Research On The Refractive Index And Temperature Measurement Based On Plastic Optical Fiber SPR Sensor

The phenomenon of surface plasmon resonance(SPR)is widely used in the field of biosensing due to its high sensitivity to changes in the refractive index of the medium.Among them,fiber-optic SPR sensors have been widely studied due to their strong resistance to electromagnetic interference,small size,remote monitoring capability,and ease of testing in small spaces.However,in refractive index detection,the ambient temperature has a significant impact on the measurement results.If only the refractive index is detected,the accuracy of the measurement results cannot be guaranteed.Therefore,the development of fiber-optic SPR sensors capable of simultaneously measuring refractive index and temperature is particularly important.Currently,most reported fiber-optic sensors capable of detecting both refractive index and temperature are based on glass optic fibers.However,after structural modification,glass optic fibers become relatively fragile,limiting their application in the sensing field.In this paper,two SPR sensors capable of simultaneously detecting refractive index and temperature were prepared using plastic optic fibers.The main contents of the paper are as follows:A double side side-polished U-shaped plastic optic fiber SPR sensor was proposed for simultaneous measurement of refractive index and temperature.The sensor obtained a stable U-shaped structure using a thermal shaping process,and then the two sides of the U-shaped area of the plastic optic fiber were polished by using a grinding device.A layer of gold film was deposited on the polished area to excite SPR,and a layer of PDMS film was prepared in one of the SPR excitation areas to obtain a temperature sensing channel.The influence of different polishing angles and depths on the sensor performance was experimentally studied,and the structural parameters of the sensor were optimized.The proposed sensor has a refractive index sensitivity of 1258 nm/RIU within a refractive index range of 1.34-1.37 RIU,and a sensitivity of-0.596 nm/℃ within a temperature range of 30-80℃.A plastic optical fiber SPR sensor based on side polishing and V-groove structure is proposed.Theoretical analysis and experimental investigations demonstrate that the Vgroove structure can enhance the SPR excitation effect,change the excitation angle range of SPR,and narrow the SPR spectrum width.Based on this structure,simultaneous detection of refractive index and temperature is achieved by introducing a thermosensitive materialPDMS.The effects of V-groove depths,V-groove angles,and side polishing depths on the characteristic spectra of the sensor are experimentally studied and the sensor performance is optimized.The experimental results show that within the range of refractive index from 1.335 to 1.37 RIU,the refractive index sensitivity of the proposed dual-parameter detection probe can reach 1546 nm/RIU.Meanwhile,the temperature sensitivity of the sensor can reach-0.83 nm/℃ within the temperature range of 20-80℃.