Study On Unit Structure Of Metasurface And Design Of A Related Device

Traditional optical devices are challenging to meet the requirements of lightweight,high integration and miniaturization of new optical systems.In recent years,based on the interaction of light and matter,the use of micro-nano structures to control light waves to achieve focusing and imaging has become the global.The cutting-edge technology that is racing to develop provides a new way of thinking to solve the problems of traditional optical systems.Metasurfaces flexibly adjust the phase,amplitude,and polarization of electromagnetic waves based on generalized Niel's law,so that the light waves have abnormal refraction.Metasurface breaks through the traditional optical phase control principle.The novel light wave control method and unique advantages show a wide range of application prospects in various fields,providing the possibility for high-precision,small-sized advanced optical devices.It has been widely used in the fields of focus imaging,stealth materials,sensors,optical system integration,and lidar.In this paper,through the combination of the optical simulation analysis and experiments,the structure of the metalens at the near-infrared operating wavelength is studied using the finite-difference time-domain method,and the influence of the radius,height,and period value of the cell structure on the phase delay distribution is studied.And the influence of different parameters on the coupling effect and the performance of the metalens,and the processing and performance testing of the metalens are completed.The main research contents include the following three parts:(1)Research on near-infrared polarization-independent metalenses.The silicon cylindrical unit structure was established by the finite-difference time-domain software FDTD.The light field distribution under different parameters was scanned at a fixed point by simulation,and the phase delay distribution laws under different silicon column radius,height,and unit structure period were obtained.Within a certain range,the phase delay increases with increasing height and radius,and the transmittance increases with decreasing unit structure period.The final optimized parameter radius is 100 ? 200 nm,height is 900 nm,and period is 500 nm.Finally,a metalens with focusing function is constructed according to the wavefront reconstruction equation with a focal length of 20?m.(2)Research on the super-lens performance of adjacent unit structured light field.A physical model of the two unit structures was established using FDTD,and the electric field distributions of the height changes of the unit structures and the distances between adjacent unit structures were simulated.It is found that the distance between adjacent element structures is a key factor affecting the coupling effect.Under the condition of a certain height and period,the distance can be changed by changing the radius of the unit structure.As the distance decreases,the effect of the coupling effect on the phase becomes more obvious,and the phase failure points increase,resulting in the inaccurate phase control..In addition,try to avoid the area of the phase failure point,and use the optimized optimal parameter values to construct the super lens.Simulation simulations have found that the super lens considering the coupling effect has greatly improved the transmittance and focal shift phenomenon compared with the former.Obviously improved.(3)Processing and performance testing of super lenses.Aiming at the optimally designed super lens,using a combination of electron beam lithography and Lift-off process,a circular super lens with a radius of 10 ?m was successfully processed.The optical system test platform was built to test the performance of the super lens,and it was found that the super lens can achieve the focusing function under the action of a 1310 nm laser source.