Research On On Randomly Distributed Antireflection Micro-Nano Structured Metasurfaces

For anti-reflection micro-nano structures,the morphology,distribution,form and diameter of interface structures,as well as the properties,characteristics,configuration and composition of artificial materials are obviously the most important factors for reducing light reflection and improving light transmittance and absorptivity.Over the past few decades,a large number of artificial antireflective metasurfacements with arrays of micro and nano structures have been prepared,inspired by natural organisms with complex antireflective architectures,to improve the optical properties of the interface between air and substrate materials.By taking advantage of these excellent properties,antireflective micro-nano structure metasurface has been widely used in solar cells,photodetectors,optical systems and other fields.Compared with the periodic uniform distribution structure,the randomly distributed micro-nano structure has an outstanding advantage,which can effectively reduce the influence of the periodic structure on the performance of the optical system.In addition,due to the asymmetry of the randomly distributed micro-nano structure,the sensitivity of incident light angle and polarization can be effectively reduced.In view of this advantage,this thesis starts from the modeling of random micro and nano structures,studies the influence of random distributed micro and nano structures on metasurface properties,and achieves the purpose of reducing the diffraction effect of optical system,and carries out the following work:1.In this thesis,random variable deviation is introduced into the periodic structure to establish a simulation model of random distributed micro-nano structure.The mechanism of action and performance of metasurface affected by random diameter deviation,random height deviation and random position deviation are analyzed,and the correctness of model establishment is verified.It provides a good foundation for the follow-up research.2.Aiming at the low absorption efficiency of anti-reflection micro-nano structure,a mushroom micro-nano structure was designed,which was composed of semi-spherical Ag nanoparticles and silicon-based waist structure.The electric field distribution of single waist anti-reflection structure,single Ag nanoparticles and mushroom structure was simulated,and the mechanism of light absorption under the three structures was analyzed.Verify that mushroom type structure has stronger absorption capacity.The mushroom-shaped silicon metasurface showed a wide spectrum and wide Angle superabsorption,and the average absorption rate reached 98.7% in the spectral range of400-2000 nm under 45° incident light irradiation.In addition,it also shows good electrical performance,improving the spectral responsiveness and detection sensitivity,the maximum responsiveness is increased by 4 times,and the dark current is reduced by 3 orders of magnitude.3.In order to reduce the influence of the diffraction effect of optical system components,the silicon dioxide metasurface with random distribution parabolic cone structure is designed and prepared.Due to the asymmetry of the random distribution structure,the metasurface can also effectively reduce the sensitivity of incident light Angle and polarization,and achieve the high transmittance characteristics of optical system components with wide spectrum and wide Angle.At a large Angle(0°-60°)incidence,the average transmittance reaches 98% in the measured spectral range.Moreover,it is self-cleaning,and the maximum hydrophobic Angle is 160.3°.4.The sample of randomly distributed structure is put into the optical telescopic system and its MTF curve is tested.It is proved that the introduction of random distributed structure will not affect the imaging performance of the optical system.5.By combining the random parabolic cone structure with the microlens with radial gradient structure,the focal length of the composite random microlens is reduced from 17μm to 15 μm,the focal spot center intensity is increased by 7.3%,and the transmission is increased by 3%.The high focus and short focal length of the microlens converging spot are achieved,which is of great significance for the imaging and detection system.