| Polarization-maintaining fibers (PMFs) have been widely applied for telecommunication, fiber-optic sensor and integrated optics for information process. Generally, conventional stress PMFs, such as Panda and Bow-tie, have low stress birefringence due to stress effects of stress operation cell in core region and complicated fabrication techniques, temperature instability and weak resistance to nuclear radiation owing to GeO2-doped core and B2O3-doped stress regions. So, conventional PMFs are not able to satisfy the requisitions of modern communication system. Photonic crystal fibers (PCFs), consisting of single material and an array air-holes running along the entire fiber length, can be obtained with high birefringence and single mode operation at larger wavelength range by simple tuning the diameter, shape, position and array mode of air-holes. So it is very easy to induce the larger different of refraction index between the fibers' core and the cladding. Compare with conventional PMFs, photonic crystal polarization maintaining fibers (PM-PCFs) have the advantages of higher resistance to nuclear radiation, better stability of temperature and polarization and lower polarization mode dispersion. Hence, PM-PCFs have potential application in the fields of all optical networks, fiber-optic gyroscope, fiber-optic sensor and optical fiber laser.However, the application of photonic crystal PMFs based on silicon material is always restricted owing to the complexity of the capillary stack-and-draw fabrication technique. In 2001, Dr. Martijn A. van Eijkelenborg et. al. of University of Sydney of Australia reported the research results to develop various PCFs based on polymer for the first time. These results provide a kind of new idea for developing PCFs. We are enlightened deeply on the research of photonic crystal PMFs by them. In this dissertation, we first concentrate on the fabrication technique and the draw-stretching technology of preform of polymer PCFs. For the more, the optimum structure of polymer PM-PCFs was studied on the basis of theory. The polymer PCF with elliptical core hexangular symmetry structure was fabricated successfully under the method of in-situ monomer polymerization and sleeving draw-stretching based on methyl-methacrylate (MMA) material. Finally, we measure the optical property and polarization characteristics of the fabricated fiber. The main achievements are listed below:(1) The idea of adopting full vector plane wave method (FV-PWM) to analyze polarization property of high birefringence PM-PCFs was presented by studying the theory model of PCFs. According to the equation of Maxwell, we divide E and H fields, and the dielectric permittivity by using Fourier series, and set up the theory modal of plane wave to analyze PCFs with band-gap effect. In the end, the theory modal of plane wave was applied in the PCF with index-guiding.(2) According to FV-PWM, the four kinds of PCFs were numerical simulated based on polymer. They were the elliptical core hexangular symmetry polymer PCF, the elliptical core non-hexangular symmetry polymer PCF, the rectangular lattice polymer PCF and the single-polarization single-mode polymer PCF.(3) A new kind of highly birefringent index-guiding PCF with elliptical core nonhexangular symmetry cladding was proposed for the first time. The polarization characteristics and mode field property of the PCFs being made of polymer material are numerically simulation to adopt FV-PWM. The results showed that the birefringence of the fiber had been induced by asymmetries of both the cladding and the core. Moreover, the polarization characteristics is strongly dependent on the non-symmetry ratio of cladding ofη=b/Λ, here, b is the holes-spacing of y direction,Λis the holes-spacing of x direction, the holes-diameter is defined as d. WhenΛ= 2.3μm, the ratio of holes-diameter and holes-spacing is d/Λ=0.4, and the non-symmetry ratio of claddingη=0.4, the fiber is possible to operate in single mode regime at wavelength ranges of near infrared and visible with high birefringence of 1.294×10-3, and limited polarization mode dispersion effectively.(4) A new kind of PCF fabrication technique with independence knowledge property right is developed, including the fabrication and the draw-stretching technologies of the preform. The in-situ MMA monomer polymerization technique, for the first time, is transplanted to fabricate PCFs preform in China. A series of investigations have been carried out in the process of fabricating PCF, which included the preform fabricating and draw-stretching, the relationship of time and temperature in the polymerization reaction. The PCF preform with elliptical core hexagonal symmetry structure with diameter of 70 mm, hole-diameter of 2 mm and hole-spacing of 5 mm was developed successfully. Additional, the sleeving draw-stretching technique of preform was set up, and the elliptical core hexagonal symmetry structure polymer PCF with fiber diameter of D=125±5μm, average holes-diameter of 3.5μm and average holes-spacing 9.4μm was fabricated successfully. The temperature field distribution in the oven of preform draw-stretching and fiber draw-stretching were investigated.(5) The optical and polarization properties of polymer PCF with elliptical core hexagonal symmetry structure from sleeving draw-stretching technology were characterized. Experimental results showed that the fiber had good characteristics such as better machine flexibility, smaller numerical aperture (NA), larger mode field diameter and weaker birefringence effect. Its transmission loss is 11.5 dB/m at wavelength of 632.8 nm, its bend radii is 10 mm, the bend loss is low when the bend radii more than 10 mm. At the same time, its birefringence is only 4.65×10-7 at wavelength of approaching 650 nm.The results above-mentioned provide useful reference in both the theoretical and experimental aspects for further studying the fabrication technology and the method of measuring polymer PCFs.The work was supported by the Natural Science Foundation of China under Grant No. 60437020.
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