Optical Fiber SPR Sensor Based On Au/GST Heterogeneous Membrane Structure And Its Characteristics

Surface Plasmon Resonance（SPR）has proven to be highly promising for biological,chemical,environmental and medical applications since it was discovered.In recent decades,researchers further research on the sensor,and the prism-based SPR sensing platform on which the research is originally conducted has gradually matured.Prism-based SPR sensors are now available in the market.With intensive research in fields such as biochemistry and medicine,the requirements for flexibility,integration and sensitivity of SPR sensors are gradually increasing.Consequently,researchers developed optical fiber SPR sensors based on prism-based SPR sensors.Based on the superiority of optical fibers,optical fiber SPR sensors have the advantages of small size,flexibility,corrosion resistance and low cost.Therefore,such sensors can be applied in complex environments such as in vivo environment,high-voltage areas and large water areas.However,optical fiber SPR sensors are still facing challenges of achieving higher sensitivity and sensing accuracy.Ge₂Sb₂Te₅（GST）is a sulfur alloy.When GST is combined with a gold film to form an Au/GST heterogeneous film structure,the high dielectric constant of GST can cause a significant red shift on the resonance wavelength of SPR sensor.Therefore,the SPR sensitivity and sensing performance are substantially enhanced.In this thesis,an optical fiber SPR sensor based on Au/GST heterogeneous film structure is proposed.The sensor uses a polymer-clad multimode fiber to fabricate a sensing probe.The Au/GST heterogeneous film structure is deposited on the multimode fiber,and the sensitivity and sensing performance of the sensor is enhanced in this way.This structure has the advantages of high sensitivity,high sensing accuracy and simple fabrication.In this thesis,we have done the following work on fabrication and optimization of the optical fiber SPR sensors based on Au/GST heterogeneous film structure:Firstly,the transmission characteristics of light waves,the generation mechanism of surface plasmon waves and the principle of surface plasmon resonance between light waves and metals are described.Verified by formula derivation,the heterogeneous film sensing structure can modulate the sensing wavelength from the visible light band to the infrared band.The principle of the numerical calculation method used in this thesis is expounded.Secondly,a novel optical fiber SPR sensor based on Au/GST heterogeneous film structure is proposed.An experimental device is built to facilitate the testing of sensor characteristics.Finally,several parameters which affect the sensor’s sensing characteristics are discussed separately,including the length of the sensing area,the thickness of the GST film and the thickness of the gold film.By analyzing the sensitivity and figure of merit（FOM）of the sensor,the sensing performance and sensing accuracy of the proposed sensor are quantified respectively.Through comparison and optimization,a sensor based on Au/GST heterogeneous film structure is formed by depositing GST on the gold film.To achieve the best sensing performance,the optimal length of the sensing area is 15 mm,the optimal thickness of the gold film is 50 nm,and the optimal thickness of the GST film is 25 nm.This structure achieves a high sensitivity of 5210 nm/RIU and a FOM of 19.63 RIU^-1.In this thesis,an optical fiber SPR sensor based on Au/GST heterogeneous film structure is proposed.The high dielectric constant of this sensing structure can cause a significant red shift on the resonance wavelength of SPR sensor.The SPR sensitivity and sensing accuracy are significantly improved.The sensor has the advantages of small size,bendability,corrosion resistance and low cost.It has broad application prospects in the fields of physics,biochemistry,environmental monitoring and information processing.