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Interface Grating Induced Surface Plasmons And Subwavelength Coupling In Semiconductors Coated Electro-optic Materials

Posted on:2019-01-22Degree:DoctorType:Dissertation
Country:ChinaCandidate:T Y XueFull Text:PDF
GTID:1368330566498861Subject:Physics
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With advancing of science and technology and driven by ever growing demand in improving living quality,virtual reality has gradually stepped down from its shrine and entered into our daily life.As an important constituent part of virtual reality,stereoscopic display technology has recently received extensive attention and indepth research in both academia and industry.Having advantages of convenient and anti-fatigue features over traditional binocular parallax stereoscopic display technology,3D holographic display technology has gradually become a hot research topic,and stimulated research efforts globally in searching of video-rate holographic recording materials.This thesis systematically studies holographic grating recording properties of liquid crystal cells with Zn Se aligning layers,and discusses surface plasmon polaritons excitation induced by photorefractive phase grating and electrostatic modification of photoconductive layer and its impact on holographic recording properties induced by subwavelength scale energy coupling.Finally,as another example for 2-dimensional electron gas(2DEG)induced electrostatic modification of semiconductive film,we take ITO-coated iron-doped lithium niobate as polar material to investigate and analyze the corresponding process in the traditional photoconductive layer coated uniaxial crystal material system.Firstly,we chose C60-doped 5CB liquid crystal as host material,using e-beam evaporation method to introduce photoconductive alignment Zn Se layers into traditional liquid crystal(LC)holographic recording system and realized video-rate holographic recording response.We investigated and analyzed the basic properties such as grating recording dynamics,gain coefficients and diffraction efficiency versus applied voltage and grating constant.We also studied the holographic recording dynamics for asymmetric LC cell,and analyzed charge carrier transport process therein.To further improve the response rate,we chose dye PM-597 as alternate sensitizer,studied holographic recording properties of different liquid crystal thicknesses in dye-doped LC system.We found anomalous oscillation of diffraction dynamic in this dye-doped system and abnormal scattering in LC cell with high doping concentrations,and made a preliminary explanation of these phenomena using a physical picture of the excitation of surface plasmon polaritons(SPPs).Secondly,we studied the gain coefficient and anomalous scattering properties of LC systems with different dye doping concentrations.By measuring the photocurrent,the charge accumulation near the interface between LC and photoconductive layer in holographic recording experiment was estimated;Combined charge accumulation with semiconductor electrostatic modification theory,the photorefractive phase grating induced excitation of SPP in holographic recording process and its interaction with photorefractive effect through subwavelength scale energy coupling was analysed,which is behind the anomalous scattering and hexagonal patterns.Also,to ensure the consistency of experiment condition and consistency of measurement,we designed and fabricated wedge-shaped LC cells,studied the gain coefficient versus LC thickness of the cells for C60-doped system,and obtained the highest exponential gain coefficient up to date(10574 cm-1)in liquid crystal system,to the best of our knowledge.Taking the contribution of LC molecular orientation to the electrostatic modification into account,we analyzed the polarization reflective dynamic,and confirmed further the excitation of SPP and its impact on holographic recording induced by subwavelength scale energy coupling.Finally,to check the universality of electrostatic modification in semiconductor casued by polarization induced 2-dimensional electron gas,we coated 150 nm thick indium tin oxide(ITO)film to a wedge shaped iron-doped lithium niobate(Fe:LN)slab,observed large angle scattering,visible band long-range SPPs and strong nearsurface-normal light emission,by comparing with an uncoated LN slab.Taking spontaneous polarization of the LN induced charge accumulation near LN/ITO interface into account,and considering the plasmonic wavelength from transmission spectrum of LN and further estimating of charge screen length,we confirmed the excitation of visible SPPs,analysed their impact on holographic recording,elucidated the unexpected phenomena stated above,and verified the universality of electrostatic modification induced SPP excitation in polarized electro-optical material system.This work will provide a theoretical guidance for exploring fast response and low-voltage operating LC holographic recording system,and offer new insight in developing tunable and low loss surface plasmonic waveguide,which has foreseeable application both in real-time holographic display and integrated optical communications.
Keywords/Search Tags:Surface plasmon polaritons, electrostatic modification, 2-dimensional electron gas, liquid crystal, lithium niobate, holographic recording material
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