Research Of Surface Plasmon Resonance Fiber Optic Biosensor

The surface plasmon resonance detection technique is widely used in many fields,such as physics,chemistry and biology.Based on the attenuated total reflection of incident light in the denser medium and optically thinner medium and the principle of wave vector matching,the surface plasmon resonance can detect the small changes of refractive index of the object to be measured.Metals are usually used as the material to excite surface plasmon resonance,but the nature of metal that is easy to oxidize restricts its development.The appearance of graphene has brought the surface plasmon resonance technology into a new era.Graphene is a stable two-dimensional crystal with only the thickness of a single atomic layer.It has excellent photoelectrical properties and affinity to biomolecules.The properties of graphene can be changed by electrical gating or chemical doping,so it has good controllability.In this paper,the structure of surface plasmon resonance fiber optic sensor based on graphene photonic crystal with excellent properties is presented,and the sensitivity and detection accuracy of the designed sensor are discussed by means of transfer matrix method and finite difference time domain method,which provides a new direction for the development of fiber optic sensor.First,the research status of the surface plasmon resonance fiber optic sensor is analyzed.The chemical potential,conductivity and dispersion relation of graphene are described in detail,and the transfer matrix method and finite difference time domain method are briefly introduced.Secondly,based on the graphene instead of the traditional metal as the plasma layer,a new surface plasmon resonance fiber optic biosensor is proposed.graphene supports transverse-magnetic propagating surface plasmon resonance with very high field confinement and very large wave vectors and weakly bounded low-loss transverse electric surface plasmon resonance.The detection of refractive index change is achieved.Transmission matrix method and finite difference time domain method are used to analyze the effects of photonic crystal period,graphene layer number and sensing length on the performance of sensors.The sensor parameters are reasonably configured to improve thesensitivity and accuracy of detection.Based on that,the relationship between refractive index and resonant wavelength is analyzed.An optical fiber sensor based on parallel to two kinds of sensing structures to wide range detection biomolecules is designed,which can change the detection range of sensors by adding PMMA to the graphene layer and change regulation of photonic crystal sensing structure.Therefore,two sensing structures supporting transverse electric surface plasmon resonance without influence of detection range and wavelength are designed.Two kinds of sensing structures are connected in parallel to achieve wide range detection of sensors.Finally,refer to the design principle of optical fiber sensors for the parallel,two kinds of distributed sensor structures are proposed,which are based on the change of the material of photonic crystal and adding different thickness of PMMA to graphene,respectively.At the same time,the chemical potential of graphene is adjusted to make the performance of each sensing structure best.Both of the two sensors have high sensitivity and detection accuracy,and realized the real-time detection of the different positions of the homologous material,or the simultaneous detection of different substances.