Theoretical And Experimental Study On High Power Erbium - Ytterbium Co - Doped Fiber And Super Fluorescence Output

The creation and development of fiber lasers, lasers which comprise rear-earth doped fibers for optical gain and Fabry-Perot resonators for optical feedback, are considered to be a revolution in the laser field. High-power cladding-pumped fiber lasers attracted a lot of attention in recent years owing to their various advatanges over traditional gas and solid lasers. In particular, high-power Er,Yb co-doped fiber lasers and amplifiers, with radiative transitions around1.5μm corresponding to the third low loss transmission window in silica fiber and the eye-safe range, have wide applications in the field of fiber communication, remote sensing, fiber sensing, national defense and so on. In this thesis, the output performances of high-power Er,Yb doped fiber lasers and superfluorescent sources are discussed. Experimental results and numerical analyses are presented.1. Lasing characteristics of the Er,Yb fiber was evaluated with both ends perpendicularly-cleaved and feedback for laser oscillation provided by the3.6%Fresnel reflections. The laser generated77W of output at1.55μm for209W of launched pump power at975nm, corresponding to an average slope efficiency of-37%.2. High-power operation of a cladding-pumped Er,Yb co-doped broadband superfluorescent fiber source in the1.55μm spectral region is reported. Over16W of single-ended amplified spontaneous emission output was generated employing a simple, all-fiber geometry without the use of a high reflectivity mirror or seed source. The wavelength range spanned from～1531nm to1568.5nm with a bandwidth (FWHM) of～17nm and the corresponding slope efficiency with respect to launched pump power at975nm was30.7%.3. Effect of the fiber temperature on lasing performance is investigated in high-power, cladding-pumped, double-clad Er, Yb co-doped fiber laser system. A three-layer symmetric cylindrical model is applied to describe the temperature distribution of the fiber under natural air convection. Radial temperature distribution of the fiber is calculated with consideration of the quantum defect heat, the heat from the absorption of spontaneous emission, and the convection and radiation at the heat transfer boundaries. It is showed that increasing the fiber’s temperature is an effective strategy to suppress1μm parasitic lasing and improve the lasing performance at1.5μm, a similar phenomenon is found with enhancing doping concentrations of the two ions and decreasing the reflectivities at the fiber ends.