Research On SPR-PCF Sensing Enhanced By Metal Nanoparticles

The surface plasmon resonance is widely used in the sensing field because of its advantages of label-free and real-time detection,and high sensitivity.Especially in recent years,the importance of sensing technology in the biomedical field has become increasingly prominent.How to improve the sensing performance has become the focus of research.The combination of surface plasmon resonance technology and local surface plasmon resonance technology is widely used to improve sensing performance.Based on the structural and performance advantages of the photonic crystal fiber,the structure of a photonic crystal fiber sensor based on surface plasmon resonance which is enhanced by metal nanoparticles is proposed in this paper.The project of the structure and the research on the regular pattern of sensing performance has important significance and value.Firstly,a D-type photonic crystal fiber sensing structure based on the surface plasmon resonance is proposed in this paper.The polished surface is coated with metal film,and the air holes of the innermost layer are smaller than the others.The full vector finite element method is used for the numerical study.The effects of structural parameters such as the core position,the thickness of the metal film,the distance from the fiber core to the polishing surface,the air hole spacing,the large air hole diameter,and the small air hole diameter on the sensing performance are discussed respectively.When the core position is located in the center of the fiber,the thickness of the metal film is 45 nm,the distance from the fiber core to the polishing surface is 3.0 μm,the air hole spacing is 2.0 μm,the large air hole diameter is 0.75 times the air hole spacing,and the small air hole diameter is 0.80 times the large air hole diameter,the refractive index sensitivity is 6460 nm/RIU in the refractive index range of 1.36-1.40,the linearity is 0.90,and the full width half maximum is 50 nm.Based on the structure proposed above,metal nanoparticles are modified on the surface of the metal film to improve the sensing performance.A new surface plasmon resonance mode is formed at the contact surface between metal nanoparticles and the metal layer.And the field enhancement effect is also produced.The effects of parameters of the metal nanoparticles such as the metal nanoparticle diameter,the metal nanoparticle relative spacing,and the parameters of the D-type photonic crystal fiber sensing structure proposed above are respectively discussed by the full vector finite element method.When the metal nanoparticle diameter is 12 nm,the metal nanoparticle relative spacing is3.2 times the metal nanoparticle diameter,the thickness of the metal film is 45 nm,the distance from the fiber core to the air hole is 3.0 μm,the air hole spacing is 2.0 μm,the large air hole diameter is0.75 times the air hole spacing,and the small air hole diameter is 0.80 times the large air hole diameter,the refractive index sensitivity is 8100 nm/RIU which increases by about 1.25 times,the linearity is0.91,and the full width half maximum is 58 nm.The structure and the method by which the metal nanoparticles are used to improve the sensing performance of surface plasmon resonance can be applied to biomolecular detection and other fields.