Research On Omnidirectional Beam Deflector Based On Translation Reconfigurable Meta-surface

The rapid control of electromagnetic beams plays a vital role in communication,target range,medical detection,and other fields.Today,fast beam modulation devices with a large field of view（FOV）have been achieved in microwave and millimeter wave bands.However,in the optical band,both the optical phased arrays,spatial light modulators（SLMs）,and MEMS micro-galvanometers that have been successfully developed have not balanced the modulation rate in the field of view well.On the other hand,metasurface’s high integration,planarization,and high design freedom make metasurface different from traditional devices.Its fabrication process is compatible with today’s mature semiconductor technology,which means metasurface can be used to design high-speed modulation beam deflectors with a large FOV.So,we design a fast metasurface deflector with a large FOV adopting the modulation of translation,and this work contains the following parts:1.The spatial phase distribution function of the translation-reconfigurable metasurface beam deflector is designed theoretically.The wavefront simulation of the phase distribution is carried out by numerical simulation software to verify the feasibility of the design.COSMOL,a commercial software based on FEM,was used to establish the element structure database and perform fine scanning of parameters under 10.6μm incident light.The cylinder with the highest rotation symmetry is selected to design the metasurface array by comparing several different types of structures’amplitude and phase modulation characteristics.The material of the structures and the substrate are monocrystalline silicon;the diameters range from 1.6μm-3.4μm,and the height is 6.5μm.2.Two groups of metasurface beam deflectors are designed to test the field of view and modulation rate.When the elevation angle reaches 65.6°,the needed translation distance,in theory,is 1275μm and 911μm,respectively.This can be used to demonstrate that the elevation angle can be controlled by phase function parameters.Two design schemes of the metasurface array are explored.The metasurface array is fabricated by a semiconductor process,and the parameters are close to the ideal.3.The experimental scheme was designed,and the testing platform was built.The field of view was tested as 131.2°×131.2°under the input of a CO₂ laser with a 10.6μm wavelength.The measured elevation angle and actual displacement are compared with the theoretical calculation.It is found that the theoretical calculation accords with the experimental results,and the error is less than 5%.4.Different frequency squarewave voltage signals are loaded onto the piezoelectric ceramics by the signal generator and voltage driver,making the in-plane translation of the metasurface beam deflector.A mercury telluride detector can be used to test the beam scanning process,and we measured a 6 kHz modulation rate.