Regulation And Application Of Surface Plasmon Polariton Excitation Based On Zinc Selene/Liquid Crystal Molecular Anchoring

With the further research of photoelectric materials and the maturity of micro-nano optical processing technology,photoelectric functional devices are also developing towards integration,miniaturization,multi-function and active adjustability.The research on the quantized photoelectric effect of monolayer two-dimensional materials such as graphene,molybdenum disulfide and boron nitride has become one of the hot spots.Similarly,the ultrathin charge accumulation layer formed by Metal-Oxidesemiconductor(MOS)at the interface has also attracted extensive attention due to its quasi-two-dimensional characteristics,and has played its own advantages in the field of electrical control.Due to the difference in the electrical properties of materials,an extremely thin layer of charge accumulation is formed at the interface with a very high degree of freedom along the interface.So it is also called two-dimensional electron gas(2DEG).This quasi-two-dimensional material can strongly couple with electromagnetic waves(EM Waves)forming surface plasmon polaritons(SPPs)and significantly increase the density of photon states by confining the electromagnetic field to the very thin region.Thus,it has adopted in a wide range of applications in the fields of optical antennas,optical cloaking,optoelectronic communication,physical imaging,micro lasers and quantum Hall effects.In order to realize the active control of photoelectric devices,the liquid crystal layer is often integrated into devices as a link whose optical properties could be changed by electric field.The active modulation of SPP by using liquid crystal to control the interface performance is very helpful to the research and development of new active optoelectronic devices.In this dessertation,the photoelectric interaction between semiconductor Zn Se thin film and liquid crystal layer at the interface has been deeply studied.The 2DEG aggregation at the interface and electrostatic modification have been analyzed in detail.The surface plasmon polaritons on semiconductor film was excited by phase grating at the interface.The effects on the optical response was analyzed as well.Finally,a periodic structure in plane is designed and analyzed theoretically and numerically,which can integrate the tunable response of localized surface plasmon resonance.Firstly,the surface of Zn Se thin films deposited by electron beam evaporation was analyzed in detail.The unilateral anchoring effect and vertical alignment of 5CB liquid crystal molecules were realized by the surface unsaturated charge.The adsorption of cyan group to Zn Se surface was analyzed by Density Functional Theory.Furthermore,we design a phase modulator which can be controlled by external electric field and realize the rotation of the incident beams polarization.The modulation of the transmittance of nearly 60%.Then,we analyzed the charge transfer and electron transition between Zn Se and5CB molecules at the interface in detail by means of Density Functional Theory.Due to the difference in the electrical properties of the two materials,a charge accumulation layer would be formed at the interface.By using the Thomas-Fermi screening model and the Poisson diffusion equations,the electron density at the interface achieves 4.86×10²⁸m^-3 and decays rapidly at a depth of 1nm.Thus,a layer of electrostatic modification layer is formed at the interface.We use the method of introducing extra charges to calculate the layer's optical properties.The results show that the layer shows a strong metallic property due to the accumulation of charges.Furthermore,we extend the materials to Zn O and Zn S,and theoretically calculate the difference of optical properties of different materials after modification.It is found that the range of metallization exhibits a blue shift with the shortener of lattice constants.Moreover,the materials that can produce metallization have a certain limit.By using the photorefractive grating in the liquid crystal layer and the negative real part of the dielectric constant at the interface,we realize the excitation of the interface SPP.Using the coupling between SPP and incident beams,we analyzed the effects and the adjacent liquid crystal layer in depth,and furthermore,explained the anomalous two dimensional multi orders as well as the giant energy coupling.Finally,we designed a metasurface structure that can form localized surface plasmon resonance with incident lights.The strong intrinsic absorption at 501.4 THz were realized by a set of metal bars,thus achieving electromagnetically induced transparency using plasmonics.The polarization of the incident light is the key to determine the plasmonic oscillation mode.We also introduce a liquid crystal layer to change the polarization state of the incident light,so as to realize the low voltage tuning response.The final plasmonic structure could achieve a modulation depth of more than 85.9%at the wavelength of 932.5 nm.The relationship between the element structure and surface plasmon resonance is also analyzed.This study will provide a new idea for the integration of liquid crystal and semiconductor devices,expand the generalized two-dimensional materials,and also support experimental basis for the study of semiconductor interface modification and tunable SPP.It has wide applications prospect in the research and development of optically controlled active modulators,optical gates and plasmonic applications.