Research On Optical Fiber SPR Sensor With Dual Parameters Measurement Based On Ge₂Sb₂Te₅

Surface plasmon resonance（SPR）technology has the advantages of no marking,real time and strong stability.It helps greatly improve sensor sensitivity.In the field of biochemistry,the molecules usually need to be detected at low concentrations.Therefore,designing the sensors with higher accuracy has profound meaning.With the development of aerospace,biochemistry and ocean exploration,the miniaturization and integration of sensors become the focus.At present,developing the sensor of high precision,low cost and high integration has become the main research direction.As light travels through the fiber,the loss is extremely low.Because the optical fiber SPR sensor has the advantages of electrical insulation,anti-electromagnetic interference,high measurement accuracy,small size and long distance monitoring,we propose and demonstrate an ultrahigh-sensitivity optical fiber temperature sensor with a Ge₂Sb₂Te₅modified gold film.Finally,we propose and demonstrate the fiber optic SPR sensor based on Ge₂Sb₂Te₅ and polydimethylsiloxane（PDMS）for simultaneous measurement of temperature and refractive index（RI）.The sensor effectively avoids crosstalk.The innovative achievements of this thesis are as follows:We propose and demonstrate an optical fiber SPR temperature sensor based on Ge₂Sb₂Te₅.The experience uses plastic-clad silica fiber.Gold film and Ge₂Sb₂Te₅ film are coated on the surface of optical fiber.The fiber sample is encapsulated in cyclohexane to achieve temperature sensing.Ge₂Sb₂Te₅ has high dielectric constant.When Ge₂Sb₂Te₅ is coated on the surface of the gold film,the resonant wavelength is red-shifted.With the increase of resonance wavelength,the penetration depth of evanescent wave increases.Therefore,the sensor sensitivity is greatly improved.In addition,when the fiber is exposed to a higher RI environment,the sensitivity of the sensor also can be improved.The RI of cyclohexane is 1.422 at room temperature.Compared to other thermal sensitive materials,the cyclohexane helps further improve the sensitivity of fiber optic SPR sensors.The experimental results show that the average sensitivity of the sensor is 14.7 nm/^oC,and the temperature detection range is 5-80 ^oC.The sensitivity of sensor is 25.7 at 5 ^oC.By improving the structure of the proposed temperature sensor,we propose and demonstrate a sensor cascaded dual-channel fiber SPR sensor based on Ge₂Sb₂Te₅,which can simultaneously measure temperature and RI.The RI sensing channel consists of a gold film.The temperature sensing channel is composed of gold,Ge₂Sb₂Te₅ and PDMS.When Ge₂Sb₂Te₅is coated on the surface of the gold film,the resonant wavelength is red-shifted.Therefore,this design effectively avoids band crosstalk.The experimental results show that the RI and temperature sensitivity of the sensor are 2781 nm/RIU and 5.88 nm/^oC.In order to verify the high measurement accuracy of the sensor,the thermo-optical coefficient of ethanol absolute is measured and calculated.The experimental results show that the measurement error of the sensor is less than 1.28%.The sensor has the advantages of high measuring accuracy,small size and strong stability.Therefore,it has potential applications in the fields of biochemistry,aerospace and ocean exploration.