| In recent years,surface plasmons have been playing an important role in the fields of biology,chemistry,materials,medicine and new energy.Especially in the field of biology and medicine,the sensor based on surface plasmons has always been a research hotspot,and how to improve the sensor performance is the research focus in the sensor field.In this thesis,we theoretically studied the coupling between the magnetic surface plasmon resonance and the photonic band gap of the photonic crystal or surface plasmon polaritons.The modulation of the magnetic surface plasmon resonance and the enhancement effect of the magnetic fields were realized,and the high sensitive refractive index sensing performance could be achieved.This thesis mainly includes the following two aspects:1.We systematically study the coupling effect between the magnetic surface plasmon resonance(MPPs)and the photonic band gap in a composite system composed of one-dimensional periodic array of silver nanowire pairs and one-dimensional photonic crystal.A single silver nanowire pair can form MPPs due to the near-field plasmon interaction,while a photonic band gap will be generated in the reflection spectrum of one-dimensional photonic crystal composed of multilayer dielectric films with different refractive index.Our theoretical study shows that MPPs in Ag nanowire pair can be strongly coupled with the photonic band gap when MPPs are close to the photonic band gap,thus forming a hybrid magnetic plasmon mode in the photonic band gap.When this hybrid mode is excited,the magnetic fields in the silver nanowire pair will be greatly enhanced,and its intensity can be 4.3 times that of the nanowire pair array directly placed on the silica substrate.These results suggest that our designed metamaterials have important applications in the fields of magnetic nonlinearity and magnetic sensors.2.The coupling effect between MPPs and surface plasmon polaritons(SPPs)on metal films with periodic nanogrooves is studied in detail.Our theoretical studyshows that when the position of SPPs is close to that of MPPs by adjusting the period of nanogrooves,there will be a strong coupling between MPPs and SPPs,and a very narrow band hybrid mode of magnetic plasmon will be formed in the reflection spectrum.In addition,we also use the coupled model of two oscillators to reveal the physical mechanism of the modes.When the narrow-band hybrid mode is excited,the incident light is almost completely absorbed,so the electromagnetic fields in the nanogrooves will be greatly enhanced.These excellent electromagnetic characteristics are very beneficial for their applications in biosensor.Our study shows that the sensor has very high sensitivity(1500 nm/RIU)and figure of merit(150),which are better than the recently reported plasmonic sensors.These results suggest that our designed metamaterials can find important applications in unlabeled biomedical sensing. |
