Analysis On The Polarization Features And The Sensing Applications Of The Metal Micro-Nano Structure Based Perfect Absorber

The Surface Plasmonics is an important component of nanophotonics,and it is also one of the most promising fields of research.Plasmonics cover many disciplines such as chemistry,physics,biology,etc.The isolator components have excellent characteristics that are not available in conventional material devices,such as enhanced absorption,electromagnetically induced transparency and electric localized enhancement field.Using its excellent features can enhance the functionality of electronic devices.In this paper,the finite-difference time-domain method(FDTD)is used to study the improved micro-nanometal thin film absorbers.And the author will use the structure parameters,the polarization direction of the light source to work out the optical response and electric field intensity distribution,exploring the physical mechanism of absorption sensing.The specific contents are as follows:Firstly,The physical mechanism and characteristics of surface plasmon polaritons(excitation mode,dispersion relation,and four feature lengths)are introduced.The related numerical calculation methods are finite difference time domain method and electromagnetic finite element method.Secondly,An improved metal-insulator-metal perfect absorber is designed.It consists of two layers of elliptical nanodisk stacks and a layer of sub-wavelength gold film,which produces perfect absorption when irradiated with vertical light.According to the theoretical calculations,the multiband perfect absorption can be attributed to the plasma cavity mode and dipole plasmon resonance.As the spatial structure of the elliptical structure is broken,the near-perfect absorption state and the near-perfect reflection state can be mutually converted by changing the polarization direction of the excitation source.In addition,with the change of the refractive index of the surrounding liquid sample,the corresponding center wavelength of the reflectance spectrum line will also move accordingly.Thirdly,A near-perfect absorber for an improved metal and dielectric hybrid nanocavity array structure is proposed.It consists of a metal thin film substrate and an alumina cuboid column inserted into a gold cylinder.The simulation results show that:the physical mechanism is due to the plasma chamber mode and dipole plasma resonance.By breaking the symmetry of the structure and changing the polarization angle of the light source,the mutual conversion between the near-perfect absorption state and the near perfect reflection state can also be achieved.The structure's highly sensitive is response to environmental changes in refractive index.The structures mentioned above,their perfect absorption,polarization correlation and sensitive sensing properties are conducive to the development of metal micro-nano devices in the future,and can be applied to biosensors,optical filters,solar energy,and other devices.