Theoretical And Experimental Research On 1.06μm Yb³⁺-doped Phosphate Fiber Laser

Fiber laser has many advantages, such as low threshold, low noise, high SNR, high stability and compact structures. It has wide applications in fiber communication, coherent measuring, fiber phase sensor, and optical spectroscopy, etc. Because of simple and far separated energy levels of Ytterbium ion, it is difficult for non-radiation cross-relaxation and concentration quenching of Ytterbium ion to occur, and there is no excited state absorption at pump wavelength and laser wavelength. Because of all the unique characteristics of Ytterbium ion mentioned above, it has become the most interesting research subject in sensing and communication these years. This thesis focuses on theoretical and experimental study of 1.06μm Ytterbium doped phosphate fiber laser.The thesis discussed the selection technique of longitudinal and transverse mode, and designed the resonator of 1.06μm Ytterbium doped phosphate fiber laser.Numerical simulation about the working process of fiber laser was demonstrated based on the Ytterbium doped phosphate fiber, the Ytterbium doped energy-level-transition model and the rate and transition equations. In the numerical computation, the distribution of pump and signal light along the axis of fiber, the influence of different parameters on output characteristics curve were simulated and analyzed.The thesis analyzed the theory of relaxation oscillation noise, and studied the influences of different fiber lengths, intra-cavity losses and pump power on it through numerical simulation. The methods of noise reduction were proposed in the end.The thesis measured and analyzed each optical component used in the experiment to reassure the best working conditions of the fiber laser. It measured the output and spectrum parameters under different resonator structures and different length of Ytterbium doped phosphate fiber laser, and relatively stable spectrum and low noise were achieved.In order to attain larger longitudinal interval, the structure of the Ytterbium doped phosphate fiber laser with the best performance was composed of the single mode 975nm LD pumping and the cavity, which was composed of fiber grating, dichroic mirror and 2cm homemade Ytterbium doped single-mode phosphate fiber. The pumping threshold was 30mW, the maximum output power was 55mW, the slope efficiency was 9.5% and the central wavelength of the output laser was 1063.5nm.