The Study Of Circular Dichroism On Rod Chirality Miro/nano Structure

Chiral structures are widely found in nature,and the basic building blocks of creatures,such as protein and DNA,are also chiral structures.Although the basic physical properties of chiral structures are similar to the properties of enantiomers,the chemical properties are quite different.Therefore,in the realm of biology and chemistry,it is of great significance for researchers to identify the chiral structures.However,the identification of chiral structures often requires the use of circular dichroism(CD).circular dichroism is a property of chiral objects that have differential absorption on left circularly polarized(LCP)incident wave and right circularly polarized(RCP)incident wave.However,these traditional photoelectric detectors are often large,which are not conducive to being integrated to realize miniaturization and multi-function.By using artificial sub-wavelength metastructures,researchers can obtain lots of novel properties and the size of the metastructure is also easy to be integrated,which can overcome the shortcomings of traditional technology.In this thesis,based on previous discussion,we propose two kinds of rod metastructures.We study the circular dichroism under the circularly polarized incident wave by the Finite Difference Time Domain(FDTD)method.The main scientific research results in this thesis are showed as follows:1.We calculate this kind of rod metastructure to study the modification of the circularly polarized incident wave by Jones Matrix.Through the analysis of the calculation results,we find that the length,width and angle of the rod will affect the incident wave.The result can provide a guidance for the design of the rod-shaped chiral structure in the future.2.This thesis proposes a two-layers chiral nano-rod structure.And the effect of circular dichroism and the physical mechanism of it are studied.By the simulation of FDTD Solutions,the result shows the influence of the length,width,and angle of the silver nanorod on the peak of circular dichroism.Through optimizing the geometric parameters,we achieve the largest peak value of circular dichroism.These results can guide the design of practical application of chiral rod structure.3.We propose a giant circular dichroism metastructure with bulk Dirac semimetal(BDS)realized by a three-layer structure which can be easily prepared.FDTD numerical simulation was used to calculate the absorption of LCP and RCP by this metastructure and giant CD value for 0.969 is achieved.By changing the rotation angle of the lower bar for opposite sign,control of the handedness of the metastructure can be achieved.By adjusting the Fermi energy of BDS,continuous change of permittivity of BDS can be obtained and the peak of the CD spectrum is tunable in the range of about 12 ?m.The influence of different incident angles and positional deviation of the lower bar on CD values is also explored.Furthermore,desired results can still be obtained in situations of large angle incidence and positional deviation.The proposed structure has broad prospects in THz biosensor and can provide guidance for the design of similar devices.