Research On Output Performances Of Continuous Wave And Mode Locking Tm-doped Fiber Lasers

The fiber laser is developed rapidly in recent years, due to its stability, maintenance-free,compact structure, small thermal effects, low threshold power, and high conversion efficiency.The output wavelength of Tm fiber laser is not only in eye-safe waveband, but also in atmospheric windows. Hence it is widely used in many areas, such as the free space communications, the atmospheric remote sensing, the material processing and surgical operation. Therefore, the study of Tm fiber laser is of great significance. In this thesis, two aspects of the Tm-doped fiber laser are represented,including the continuous wave and the mode locking operations.First,the continuous wave Tm fiber laser is investigated. Based on the rate equations and the power propagation equations of the Tm fiber laser,the output performance of the continuous wave Tm fiber laser is numerically simulated. The effects of pump power,fiber length and concentration of Tm ions are analyzed. Three kinds of cavity have been carried out, and the output spectra and the slope efficiency are measured.Second, the mode locking Tm fiber laser is studied. In theory, based on the Jones matrix of the nonlinear polarization rotation, the analytical expression of the transmittance is obtained. In experiment, when the cavity length of Tm-doped fiber ring laser is 80m and 180m,the mode locking is realized by adjusting the three rings polarization controller.The repetition rates of 2.552MHz and 1.087MHz are achieved in Q-switched and mode locking operation respectively. The pulse width can be decreased to Ins. On the basis of realizing continuous mode locking, the high order harmonic mode locking can be achieved by adjusting the angle of three rings of the polarization controller and increasing the pump power.The highest order harmonic mode locking can reach to 8th order. In addition, the switching of the output wavelength between 2034nm and 2044nm is realized.Finally, the shortcomings in the progress of experiment are discussed, and the solutions are given.