Study On Novel Photonic Crystal Fiber Sensor And Active Intra-cavity Fiber Sensing Technology

In recent years,photonic crystal fibers(PCFs)have been studied extensively and deeply due to their unique optical properties and structure advantages.Novel hollow-core photonic crystal fibers(HC-PCFs)based gas and liquid sensors have become a research hotspot in the sensing field because they are easier to realize all-fiber,high sensitivity,long-distance and distributed sensing when compared with traditional sensors.Furthermore,high-performance fiber laser based active intra-cavity sensing technology can realize high-sensitivity and high-resolution sensing.This paper focuses on the research of HC-PCF sensors and high-performance active intra-cavity fiber sensors,the main research contents and innovations are listed as follows:1.Research on high sensitivity HC-PCF gas sensor.Based on the structure of commercial HC-PCF,a gas sensor based on HC-PCF with the floriated central hole is designed and optimized.Numerical investigation with finite element method shows when the incident light wavelength is 1.56?m,the HC-PCF gas sensor with floriated central hole could obtain the highest relative sensitivity coefficient of 0.9998,which is better than 0.9435 of the typical circular central hole.2.Research on surface plasmon resonance(SPR)based HC-PCF liquid refractive index(RI)sensor with large detection range and high linearity.A liquid RI sensor realized by selectively coating gold film is proposed and numerically simulated.The sensor can work in a large RI range from 1.27 to 1.45 at the near-infrared region,overcoming the limitation of 1.42 as other reported side-hole-filled PCF based SPR sensors.Moreover,the relations between RI and the resonance wavelength are highly linear with an average spectral sensitivity of 5653.57 nm/RIU.3.Theoretical and experimental study on dual-wavelength ring-cavity fiber laser based PCF gas sensor with high sensitivity.A sensitivity enhanced active intracavity-absorption gas sensor based on the phenomenon of laser mode competition is demonstrated by theoretical simulation and experimental research of the dual-wavelength fiber laser.When the two-meter long HC-PCF is filled with 1000 ppmv acetylene,a sudden intensity decrease of 38.6 d B at sensing wavelength can be achieved,resulting from the mode competition phenomenon between the sensing and reference wavelengths.The minimum detectable acetylene concentration of 29.53 ppmv is obtained,one order of magnitude higher than previous similar works.4.Research on narrow-linewidth single-frequency fiber laser based high-resolution active intracavity temperature sensor.A high-resolution temperature sensor based on optical heterodyne spectroscopy technology by virtue of the narrow linewidth characteristic of single-frequency fiber laser is studied.In the experiment,when the single-frequency ring fiber laser has a Lorentzian-linewidth<1 k Hz and the temperature sensor operates in the range of 3-85°C,a wavelength sensitivity of 14.74 pm/°C is obtained.Furthermore,a frequency sensitivity as high as 1832 MHz/°C and a resolution of 5×10^-3°C is demonstrated through optical heterodyne spectroscopy technology in the range of 18.26-18.71°C with the figure of merit up to 3.1×10⁵.