Study On The Properties Of Photonic Crystal Fiber

Photonic crystal fibers (PCFs) have excellent birefringent properties, the high birefringent PCFs have important applications in optical communication, precision optical instruments, fiber optic sensing and other fields, which have attracted much attention recent years. Especially in the optical systems, people are increasingly using high birefringent PCFs to achieve the miniaturization and all optical of the system. Therefore, designing new type of high birefringent PCFs are very improtant.This paper focus on the PCFs with high birefringence and high nonlinearity, three kinds of novel PCFs with these properities are proposed, and the full-vector finit element method is used to numerically simulate and theoretically analysis their characteristics. The main content is below:1. The concepts, difference compared to the traditional fiber, classification, manufacture methods, application of PCFs and the present research situation of the high birefringent PCFs are briefly introduced.2. The simulation software COMSOL which is based on the full-vector finit element method is used to investigate the birefringence, nonlinearity, confinement loss, group velocity dispersion and other characteristics of PCFs. Using novel structure or special materials to design PCFs to meet the continuous development of the optical field.3. A novel type of asymmetric elliptical-hole photonic crystal fiber with a central defect hole is proposed. The full vector finite element method is adopted to investigate its birefringence, dispersion and non-linear characteristics. By changing angle of the first layer elliptic hole, birefringence properties of the structure is strengthened, which also can improve the dispersion performance of the structure at the same time. The analysis results demonstrate that the birefringence is 3.05×10-2 at the wavelength of 1.55μm, and high nonlinear coefficients in X,Y polarization directions respectively are obtained by setting suitable structure parameters. Furthermore, while maintaining the high birefringence, the proposed PCF also has negative flat dispersion of nearly 550nm from 1000nm to 1550nm.4. A particular photonic crystal fiber designed with all circle air holes is proposed. The complex hybrid air holes design is avoided without degradation of performance, and, since all air holes are circular, this PCF could be fabricated by the stack and draw method or the performs drilling method. The simulation results indicated that the proposed PCF can realize high birefringence (up to 10-2), high nonlinearity(50W-1·km-1 and 68W·1km-1 in X and Y polarizations respectively) and low confinement loss (less than 10-3dB/km at 1.55um wavelength).5. A hybrid AsSe2-As2S5 photonic crystal fiber with elliptical solid core and normal circle air-holes cladding is proposed here. The core and cladding are made of AsSe2 glass and As2S5 glass, respectively. From the simulation results, it is shown that the proposed fiber is single-mode above 1.5 μm and has high birefringence up to 5×10"2, nonlinear coefficient of 9.8×104W-1·km-1 and confinement loss of 0.3 dB/km at 1550nm wavelength.