Research On The Sensing Properties Of Lossy Mode Resonance-Based Fiber Optic Sensor And Its Application On Humidity Measurement

Lossy Mode Resonance(LMR)is a relatively new physical optics phenomenon proposed in recent years,which have attracted considerable research and development interest because of their distinct advantages such as high sensitivity and label-free measurement.LMR sensors based on optical fiber have also been used in in many parameter measurement.However,few comprehensive research on LMR appears in our country at present.Hence,aiming at analysing the sensing properties,developing the fabrication process,optimizing the performances of sensors,novel LMR optical fiber sensors deposited titanium dioxide(TiO2)or tin dioxide(SnO2)are proposed in this thesis.This thesis has completed the following main research work contents:(1)The basic principle of loss mode resonance and the characteristics of LMR excited film are illustrated in this paper.Further,the sensing principle of optical fiber LMR sensor and optical fiber humidity based on lossy mode resonance are analyzed and researched.Several evaluation indexes are presented to measure sensing properties of sensors,which lay the foundation for later fabrication and analysis of sensors.(2)The LMR sensing model is established through COMSOL Multiphysics and Matlab,which theoretically illustrates the effect of different membrane structures on sensing performances.The measurement for the variations of RI is realized based on the proposed and prepared sensor,and the basic property towards the LMR sensing are analyzed and researched.Nanoparticles are further used in performance optimization of sensors.Experimental results show that the refractive index measurement sensitivities of sensor embedded gold nanoparticles can reach to 6405 nm/RIU,has increased by 177%compared with original sensor.(3)LMR optical fiber sensor deposited SnO2 is proposed to analyze the influence of film properties on sensing performances and fabricated by improved layer-by-layer self-assembly method.Nanoparticles are also used in performance optimization of sensors.The simulation and experiment results show SnO2 sensor has not only the characteristics of common LMR sensors but also higer sensitivity and wider resonant dip.In addition,the refractive index measurement sensitivity of sensor coated with gold nanoparticles can reach to 4704 nm/RIU,has increased by 55.9%compared to original sensor.(4)The applications of the proposed sensor in the measurement of humidity are realized based on the polyvinyl alcohol material.This new relative humidity sensor based on lossy mode resonance is designed and fabricated.By further constructing the measurement system,the relative humidity measurement properties are tested and analyzed.Experimental result shows that the sensitivity can reach to 2.15 nm/%RH(20%RH-60%RH)and 3.98 nm/%RH(60%RH-90%RH),enhancing by 38.2%in high humidity condition and realize the response to humidity in low humidity condition.Furthermore,the insensitivity of LMR sensor to temperature change is verified,which overcomes the shortcoming of other fiber optic humidity sensors.