Study Of Circular Polarization Features And Manipulation Based On Tow-dimensional Chiral Superstructure

In this dissertation,features and manipulation of circular-polarization light are studied based on finite element method(FEM).The electromagnetic features of circular-polarization dependent electromagnetic induced transparency(EIT)metastructure are obtained.Moreover,the experimental results reveal the physical principle of the group velocity delay of incident circular-polarized Gaussian light pulses.Firstly,two-dimension(2D)chiral superstructure consisting of two individual planar resonant structures is designed according to the principle of EIT to realize circular-polarization dependent EIT.The simulation results show that EIT emerges only for the incident right-handed circular polarization Gaussian pulses with a group velocity delay of 1.6ns at f=15.3GHz.Furthermore,the superstructure is fabricated by Printed Circuit Board(PCB).Using microwave network analyzer,the transmission spectra are measured.The measured results indicate that the phenomenon is existent.In addition,the effect of the thickness of the dielectric layer and the rotation angle of split ring resonator on the intensity of EIT are studied with the same other geometrical parameters.At last,the 2D superstructure is scaled down to micron-size to study the properties in the terahertz region.Then,the designed 2D superstructure utilizing metal-silicdes are analyzed using FEM.The simulation results show that circular dichroism can be observed in the designed 2D superstructure in the infrared region.When utilizing NiSi,circular dichroism reaches to 0.44 at 2.05?m.The corresponding polarization rotation angle and extinction ratio are 74.7° and 190 respectively.Furthermore,the effect of metal-silicides on circular dichroism,polarization rotation and extinction ratio are studied with the same geometrical parameters.At last,3D chiral superstructure consisting of two individual half helixes are designed according to the principle of electromagnetic induced transparency(EIT)to realized circular-polarization sensitive EIT.The simulation results show that EIT emerges only for the incident left-handed circular polarization Gaussian pulses with a group velocity delay of 17.3ns at f=6.35 GHz.Furthermore,the effect of the distance between two half helixes on the intensity of EIT are studied with the same other geometrical parameters.In a summary,firstly in this dissertation,a kind of 2D chiral superstructure is proposed to realize circular-polarization dependent EIT.Both simulation results and measured results confirm that the phenomenon is existent.Furthermore,the effect of two geometrical parameters on the performance of the device is studied.Secondly,due to the fact that noble metals are used during the fabrications,are incompatible with semiconductor processing.Based on above problem,to detect circular polarization light,the(2D)superstructure utilizing metal-silicdes is proposed in the dissertation.The simulation results show that great properties are observed in the infrared region.At last,in view of the fact that 2D chiral superstructure can realize circular-polarization dependent EIT successfully,the 3D chiral superstructure is proposed in the dissertation.The simulation results show that the 3D chiral superstructure has better properties.