Design Of Microstructural Optical Fiber Sensors Based On Surface Plasmon Resonance

Microstructural optical fiber(MOF)sensors based on surface plasmon resonance have been applied in food safety,environmental monitoring,molecular recognition and other sensing fields,and have shown great application value due to its outstanding characters including immunity to interferences,label-free detection,high sensitivity,real-time monitoring and flexible structure design.This kind of sensor has attracted extensive attention by domestic and foreign scientific researchers.This paper focuses on improving the performance of the sensor and proposes three refractive index sensors based on surface plasmon resonance(SPR)by designing the MOF structure.The MOF-SPR sensors are numerically calculated using the full vector finite element method,and the sensing characteristics is analyzed deeply by optimizing the structural parameters.Firstly,a MOF sensor coated with indium tin oxide(ITO)is designed.The structure decreases the difficulty of manufacturing sensor and effectively enhances the sensitivity of the sensor.The performance of the sensor is evaluated by analyzing the peak wavelength of the loss spectrum versus the refractive index of the analyte.The sensor shows excellent peoperty by optimizing the structural parameters such as the thickness of the ITO film,the diameter of the air holes and the distance between the air holes.In the range of 1.26?1.38,the resonant wavelength of the sensor varies from 1380 nm to 2260 nm,the maximum wavelength sensitivity is 35000 nm/RIU.The amplitude sensitivity is 120.73 RIU^-1,and the wavelength and amplitude resolution can reach 2.86×10^-6 RIU and 8.92×10^-6 RIU respectively.Secondly,a six-fold eccentric-core photonic quasi-crystal fiber(PQF)sensor based on surface plasmon resonance is designed using a more diverse quasi-crystal structure.The eccentric structure strengths the SPR phenomenon.As the refractive index range of the analyte is 1.33-1.39,the average wavelength sensitivity of the sensor is 8750 nm/RIU,the maximum wavelength sensitivity and the corresponding refractive index resolution are 21100 nm/RIU and4.74×10^-6 RIU,respectively.The maximum quality factor reaches 106.81RIU^-1.Finally,we designed an eccentric eight-fold photonic quasi-crystal fiber sensor that works in the near-infrared region.The plasma material is partially coated on the outside of the fiber,the method effectively avoids the high-order coupling between the fundamental mode and the SPP mode,reduces the appearance of the sub-peak of the loss spectrum and obtain higher sensitivity.In the refractive index range of 1.380 to 1.413,the average wavelength sensitivity of the sensor is 25458 nm/RIU,the maximum wavelength sensitivity and resolution are 96667nm/RIU and 1.034×10^-6 RIU,and the amplitude sensitivity is 745.2 RIU^-1.