and consequently achieve polarization-insensitive beam-steering and polarization-splitting,while maintaining broadband absorption when VO₂ is in insulating state.Our work provides new ideas for designing broadband,high-efficiency optical device.