Double-clad Photonic Crystal Fiber Lasers And Wavelength Converters Research

The Photonic crystal fiber (PCF) has called more and more attentions for its profound physic background and important applications, and it has become a new focus of the optical research domain. With the unique structure and excellent properties, PCF has provided a novel kind of optical transmitted medium and optical device. With the progress of research and technology, PCF is likely to be the eminent new generation optical device for signal transmiting/processing and exchangeing in the fiber communication systems.This dissertation is based on the project"Basic investigation and innovation of photon-electron functional devices based on PCFs", which is financially supported by the National Basic Research Program of China Foundation (973). The targets of the project are: to discover new tuning mechanisms and nonlinear theories of PCFs, to develop photon-electronic communication devices based on PCFs, and to develop integrated fiber devices based on PCFs.Based on the targets of the project this dissertation mainly studied fiber lasers and integrated fiber devices. The detailed works are listed as follows:Firstly, the basic methods of numerical simulation have been introduced. Especially, the basic idea and analyzing process of the finite element method (FEM) have been discussed and the intrinsic equation has been deduced. Moreover, the modes and propagation constants of the PCF have been numerically analyzed by FEM with gradual changed air hole.Secondly, the mode distributions of PCFs with irregular structures have been investigated by FEM. The birefringence induced by two kinds of irregular structures: positional displacement and geometrical deformation of air hole have been calculated, and the relationship between the birefringence, irregular ratio and fiber structure parameters has been concluded. The results after the numerical simulation are believed by us to have a guiding significance for the design and manufacture of PCF.Thirdly, a high power cladding pumped PCF laser whose output power exceeds 10W has been demonstrated using Fabry-Perot resonance cavity configuration. The output power and slope efficiency of a double-clad ytterbium-doped large mode-area PCF laser are 2.65W and 57% respectively, and the highest power is up to 11.69 W. The achieved width of spectrum is very narrow,which demonstrates the excellent properties of this fiber lasers. Moreover, the working mode of the laser still be a single-mode although a large scaled fiber are used, the reason is that the fiber has an excellent mode-controlling ability.The amplified properties of ytterbium-doped large mode-area PCF are also investigated.Fourthly, an all fiber cladding pumped Er3+-Yb3+ co-doped fiber laser has been demonstrated using taper fiber bundle (TFB). The output powers of the forward and backward pumping configuration are 80mW and 50mW, respectively. And our experiments indicates the backward pumping gives out better flattend gain.At last, a scheme of all-optic wavelength conversion are demonstrated, which is based on four-wave mixing (FWM) in the PCF whose zero dispersion wavelength is at about 1550nm and the nonlinear coefficient is ~11(Wkm)-1. The phase match condition of four-wave mixing in microstructure fiber has been discussed, and the wavelength range that satisfies the phase match condition has been summed. By use of 20m-length microstructure fiber, the wavelength conversion of signals over a ~50nm bandwidth has been reliably achieved, under the condition of changing the wavelength of pump laser while fixing the wavelength of signal. And the measured maximum FWM-to-signal ratio is -7dB.