Study On Coupling Effect Of Surface Plasmon In Metal Nanostructures And Its Sensing Properties

Surface plasmons(SPs)are collective oscillations of free electrons in metals and have a series of unique optical properties,such as selective absorption and scattering of light,local electromagnetic field enhancement,subwavelength localization of electromagnetic waves,etc.In recent years,with the continuous research on nanostructures,it has been found that plasmonic metal nanostructures have broad applications in biosensing,ultrafast optical information processing,all-optical nanodevices and metamaterials.The paper first introduces the basic concepts,features,phenomena of surface plasmons and the latest research progress in the field of surface plasmons.Then,through the study and exploration of the research progress in this field,the related principles and application techniques of plasmonic sensors based on surface plasmons are systematically introduced.Finally,this paper innovatively proposes two design schemes for plasmonic metal nanostructures with high sensing properties.The content of the paper includes the following two aspects:1.We propose a simple and powerful approach to enhance the LSPRs of metallic nanoparticles by introducing a Fabry-Pérot(FP)cavity for high-quality biosensing.It is shown that by placing an array of metallic nanoparticles at the center of a FP cavity,the strong interactions between LSPRs in metallic nanoparticles and optical cavity modes lead to two ultra-narrowband hybridized modes with a huge electric field enhancement.Based on the ultra-narrowband hybridized modes,a high-quality double-band biosensor with a high RI sensitivity approaching 600 nm/RIU and a FOM exceeding 28 is achieved,which are much higher than what have been reported.These results suggest that such cavity coupling concept could offer new perspectives for achieving ultra-compact efficient biosensors.2.We investigate numerically photonic microcavity-enhanced magnetic plasmon(MP)resonance in metamaterials for high-quality refractive index sensing.The metamaterials are consisting of a top periodic array of U-shaped metallic split-ring resonators(SRRs),a middle dielectric layer,and a bottom metallic backed plate.The top metallic SRRs that are placed at about Bragg distance above the bottom metallic plate constitute a photonic microcavity.Because the MP resonance excited in metallic SRRs is coupled to the photonic microcavity mode supported by the photonic microcavity,the radiative damping of the MP resonance is strongly reduced and consequently its linewidth is decreased dramatically.Benefiting from the narrow linewidth,large modulation depth,and giant magnetic field enhancement at the MP resonance,the cavity-coupled metamaterial sensor has very high sensitivity(S =400 nm/RIU,S* =26/RIU)and figure of merit(FOM =33,FOM* =4215),which suggests that the proposed metamaterials have potential in applications of plasmonic biosensors.