Designs Of Hybrid Plasmonic Nanocavity And Plasmonic Optical Modulator Based On Nanowires

The study on metallic nanostructures and properties of Surface Plasmons(SPs)has not only attracted many physics researchers' interest,and also become a hot issue in the current energy science,information science,materials science and other cross-cutting area,due to the rapid development of micro-fabrication technique.In this paper,we study the physical properties of subwavelength transmission and near field local enhancement of SPs.And we design a hybrid plasmonic nanocavity with high quality factor and a plasmonic optical modulator with high modulation depth using numerical calculation methods.Its specific content includes:1.We design a hybrid plasmonic nanocavity based on Distributed Bragg Reflector(DBR),which consists of a high-index GaAs nanowire separated from a silver(Ag)surface possessing shallow periodic gratings by a very thin low-index SiO2 dielectric layer.By using the finite element method,the mode effective refractive indices are calculated,and the grating period of the structure can be determined.Compared with the plasmon laser based on hybrid plasmonic waveguide or the plasmonic Fabry-Perot(FP)nanocavity based on DBRs,this nanocavity is designed to combine the advantages of high-reflection DBRs and hybrid plasmonic waveguide,so it can provide higher quality factor and smaller mode volume.In addition,we also study the influence of the structural parameters on the wavelength of the resonant peak and the quality factor of the nanocavity.Finally,we also demonstrate the utility of the hybrid plasmonic nanocavity to control emission properties of quantum dot and calculate the gain threshold.The nanocavity features advantages of high Purcell factor and low gain threshold,promising a greater potential in deep sub-wavelength lasing applications.2.We report a novel design of graphene-based plasmonic optical modulator,which consists of a Ag nanowire being wrapped with a graphene monolayer.While a thin dielectric spacing layer is used to electrically isolate the Ag nanowire from the graphene monolayer.Because SPs offers unique advantages in supporting sub-diffraction-limited spatial confinement and the strongly enhanced local electric field,so this optical modulator can provide high modulation depth,compared to the modulator using a waveguide structure.The influences of various parameters,such as Ag nanowire radius and incident wavelength,on the modulation depth are studied by the finite element method.In particular,the influence of the thickness of the dielectric layer between the graphene and Ag nanowire on the modulation depth is investigated.Simulation result shows that the optimal modulation depth can be obtained when selecting the optimal thickness of dielectric layer for the specific wavelength of light.We extend this result to telecommunication wavelength of 1.55 ?m and the highest modulation depth of 1.07 dB/?m can be obtained with the optimal dielectric layer thickness of 55 nm by using amorphous silicon as a high-index dielectric spacing layer.