Hybrid Plasmonic Nanostructures,Devices And Related Photophysics

Plasmonic nanostructures have attracted extensive research interests because of their unique photophysical properties.Hybrid plasmonic nanostructures,which are based on the coupling between different plasmons or between plasmons and photonic resonance modes,can be used to improve and enrich the photophysics of plasmonic nanostructures,extending the related applications.Plasmonic nanostructure have promising applications in surface-enhanced Raman scattering spectroscopy,chemical and biological sensors,miniaturized plasmonic lasers,solar cells,and high-integration photonic devices.In this thesis,we focus our research on the realization and photophysical investigation on the hybrid plasmonic nanostructures/devices.We summarize our research work in this theis into the following sections:(1)Hybrid plasmons in plano-concave semi-cylindrical nanocavities and applications in optical notch filtering effectPlano-concave semi-cylindrical nanocavity arrays were achieved by combining interference lithography and oblique deposition of a metal shell.Both the theoretical and the experimental investigations confirmed the interaction between localized surface plasmon resonance(LSPR)in the Ag semi-cylindrical nanoshells and surface plasmon polaritons(SPP)in the gold film,inducing a hybrid plasmon.Such a hybridization pcoess led to splitting of the LSPR into bonding and anti-bonding resonance modes that are located at different spectral positions.The anti-bonding resonance mode produces weak radiation into free space and results in a broad-band optical extinction spectrum at its resonance.However,the bonding mode led to strong local field confinement in the plano-concave nanocavites.Narrow-band optical extinction with a amplitude as large as 1.15 OD,corresponding to 97% reduction in the transmission,was achieved in the visible spectrum.Thus,such structures can be used in narrow-band and high-efficiency optical naoch filters.(2)Unidirectional launching of surface plasmonic resonance in an asymmetric plano-concave semi-cylindrical microcavity arraysOn the basis of the symmetric plano-concave semi-cylindrical nanocavities,we introduced breaking structures into the Ag nanoshells and destroyed the symmetry,and consequently exported the confined energy in the nanocavities into a specific direction.For asymmetric plano-concave semi-cylindrical nanocavity arrays,diffractions by the template photoresist dielectric grating and the silver nanoshell arrays produced two sets of SPPs in the underneath gold film,which have different phases.Adjusting this phase shift between the two SPPs,we can achived constructive or destructive interference between them in a defined direction.For the structures with determined parameters,the constructive interference is also determined in a certain space,which appears as a unidirectional propagation of the SPP.This laid the basis for the plasmonic photonic circuits with high integration.(3)Active Fabry-Perot microcavities based on plasmonic feedback and related photophysical characterizationMaking use of the photoreduction of silver nanoparticles,we achieved a plasmonic Fabry-Perot(F-P)microcavity,where silver nanoparticles and a continuous silver film function as the end mirrors,and the sandwiched active organic semiconductor layer as the light-emitting medium.We studied the interaction between localized surface plasmon resonance of the silver nanoparticles and the resonance modes of the F-P microcavity,confirming the optical feedback performance of the plasmonic silver nanoparticles.Fruthermore,we observed a ? shift in the phase difference between the total reflective light by the dielectric film and the scattered light by the ailver nanoparticles.(4)Refractive sensors based on the Rayleigh diffraction anomaly(RA)and its Fano coupling with localized plasmonic resonanceIn a grating coated with aluminum,the TM-polarized light excited simultaneously localized surface plasmon resonance(LSPR)in the aluminum nanolines and the RA in the diffraction by the grating.We revealed a Fano-coupling effect between these two processes and applied them in refractive index sensors.The results told us that the coating with aluminum has effectively reduced the diffraction into the transmission space and enhanced the contrast of the RA in the diffraction into the reflection space.This in turn enhanced the Fano coupling between RA and LSPR.Making use of this kind of Fano coupling,we performed sensor experiments on glucose solutions with different concentrations.High sensitivity was achived for such sensor devices,which is as high as 21 OD/RIU,when it is defined by the ratio between the amplitude of the sensor signal and the corresponding change in the environmental refractive index.