| In the course of human development,the exploration for the world has never stopped,and the development for sensor technology has greatly promoted people's perception of the world.With the advent of the Internet of Things(IOT),people hope to use good-quality sensors and information and communication technologies to realize that all things can be interconnected through the Internet.Traditional large-volume and weak-function sensors suffer from disadvantages such as slow processing speed,large volume,and unstable performance.It is difficult to meet the needs of sensors in the era of IOT.The integrated sensors have atractted attentions due to their advantages of compact structure,multi-parameters sensing,large amount of information processing,and good sensing performance.Integration of sensor is a major trend in the development of sensing technology.How to further reduce the size of sensors,reduce mass production costs,improve sensing performance,and improve stability are key factors for the development of integrated sensors.The microstructured optical waveguide has the advantages of simple structure,small volume,and good sensing performance.It has been widely used in optical sensors,lasers,and other fields.It greatly reduces the size of the sensing structure and facilitates the layout of sensor.At the same time,the microstructured optical waveguide has the advantages of simple structure and good sensing performance.Its amazing research progress and huge market potential provide a great impetus for the miniaturization of sensors.In this paper,sensing technologies based on micro-structured optical waveguides are studied.The main research contents and achievements are followings.(1)The micro-fiber coupler(MFC)structure was studied,and the coupling process and transmission characteristics were modeled and analyzed.The MFC under weak coupling station with 3 ?m diameter of tapered waist and 25 mm of total tapered lengh were fabricated using "micro-heating brush" micro/nano fiber processing technology.The ammonia-sensitive material of silica gel was fabricated with different viscosity using chemical method.The technology of uniformly coating the silica gel on the tapered region of MFC was studied.The ammonia sensor based on the coated MFC was designed and its sensing performance was studied.The experimental results showed that the sensitivity can be achieved 2.23 nm/ppm,and the resolutions was 5 ppb,which was 103 lower that of conventional ammonia sensor based on coated fiber.The sensor exhibited good repeatability and gas selectivity.The thickness of the coating layer had a great influence on the sensitivity of the sensor,which proved that the sensitivity of the sensor can be controlled by controlling the thickness of the coating layer.At the same time,the temperature and humidity response of the coated MFC were analyzed.It was found that the sensor structure has good temperature and humidity frequency shift response.The sensitivity responsing to temperature was about 5.5 nm/? and the highest sensitivity responsing to humidity was 1.6 nm/%RH.At the same time,it was found that the fiber diameter error of ±0.5?m caused by MFC processing errors has a small impact on the temperature and humidity response,which proved that the coated MFC structure has large fabrication tolerance.The results lay a foundation for the development of the coating MFC structure as a miniaturized and integrated sensor.(2)The sensing structure of Ellipsoid and Fiber Bragg Grating(EFBG)was studied and its sensing mechanism and transmission characteristics were analyzed.Modeling analysis and experimental results showed that the ellipsoid structure was a good mode exciters and couplers in the EFBG structure.The Bragg reflection peak and large power cladding mode resonant peaks can be observed at the reflection optical spectra.The study fully explored the response characteristics of EFBG structure to different environmental parameters,studing the frequency shift response of different order resonance peaks in EFBG reflection spectrum to the refractive index(RI)and temperature.It was found that EFBG can realize temperature-insensitive refractive index sensing,the detecting range of RI can be achieced from 1.3352 to 1.37.The wavelength shift of cladding resonant showed linear relationship with RI in the range of 1.3352 to 1.37(the sensitivity was about 355 pm/RIU),and showed exponential relationship with RI in the range of 1.37 to 1.4425(the highest sensitivity can relize 4182 pm/RIU).The influence of the gap between the ellipsoid and FBG on the sensitivity was experimentally analyzed.In addition to the refractive index and temperature response,this paper also studied the response of EFBG to axial tension and bending curvature.Experimental results show that the resonance peaks with different order of the EFBG output spectrum have exactly the same frequency shift response to the axial tension.Power change of the cladding resonante peaks of the cladding mode is significantly higher than that of the Bragg reflection peak.(3)The silicon concentric dual-ring resonator(SCDMR)is studied.The transmission characteristics of the system are analyzed by finite-difference-time-domain(FDTD)method.The concentric double-ring resonator increases the internal loss of the whole ring resonator through the inner-ring waveguide,which helps to make the resonant cavity reach the critical coupling state.The output resonance peak has a higher Extinction Ratio(ER)and a larger quality factor(Q).The effects of resonant cavity parameters,such as SCDMR waveguide size,straight waveguide-outer ring waveguide spacing,and inner-outer ring waveguide spacing,on waveguide sensitivity,extinction ratio,quality factor,and sensor sensitivity were analyzed.The optimal balance between the two values of sensor performance and transmission loss determines the structural parameters of the SCDMR.At this time,the output resonance peak ER can reach 30 dB and the Q value can reach 1.7×105.The refractive index sensor based on SCDMR is designed to detect sucrose solution and NaCl solution,and the light field distribution under resonant condition was analyzing.When the designed resonator response to NaCI solutions,the sensitivity is 376.42 pm/%,the detection limit is 0.53%;When the designed resonator response to sucrose solutions,the sensitivity is 369.3 pm/%,the detection limit is 0.54%?... |
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