Research On Graphene Plasma Optical Fiber Biosensor And Its Application

Surface plasmon resonance（SPR）optical fiber sensing technology is a new method combining plasma optics and optical fiber optics to realize light transmission,coupling,resonance,amplification and detection on micro and nano scales.It can effectively overcome the bottleneck of traditional optical fiber sensing and become a research hotspot of optical fiber sensing technology.As a typical representative of two-dimensional photoelectric materials,graphene is a carbon allotrope with hexagonal lattice arranged by single-layer carbon atoms.It has the characteristics of high strength,zero band gap,large specific surface area and high stability.It can be used as an adsorption material and is easy to be integrated into optical fiber.It has important applications in various fields such as optical communication,optical devices and optical sensing.There are a large number of microstructures in the cross section of photonic crystal fiber,which makes its structural design have great operable space in improving performance.Based on this,from the perspective of structural innovation,this paper systematically studies and designs three graphene PCF-SPR sensors by using finite element method（FEM）,and discusses the excitation and coupling of SPP and its resonant coupling effect with biomolecules.The effects of material properties and geometric parameters on the sensitivity and signal strength of biometrics were studied.Experiments verify the performance of graphene optical fiber sensor.The specific research contents are as follows:Firstly,a D-type graphene-Au PCF sensor is designed,and the refractive index（RI）sensor with high sensitivity from visible light to near infrared band is realized by SPR technology.In the cladding design of the structure,two air holes are missing in the first layer,the air holes in the second layer are arranged in D-shape,and an air hole is designed in the fiber core to make SPR easier to occur.The structural parameters of PCF were analyzed by FEM,and the effects of gold film and graphene on the sensitivity of the sensor were analyzed by SPR technology.The simulation results are as follows:in the RI sensing range of 1.32-1.41,the maximum S_λ of the sensor is 4200nm/RIU,the S_A is 450 RIU^-1,and the refractive index resolution is 2.3×10^-5RIU。Secondly,a biosensor using asymmetric plasma nanoporous graphene to enhance the sensitivity is designed.Using birefringence effect and SPR technology,the sensing detection with high sensitivity and low loss in the visible to near-infrared band is realized.The structure is composed of three annular hexagonal air holes,which is characterized by two large air holes in the horizontal direction of the fiber core.By breaking the orthogonal symmetrical structure,the SPR effect is effectively enhanced.The results show that when the RI is 1.37-1.42 and coated with graphene,the maximum S_lof the sensor is increased to 19200nm/RIU,which is 23.08%higher than that without graphene,and the measurement accuracy is 1.27×10^-5RIU.Finally,graphene oxide long-period fiber grating is designed and combined with cancer embryo detection to verify the application of graphene plasma fiber optic sensor in the field of biosensor,which provides an important experimental basis for the research of graphene biosensor in clinical medicine.The above research provides potential application value for the design of a new generation of high-sensitivity biosensors.