Study On Optical Non-Localities Of Alumina-Based Silver Nanorod Arrays

With the development of science and technology,metamaterials are emerging in the field of electronic countermeasures,electronics,and imaging.Metamaterials can achieve many incredible uses,such as superlens,optical stealth,and photonic circuits.From military to industry,to life and other fields,metamaterials will produce subversive applications.Some materials in metamaterials are metal nanocomposites,and the optical properties of these materials are often affected by the shape,volume fraction,size,and filling medium of the metal nanoparticles.Usually the method to investigate the optical properties of metal nanocomposites is to use the equivalent medium theory to make it equivalent to other homogeneous medium.In order to describe effectively the equivalent homogeneous medium,it is necessary to use the physical quantity that characterizes the interaction between the incident electromagnetic wave and the medium—dielectric constant.Firstly,the local equivalent medium model of alumina-based silver nanorod arrays is established by using MG theory,and the equivalent dielectric constants in the equivalent medium are extracted by the Laplace equation and electromagnetic field boundary continuity conditions.Based on Maxwell's equations,the relationship between the internal wave vector of the equivalent medium and the equivalent dielectric constant is studied,which shows that under certain conditions,the TE wave or TM wave does not produce birefringence when it enters the equivalent medium.A method for calculating equivalent dielectric constant with reflectance and transmittance is proposed.Secondly,an alumina-based silver nanorod array model is established in COMSOL,and we use COMSOL to simulate the transmittance and reflectivity of the alumina-based silver nanorod arrays.The results show that MG theory is more accurate in calculating the equivalent dielectric constant perpendicular to the crystal axis,but less accurate for the equivalent dielectric constant along the crystal axis.After many calculations,it is proved that the L resonance absorption peak will decrease with the increase of the nanorod spacing,and increase with larger incident angle.Finally,the three-wave superposition model is used to non-locally modify the equivalent dielectric constant of the silver nanorod model.The intensity of the L resonance peak calculated by the modified equivalent dielectric constant is only 2 % to 4% in error.Since the three-wave superposition model will bring about a blue shift of L resonance absorption peak,we improve the three-wave superposition model.The improved three-wave superposition model can not only maintain high-precision correction of L resonance intensity,but also solve the blue shift problem caused by three-wave superposition.According to correction factor of the three-wave superposition calculated for the silver nanorod spacing of 8 nm and 9 nm,the variation rule of the three-wave superposition factor with the silver nanorod spacing is analyzed.