Coupled Resonant Modes Of Light And Plasmon In Metal/Dielectric Micro-Nanostructures And Their Modulation Effects On Photoluminescence

Plasmonics has now become a promising research filed,involving many interdisciplinary branches of science and technology frontiers.With rapid development in mirco-nanofabrication and chemical synthesis technologies,it has become possible for people to control the fabrication of as-designed structure units,geometric parameters and their spatial distributions in the nanoscale.In complex plasmonic micro/nano-stuctures,SPRs can couple with other photonic modes in the structures or ajacent cavities to form new resonance modes.By careful designing and optimization of the structure parameters,the coupled modes may demonstrate other novel optical effects and resonance characteristics,e.g.,lower resonance loss,improved local field enhancement,better polarization characteristcis,and wider range in resonance tuning,etc.In this thesis,we designed and fabricated various metal/dielectric-based micro/nano-structures,and studied the low-loss,high quality resonance properties of the resonance modes formed by coupling of plasmonic and photonic modes in the structures.And further we studied influence of the coupled resonance modes on enhancement and regulation of the photoluminesce of light-emitting matters embedded in the resonance structures.Main contents of the thesis are summarized as follows:(1)We design an arrayed Ag NPs structure and demostrate that due to recycling of the scattering loss,the narrowband field enhancement are tunable and its magnitude is even larger than that of single NPs.In addition,we disclose the nonmonotonous dependence of the field enhancement on the tuning wavelength,and demonstrate anisotropy resonance and field enhancement in the arrayed nanostructures.Their dual resonance characteristics may be applied in designing photoluminescence and lasing devices to enhance both the excitation and photon emission efficiencies.(2)Randomly distributed Ag nanoparticles with large area uniformity,adjustable average-particle-size are prepared using vacuum thermal evaporation and annealing process of thin Ag film.On this basis,we fabricate a metallic Fabry-Perot type nanocavity incorporating a layer of randomly-distributed Ag nanoparticles in deep-subwavelength spacings as one end mirror,in which is filled with dielectric PMMA doped with fluorescent molecules of RhB.After inverstigating of the resonance coupling characteristics of the LSP mode of Ag NPs and the 0th mode of F-P cavity,it is observed that the coupled resonance modes have stronger field binding ability and broader tenability.The PL intensity of RhB at the emission peaks were further enhanced for a few to hundreds of times dependent on thickness of the RhB-doped PMMA layer.Besides,the self-absorption effect of dye molecules is promoted equally,as a result,the PL spectra were red-shift in varying degrees.(3)A four-layer waveguide structure with metal gratings is designed and fabricated.The coupling manners between the SP mode and the waveguide mode is analyzed.By optimizing the structure parameters,the DFB resonant structure with high Q factor is obtained,which is in good agreement with the numerical simulation results.When different kinds of dye molecules are added to the low refractive index dielectric layer,the 1st and 2nd order DFB resonance modes are investigated under the pumping of CW DPSS diode laser.In our tests,an edge-emitting ASE with emission peak at 710 nm,(FWHM is 6.1 nm)is observed,and the threshold is less than 170W/cm2.Further more,the dependence on the period is verified.(4)We design and prepare a Multiplexed gratings,which are consisting of multiple harmonic grating features,and show multiplet resonance modes that can be independently adjusted.Based on numerical simulations,we investigated dependences of the resonance modes,field distributions and local field enhancements on structure features of the gratings.In implementation,we elaborated the experimental considerations,and demonstrated the consistency in design and realized features of the structures and their resonance characteristics.This offers flexibility in designing resonance characteristics for various potential applications in nonlinear optics and controlling/enhancement of light-matter interactions.