Research On Microstructure Fiber Biosensor Based On Hybrid Sensing Mechanism

Optical fiber sensing is more and more widely used in the field of biosensing with its advantages of non-destructiveness and immunity from electromagnetic interference.Photonic Crystal Fiber(PCF)has attracted more and more attention due to its flexible structure design,novel transmission characteristics and multi-parameter measurement.As the main component of chromosome,DNA detection plays an important role in gene,proteomics clinical diagnosis,chemical detection,and has become an important topic in the field of life science.Therefore,in this paper different sensing mechanisms are introduced in the PCF structure to achieve DNA concentration detection and eliminate temperature cross-sensitivity at the same time,which has important research significance and application value.Two PCF(ring PCF and non-ring PCF)sensing structures based on surface plasmon resonanc are proposed in this paper.The metal layers of the two sensing structures are both coated outer of the cladding layer.The influences of structure parameters(the thickness of Au film,the spacing of air holes,the diameter of air holes)on the sensing performance are analyzed by the full vector finite element method.The results show that the two sensing structures exhibit obvious SPR effect in a certain refractive index range.When the thickness of Au film is 60nm,the spacing of air holes is2.0?m,and the diameter of air holes is 1.2?m,the sensitivity of the ring PCF sensor structure is up to7300nm/RIU in the range of 1.330-1.370,Figure of Merit(FOM)is 145RIU^-1.When the thickness of Au film is 40nm,the spacing of air holes is 4.0?m,and the diameter of air holes are 1.0?m?1.6?m?2.4?m respectively,the sensitivity of the non-ring PCF sensor structure is up to 15000nm/RIU in the range of 1.330-1.406,FOM is 750RIU^-1.Based on the above discussion,a dual parameter sensing structure based on PCF hybrid sensing mechanism is proposed.In the non-ring PCF sensing structure,the SPR effect between the PCF core and the metal film is used as the sensing mechanism of the concentration of DNA.When the concentration of DNA changes,the peak wavelength of the loss peak changes,so that the change of DNA concentration can be detected indirectly by the shift of peak wavelength in the spectrum.At the same time,a hole in the cladding of the non-ring PCF sensing structure is filled with a temperature-sensitive liquid to form a defect core.The directional coupling effect between PCF fiber core and defect core is used as the temperature sensing mechanism.The influence of structural parameters on temperature sensing is discussed.The results show that when the number of air hole layers is three,the air hole diameter is 1.0?1.6?2.4?m,the air hole spacing is 4.0?m,the thickness of Au film is40nm,the concentration sensitivity is up to 1.36nm/mg/ml in the range of 0.6mg/ml?19.6mg/ml(FOM is 355RIU^-1),the temperature sensitivity is up to-9.5nm/?in the temperature range of-50?50?(FOM is 344.7RIU^-1).The sensing based on SPR and directional coupling effect remain relatively independent.The hybrid mechanism sensing structure in this paper can not only be applied for the detection of DNA concentration,but also can be used for the detection of other biological substances.Thus,the hybrid mechanism sensing structure has potential applications in biosensors,liquid substances detection and other fields.