Research On Fano Resonance And Polarization Conversion Characteristics Of Planar Metamaterials

The new artificial electromagnetic materials(Metamaterials)were proposed theoretically in the 1960s by Veselago,a Soviet physicist,and finally realized after a series of scientific experiments.In the last decade,they received extensive attention due to their strange electromagnetic characteristics different from the conventional natural materials,and became one of the cutting-edge researches in the field of the physics and electromagnetism.In recent years,the Fano resonance in the metamaterials,and the combination of chirality and materials,made the metamaterials combined with many research areas,and became the forefront of interdisciplinary research fields.Chirality,a purely geometrical description to the symmetry of an object,means the structure of the object lack of geometrical symmetry.In 2006,when study the planar chiral metamaterials,N.Zheludev et al found a new electromagnetism effect,named circular conversion dichroism,which is very important,and can lead to the macroscopically asymmetrical transmission.Since the asymmetric Fano resonance was discovered in 1961,it has become one of the most important properties of a quantum system for describing the interaction.The Fano resonance in metamaterial having a steep dispersion characteristic,under certain conditions,is similar to electromagnetically induced transparency phenomenon of quantum systems(electromagnetically-induced transparency,EIT),so that it has widely potential applications,such as sensors,switches,and active devices,etc.Via combining theoretical analysis and experimental verification,this paper studying the Fano resonance and polarization conversion characteristics of planar metamaterials,carried out the relevant theoretical and experimental work,and provided an import reference to the realization of ultra-thin,multi-band,planar metamaterials-based functional polarization devices.Based on a detailed survey in new artificial electromagnetic materials' unique physical characteristics,development history,and domestic and foreign research situation,the main works of this paper are as follows:1.Designed a high-performance all-metal planar metamaterials based functional polari-zation device,which overcame the loss problems of the planar metamaterials with bases.Using numerical simulation and experiment test,this paper studied the inherent principles of Fano resonances in the proposed metamaterials,and discussed the influence of asymmetry and structural parameters of the ring hole on Fano resonances.The experimental test showed that the real test results(shapes of the curves)basically fitted with the theoretical results;2.For the proposed all-metal planar metamaterials,induced chirality will appear for oblique incidence,and then a coupling will appear between the two cross liner polarizations,which are parallel and vertical to the asymmetrical split ring hole,respectively.Strength of the coupling is related to the angle of inclination.When the angle is larger than 50°,a strong coupling would appear between the two cross liner polarizations of the planer metamaterials,and then will cause a very strong chirality,so that a split will arise at the conversion ratio curve of liner polarization,which has not been found to be reported yet.Using numerical simulation and experiment test,this paper studied the conversion characteristics of liner polarization in the proposed metamaterials,and discussed the influence of asymmetry and structural parameters of the ring hole on those conversion characteristics.The experimental test showed that the real test results(shapes of the curves)basically fitted with the theoretical results;3.Studied and discussed the characteristics of the circular polarization of all-metal planar metamaterials with asymmetric holes,and of the single layer planar metamaterials worked at THz band.The results showed that for the all-metal planar metamaterials with asymmetrical split holes,oblique incidence of the circularly polarized waves could be used to realize a circular polarizer.The experimental test showed that the real test results(shapes of the curves)basically fitted with the theoretical results.While for the single layer planar metamaterials worked at THz band,dynamic regulation of intensity of the external pumped source could be used to realize a well switch performance between two resonance peaks.Hopefully,switch devices based on the proposed planar metamaterials could be manufactured,and then a new way to dynamically control circular polarized waves could be provided.