Research On Fabrication And Sensing Characteristics Of Micro-hole Structure Plastic Optic Fiber Surface Plasmon Resonance Sensor

Surface plasmon resonance(SPR)sensing technology can be used to detect small changes in the refractive index(RI)at the dielectric metal interface with high sensitivity and fast response.The fiber optic based SPR sensing technology have been widely studied due to their advantages of strong anti-interference,small size,available for real-time and remote monitoring.At present,most optical fiber SPR sensors are based on quartz fiber,but due to the physical property of quartz material,the fiber sensor probe is difficult to maintain good mechanical strength after structural modification and easy to be damaged.Compared with quartz fiber,plastic optical fiber(POF)has the advantages of larger diameter,better mechanical strength,easy operation and good flexibility,which has broad application prospects in sensing fields.In this paper,the SPR sensor with micro-hole structure fabricated with POF is proposed.The main work in this dissertation are as follows:A side-polished POF based SPR sensor with one micro-hole was proposed and fabricated.The RI sensing characteristics and temperature response characteristics of the sensor were studied theoretically and experimentally,and the influence of structural parameters on the sensing performance of the sensor was analyzed.It can be indicated from the results that when the RI of the measured liquid is 1.43,the polished depth and length are 200 μm and 30 mm respectively,the sensitivity of the POF sensor with the hole diameter and depth of 0.65 mm and 1mm can reach 4713.86 nm/RIU when the micro-hole is not filled with liquid.When the micro-hole is fully filled with liquid,the sensitivity of the SPR sensor can reach 4064.22 nm/RIU.For the temperature response,the micro-hole structure makes the POF sensor more sensitive to temperature.Experimental results shows that a sensitivity of-1.43 nm/℃ can be obtained in the temperature of 20 ℃ to 60 ℃.The experimental results also show that the micro-hole has significant changes in the intensity of the normalized transmission spectrum,and the simultaneous measurement of refractive index and liquid level can be realized by fabricating multi-holes structure.A double-parameter SPR sensor for simultaneous measurement of RI and liquid level based on the multi-holes POF was studied.For the proposed sensor,the liquid RI can be measured by monitoring the shift of the resonant peak wavelength,and the liquid level can be measured by monitoring the change of the resonant peak intensity.The experimental results show that the sensor gives an RI sensitivity of 2058.93 nm/RIU in the RI range of1.335-1.40,and a measurement resolution of 5 mm within the liquid level range of 0-25 mm.When the RI of the measured liquid is 1.335,the sensor has a liquid level sensitivity of 0.00755/mm,and when the RI of the measured liquid is 1.37,the liquid level sensitivity of the sensor is non-linear,and the maximum sensitivity can reach 0.01496/mm.In addition,the results show that the proposed sensor has a very small cross sensitivity for the RI and liquid level measurement.