The Theorical Analysis And Experiment On The Embedded-microstructure Fibres

The photonic crystal fibres(PCFs),also named as microstructured fibres,have many special optical properties.Due to the flexible structure,the optical properties of PCFs can be changed by designing different structures in the cladding or infiltrating different analyte into certain air holes,especially the air holes around the core.These kinds of optimized PCFs had special structures and functions.We designed and fabricated some special structures of PCFs,especially some kinds of embedded-photonic crystal fibres.Firstly,we analyzed the optical properties of PCFs which had different cladding and core-area structures theoretically.Then we designed and fabricated photonic liquid crystal fibres(PLCFs)and analyzed the optical properties.Finally,we designed a new method to measure the sensitivities of hydrophobic microstructured polycarbonate(PC)and polymethylmethacrylate(PMMA)fibres,the optical properties were analyzed in both theoretical and experimental method.The main topics of this thesis include four parts as below:1.Two special PCFs were designed and analyzed based on Finite Element Method(FEM).The first kind of PCFs was ring-cladding PCFs which had high nonlinear characters.The second kind of PCFs was square-lattice cladding PCFs which had high birefringence and flatten dispersion at the same time.2.The embedded PCFs were modeled and analyzed theoretically.A six cores mode convertor was designed and simulated.The structure parameters of this convertor were optimized in short and long wavelength respectively.After that,we calculated the single mode condition in different structure parameters of PLCFs,and based on it,a six cores PLCFs splitter was designed and optimized.3.Liquid crystal-filled PCFs were analyzed.Above anything else,one of six air holes in the first ring of cladding was filled with liquid crystal.Through changing the temperature and heating area,the position and intensity of output light can be controlled.Furthermore,the ratio of filling was also discussed.The liquid crystal was filled into all,half and a quarter of air holes in the cladding.The distribution and the changing of bandgaps with increasing temperature in different filling ratio were analyzed.4.The sensitivity of a new type of refractive index polymethylmethacrylate(PMMA)and Polycarbonate(PC)fibre sensor was measured by pumping the solutions into the satellite core.Moreover,the sensor could be reused because the position of fibre was fixed without cross-section damaging.The sensor had very good behavior of immunity on environment.The experimental and theoretical results matched very well.This thesis has some innovation as below:1.We designed a new kind of high nonlinear ring-cladding photonic crystal fibres.Comparing with the normal ring-cladding photonic crystal fibre,the nonlinear coefficient was improved significantly and the zero dispersion wavelengths also moved to short wavelength.The square-lattice cladding photonic crystal fibres had the properties of flatten dispersion and high birefringence together through changing the arrangement of the air holes around the core.2.We designed a new kind of mode convertor based on embedded photonic crystal fibres.The structure of this kind of mode convertor was optimized to fulfill the need in 0.65 m and 1.65 m.3.We designed and fabricated selective-filled PLCFs.The refractive index of liquid crystal was changed in different temperatures.Thus the position of output light,the shape of spectrum and the distribution of bandgaps could be controlled by temperature changing.4.We designed a new way to measure the sensitivities of polymethylmethacrylate(PMMA)and polycarbonate(PC)microstructure fibres.Based on a simple transmission setup,the sensitivities were measured without fibre damage.Experimental and theoretical results were fulfilled with each other.