Research On Biosensing Characteristics Based On D-shaped Photonic Crystal Fiber

Photonic crystal fibers are widely used in optical fiber sensing for the characteristics of flexible structure and light-controlling properties.D-shaped PCF is non-circular symmetrical structure,which enlarges the contact area for sensing.And sensing performance is greatly improved due to the strong coupling between core mode and analyte.It is convenient for metal to be coated over D-shaped plane,which overcomes the technical difficulty for being coated in PCF air-holes.Then the stable metallic material enhance the effect of surface plasmon resonance and realize high sensing performance.In this paper,two different models are designed based on D-shaped PCF structure,and refractive index sensing performance was simulated by finite element method.The influence of structural parameters is also studied for improving sensing performance.The results show that both D-shaped sensors exhibit great refractive index sensing performance.The main content of this paper is as follows.1.Firstly,a D-shaped PCF-Bragg grating sensor is designed and the sensing response is achieved by finite element method.The influence of structural parameters on sensing performance,the variation of reflection spectrum and resonance wavelength are studied respectively.The results show that refractive index range is 1.30～1.40,and the resonance wavelength moves to the long-wave direction with the increase of refractive index.And the moving distance also gradually increases,which means the sensitivity is improving.The maximum sensitivity reaches 487 nm/RIU when the refractive index is 1.40.Compared with conventional Bragg grating sensors,the sensitivity of D-shaped PCF-Bragg grating sensor in this paper is greatly improved,which is suitable for refractive index detection and shows good sensing performance.2.Then,a D-shaped PCF-SPR model is designed.The metal grating deposited enhances SPR and the sensing ability for external analyte,thus improving sensing performance.The sensing response is theoretically simulated by finite element method,and the influence of structural parameters on sensing performance,as well as the movement of loss spectrum and resonance wavelength are studied.The results show that refractive index range is 1.30～1.41,and the resonance wavelength is red-shifted with the increase of refractive index.And the loss increases first and then decreases.When the refractive index reaches 1.41,the maximum sensitivity is 11740 nm/RIU and the maximum resolution is 8.52×10-6 RIU.Compared with internal PCF sensors,the D-shaped PCF sensor realizes high sensitivity,high resolution and wide refractive index range.3.Compare the two D-shaped PCF sensors with other similar PCF sensors respectively,and evaluate their sensing performance.The sensitivity of D-shaped PCF-Bragg grating is several times or even tens of times that of conventional grating,which breaks through the application limitation for refractive index detection.The D-shaped PCF-SPR structure can combine high sensitivity and wide refractive index sensing,which has dual advantages over other PCF-SPR structures.