The Theoretical And Experimental Study Of Photonic Crystal Fibers

Since the photonic crystal fiber was firstly demonstrated by As J. C. Knight in 1996s, it soon attracted considerable attention due to its novel characteristics (which are completely different from the ones of the conventional fibers) and potential applications. PCFs have now been one of research areas that rapidly grow during last decade.It's very difficult to give a qualitative or analytical analysis for a PCF due to its complicate structure, so numerical simulation is often necessary when one needs to analyze or design the characteristics of PCFs, such as dispersion, loss and energy confinement, etc. As one of efficient numerical techniques developed for PCFs, the two-dimensional compact FDTD method is introduced in this paper. However, the existed FDTD method can not deal with the material dispersion. By making use of Sellmeier Formula for fused silica, we propose an effective way to introduce the material dispersion into Maxwell's equation in time domain. To our knowledge, it is the first time to successfully extend the 2D compact FDTD as a mode solver to deal with the material dispersion. The extended FDTD method still keeps the previous advantages of a compact FDTD method.Birefringence is one of most remarkable properties of PCFs. In this paper we propose a new elliptical-hole PCF with a core formed by double defects. We carefully analyze characteristics of this new PCF, such as the field pattern, birefringence, and single-mode operation. It is shown that such a PCF posses a rather high birefringence, as its birefringence is resulted from the asymmetries of both the core and cladding, i.e., a global effect. This novel fiber can be designed to operate in single mode while it has a high birefringence. So it_can be well used as a single polarization fiber or be applied to fiber sensors.Based on our experimental conditions, the experimental studies on PCFs are made and are presented in this paper. First, by using a 25 m long nonlinear PCF, the supercontinuum is generated and is carefully analyzed experimentally. Compared theother experiments previously reported in literature, the input pulse used in our experiment has a rather low average power, and its FWHM is about 230fs. We improve supercontinuum efficiency with the long length of PCF and thus effectively decrease the threshold of supercontinuum generation. Second, a Sagnac loop filter based on the birefringence of a PCF is designed and is used to construct an all-fiber multi-wavelength Raman fiber laser in this paper. Stable lasing at multi-wavelengths is observed and the power distribution among different lasing can be effectively tuned by ajusting the pump power.