Research On Sensing Technology Based On Microchannel Photonic Crystal Fiber

Surface Plasmon Resonance（SPR）is a physical optical phenomenon that occurs at the metal-dielectric interface,and since the SPR phenomenon is very sensitive to small changes in the refractive index（RI）around the metal film,a highly sensitive refractive index sensor can be realized.In the past few decades,SPR-based photonic crystal fibers have gradually become a new sensor that can be used in medical,biological and chemical fields due to the advantages of flexible structural design and high sensitivity.The size of the cladding air holes of photonic crystal fibers as well as the air hole spacing can be adjusted according to requirements.However,due to the low coupling strength of the core mode and SPP mode,the difficulty of controlling the sensor detection range,and the difficulty of realizing multiple parameter sensing in optical fiber sensors.In this thesis,in view of some shortcomings of SPR-based fiber sensors,different photonic crystal fiber structures are designed,and simulation experiments and numerical analysis are carried out by finite element method.In the chapter three of this thesis,a dual-core photonic crystal fiber sensor based on external microchannel structure is proposed,the sensor uses gold（Au）as the plasmonic material,the sensor realizes the sensing detection of visible light to near-infrared region of 562 nm-1413 nm,and achieves wavelength sensitivity of33600 nm/RIU and resolution of 2.97×10^-6 RIU in the refractive index detection range of 1.33-1.44,and the maximum figure of merit（Fo M）obtained is 961.In addition,this thesis studies the two structures of microchannel coating and plane coating,which can play an advantage in different detection ranges.In the chapter four of this thesis,a D-shaped photonic crystal fiber sensor based on external microchannel structure is proposed,using indium tin oxide（ITO）as plasmonic material,which realizes sensing detection in the near-infrared region of1554 nm-2006 nm,realizes a specific refractive index detection range of 1.320-1.355,wavelength sensitivity and resolution reaches 25000 nm/RIU and 4×10^-6 RIU.The detection range and wavelength sensitivity of the sensor can be controlled by changing the thickness and microchannel size of the indium tin oxide film,and the structural parameters can be selected according to the actual application scenario.In the chapter five of this thesis,a D-shaped dual-core multi-parameter photonic crystal fiber sensor based on internal microchannel structure is proposed,which obtains multi-parameter sensing capabilities by using plasmonic material gold and functional material magnetic fluid.Numerical analysis shows that the sensor can sense three parameters:refractive index,magnetic field strength and temperature,at1.57 nm/Oe,-1 nm/°C and 7600 nm/RIU in the detection range of 22-250 Oe,8-60°C and 1.38-1.42 RIs.The semi-annular gold film of the internal microchannel makes refractive index sensing,magnetic field strength sensing and temperature sensing fundamental modes independent of each other,thus making the sensor better adapted to various application scenarios.