Investigation Of Nano-Optical Antennas Based On Surface Plasmon Polaritons

With the development of nanotechnology,the demand for miniaturization of antenna size is also increasing.In the light wave band,the wavelength of electromagnetic waves has been as small as nanometers.In traditional antenna theory,due to the existence of the diffraction limit,light waves cannot be efficiently coupled into nanometer-sized devices,and the emergence of optical antennas has solved this problem.Optical antennas can break through the diffraction limit,enhance the interaction of light and matter at the nanoscale,and manipulate the light field,In addition,the optical antenna can also effectively enhance the local field.Because of the existence of these features,optical antennas have received a great deal of attention,and their application research is currently focused on photodetection,sensing,thermal conduction,solar cells,and spectral analysis.This paper focuses on the structure of nano-optical antennas and continues to optimize design.In this paper,the authors studied the effect of ellipsoidal aperture arrays on the characteristics of optical leaky-wave antennas,in addition to,a reconfigurable nano-optical antenna with a radiation pattern was designed and its structure was optimized.This thesis mainly studies from the following two aspects:(1)Based on a four-layer plasmonic structure(silicon-gold-silicon-silicon dioxide),we propose two different kinds of optical leaky wave antennas by constructing different arrays of ellipsoidal holes in the metal layer,they are one-dimensional symmetrical optical leaky wave antenna and two-dimensional symmetrical optical leaky wave antenna.Based on antenna theory and finite element method,some of the physical properties of the antenna were numerically studied,such as return loss,insertion loss,radiation pattern,sidelobe level,directionality,half-power beamwidth,bandwidth,etc.When the operating wavelength of the antenna is 1550 nm,the bandwidths of the two optical leaky wave antennas are 80 THz(including the S+-L+ band),moreover,the directionality of the one-dimensional symmetrical optical leaky wave antenna is larger than the directivity of thetwo-dimensional symmetrical tapered optical leaky wave antenna.In addition,we analyzed the effect of the optical leaky-wave antenna of the filled material,when the antenna ports are filled with air and silicon nitride,both optical leaky-wave antennas exhibit good physical properties,for example,lower return loss and insertion loss.However,for two different fillers,the antenna will have some differences in performance,for example,in a one-dimensional symmetric structure,when silicon nitride is filled at the antenna port,the antenna has less return loss and insertion loss,lower side lobe level,and better directionality.This work is done in the third chapter of the paper.(2)Based on the finite element method,the reconfigurable Nano-optical antenna was studied and analyzed,the Nano-optical antenna structure is composed of three layers of discs.From top to bottom,silicon dioxide—silicon dioxide—silicon are successively arranged,and the gold nanorod array is embedded in the middle layer disc.According to the plasma exciton theory,we studied the far-field radiation and near-field transmission of the Nano-optical antenna in the near-infrared region.The results show that by changing the nanorod array embedding angle ?,not only can the beam orientation of the xoy plane pattern be arbitrarily adjustable,but also the reconstruction of the transmission spectrum can be achieved.In addition,we also studied the effects of other geometric parameters of the nanorod array structure on the transmittance.This work was completed in the fourth chapter of the paper.