Research On The Principle Of Color Display And Polarization-multiplexed Techniques With Plasmonic Nanostructures

Surface plasmons are collective free electron oscillations that exist at the interface between metal and dielectric materials.When light of select wavelength strikes a metallic nanoparticle,the electric field of the light drives metal's free electrons to resonantly oscillate inside the particle,leading to unprecedent phenomenon such as extraordinary transmission,prefect light absorption,subdiffraction focusing and structural colors.Recently,with the development of the micro-nano fabrication technologies and characterization methods,principle of the subwavelength plasmonic nanodevice aroused researchers' huge interests.In this thesis,we mainly focused on the principle of color display and polarization-multiplexed techniques with plasmonic nanostructures,which provided valuable reference for the real-life application of the polarization-multiplexed plasmonic color device.This thesis includes the following main work and conclusions:(1)Considering the problems of diffraction-limited focusing spot and short focal length in the conventional lens,we proposed a near-field plate based on amplitude-modulated metasurface,which relaxs the limitation between the spot size and working distance.Actually,the spot size can be theoretically decreased to infinitely small with the radiationless electromagnetic interference and back-propagation method.(2)Considering the problems of low absorption efficiency and bulk-size device;we investigated different plasmonic resonant modes excited by two types of subwavelength metamaterials including metal-dielectric and metal-dielectric-metal constructions.Based on this,various optical devices with different functions are proposed and optimized,such as broadband electro-magnetic wave absorbers covering visible and near infrared regions,select thermal radiatiors and subdiffraction near-field plate lens.Compared with conventional optical elements,these plasmonic nano-optic devices not only exhibit good optical reponse,but also can be easily integrated to optical system due to the features that nanoscale,high-efficiency and stable performances.(3)Considering the problem of color generation is limited by the nanoantenna's dimensions and resonant modes,we design a gap-plasmon based structural color device,realizing full color display and polarization-tunable function.Strongly confined electromagnetic mode and subwavelength unitcell lead to perfect absorption and high incident angle tolerance.(4)Considering the problem of low saturation of plasmonic colors,a novel mechanism,photon spin restoration,is proposed based on ultra-shallow silver grating.We fabricate the sample by interference lithography and experimentally observe full RGB color display,tunable color logo imaging and chromatic sensing.Unique combination of high efficiency,high-saturation output colors,tunable chromatic display,ultrathin structure,and friendly for fabrication makes this design a substantially forward step to bridge the gap between the theoretical investigation and real-life applications.(5)Considering the problem of limited tuning region,large pixel size and “cross-talk” effect in polarization tunable colors.We design and experimentally demonstrate a surface-relief aluminium metasurface that enables advanced optical data storage,based on plasmonic color generation.Excitation of localized surface plasmons encodes discrete combinations of incident and reflected polarized light into diverse colors,broadly increasing the information capacity that can be stored in an individual nanopixel.The combination of diverse colors and high spatial resolution(~34,000 d.p.i.)allows for the metasurface to create robust,highly discernible color code sequences.This configuration shows substantial promise for high-capacity data storage.Furthermore,we propose an advanced parallel read-out system to realize rapid data acquisition unattainable with conventional optical data storage techniques.Moreover,with specific designs,such metasurface can realise advanced steganography using dynamic “kaleidoscopic” images with abated “cross-talk” effect,as well as an alphabet-based information encryption system.Our approach lays the groundwork for multifunctional plasmonic metasurfaces that can be used to address existing challenges in information technology.