| Optical fiber surface plasmon resonance sensor is a sensing technology which is based on optical fiber and the plasmon resonance sensing.It has lots of the advantages,such as high sensitivity,small size,easy to disposal and installation,remote online-monitoring and convenient to operation.Photonic crystal fiber?PCF?has novel optical properties and structural designability,which can effectively control the optical field to excite the SPR and provides the possibility for designing novel optical fiber SPR sensors.By introducing PCFs into SPR sensors,the sensors can offer the phase-matching condition between the transmission light and the SPR.In this paper,ESM-12 photonic crystal fiber is used as sensing fiber,by means of side-polished to making the D-shaped PCF,and deposit the gold films on the side-polished planes of the D-shaped PCF,Then,complete the fabrication of sensors.The performance of the sensor is studied by the on-line detection system.The main research work of this paper is as follows:1.A theoretical simulation of D-shaped ESM-12 photonic crystal fiber SPR sensor is establish by COMSOL Mutiphysics finite element analysis software.The effects of polishing depth and thickness of metal film on the sensitivity and loss characteristics of the sensor were studied.Results show that the RI sensitivity of the sensor decreases with the polishing depth h increase,but the sensitivities are almost the same regardless of the variation of h.What is more,with the increase of the film thickness T,the loss of the sensor decreases while the sensitivity is increases,when the thickness of the metal film between 30 nm and 60 nm.By contrast the performance of sensor which deposited gold film or silver film,it is found that which with silver film is in higher sensitivity.2.Based on the theoretical simulation,we fabricating the D-shaped ESM-12 photonic crystal fiber SPR sensor,and seting up an on-line transmission detection system.The D-shaped photonic crystal fiber was successfully fabricated by fiber side-polishing system,then depositing the metal sensing film on the polishing plane.After that,an on-line transmission detection system is built to test the sensing performance of sensor.3.The sensing performance of the D-shaped PCF-SPR sensor were studied,which is with the15mm of polish length,60 um of polish depth,and 45 nm of gold film.Experimental results show that the sensitivity of the sensor become better with the environmental refractive index increases when refractive index is between 1.3388 and 1.3638,and the maximum sensitivity of 2336.2 nm/RIU is achieved.After that,we verified the experiment results by simulation,it found that the measured results are consistent with the simulation results very well.What is more,a method of combining wavelength and intensity by resonance peak is proposed to improve the resolution of the sensor,which can reach 6.53 × 10-5RIU.4.Studying the influence of sensor by different polish length,there are four different polish lengths of sensors was fabricate in experience,which are 10 mm,15mm,20 mm and 25 mm respectively.With the polishing length L increases,the non-uniformity of the surface will increase significant,which cause the FWHM expand and the sensitivity of the sensor decreases.When the polishing length L is 10 mm and the refractive index range between 1.40 and 1.42,the average sensitivity of the sensor reaches 7381 nm/RIU.5.The temperature characteristic of the sensor is investigated.Results indicate that the SPR resonance peak shifted to the short wavelength with linear regular in 30 ? 90?,and the average temperature sensitivity of the sensor is 0.23416nm/?.6.Testing the repeatability and stability of the sensor.We selected the sensor which L is 20 mm to do the repeatability test at room temperature?24??.The resonance wavelength shift of each refractive index solution and each group of refractive index solution is calculated respectively,the minimum standard deviation (?SD) is 1.15 nm and 2.58 nm respectively,which indicate the sensor has good stability and repeatability.7.A D-shaped all solid PCF-SPR sensor is proposed.The polishing depth and refractive index sensitivity of D-shaped all solid PCF-SPR sensor are analyzed by simulation.It is found that the polishing depth has little influence on the sensitivity of the sensor,we also carried out corresponding exploration in experiments. |
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