| Lanthanon-doped fiber laser and ultrafast technology have become two important fields in optics in recent years. This thesis is mainly concentrated on combining the excellent technologies from the two fields. Based on the National 863-416 projects "The study of key technologies on the Yb-doped fiber laser", both the passive mode-locked Yb~3+-doped fiber ring laser and conventional Yb~3+-doped fiber ring laser with high performance characters for the front-end system of Shenguang- III device have been researched. Theoretical analysis and the experiments are both studied. The relationship between the important characteristics of the Yb~3+ doped fiber laser (such as threshold power, output power and gain ) and laser parameters (such as pump power, fiber length, mirror reflectivity, output coupler ratio and Yb~3+ concentration) is deduced in details. The stability, pulse-width characteristic and self-stating action are analyzed. The conventional Yb~3+-doped fiber ring laser and the passive mode-locked Yb~3+-doped fiber ring laser with high performance are manufactured. A Yb~3+-doped fiber ring laser with the all fiber loop-cavity structure has been brought forward using the chirped fiber grating. Grating pairs are designed to compress the pulse. The signal source of Yb-doped amplifier using in free-spce optical communication has been designed and made out. Characteristics of the tunable laser are analyzed by the PSP theory (principal state of polarization, PSP), the Yb~3+-doped fiber ring laser generating continuous widely tunable pulses is fabricated. The follows are the contents and results in this thesis:1. Omitting the ASE, according to the rate equation, expressions of the Yb~3+-doped fiber laser's threshold value, slope efficiency and output power have been deduced. The characteristics of the Yb~3+-doped fiber laser pumped by the laser of 980nm have been simulated. The relations of performance parameters and structure parameters have also been studied. The results show that the performance parameters of the laser are influenced by the structure parameters obviously. The choose of the structure parameters has important meaning to the design of the laser.2. A highly-doped Yb~3+ fiber ring laser with short cavity has been presented in this thesis. Laser of 1053.24nm with the pulse width of 0.06nm has been obtained. The pump threshold power is 55mW and the maximum output power is 24.5mW. The slope efficiency is 15.1%. It can work stably for a long time and has the potential value on the front-end system of the ICF.3. According to the principal mode-lock equation, theories on the two kinds of typical mode-locked lasers (mode-locked by fast saturable absorbers and mode-locked by fast and slow saturable absorbers) are analyzed. The influences ofthe pulse width, chirp, bandwidth, loss, group velocity dispersion (GVD), self-amplitude modulation (SAM) and self-phase modulation (SPM) to the laser are discussed. The analysis has provide the theory of obtaining the ultrafast pulse by the Yb3+-doped fiber laser. Results show that positive dispersion increases the chip and the width of mode-locked pulses, and it is necessary to reduce incavity positive dispersion as much as possible to obtain short pulse.4. The self-starting action and the stability of the mode-locked Yb3+-doped fiber ring laser have been analyzed using NLS (Non-linear Schrodinger) equation. Results show that mode-locked laser can self-start much more easily with higher third-order nonlinear gain coefficient and longer gain relaxation time. It also shows that better filter effect, larger dispersion, larger saturable power of the gain medium, larger small signal gain and smaller loss benefit to the self-starting of the laser. Appropriate pump power and output couple ratio can increase the stability of the laser.5. The passive mode-locked Yb3+-doped fiber ring laser has been designed and turned out with high concentration Yb3+-doped fiber as gain medium. Using the nonlinear polarization rotation (NPR) effect of the fiber, self-starting stable mode-locked pulse of several ps is obtained. The center wavelength of the mode-locked pulse is 1046.14nm with 3dB bandwidth of 6.01 nm, 20dB bandwidth of 16nm and repetition rate of 20MHz. The output power can reach 25mW and the laser restrains the sideband modes very well. Also the mode-locked pulse with the center wavelength of 1056nm and 3dB bandwidth of 11.7nm is achieved.6. Using chirped fiber grating to compensate fiber dispersion and compress pulse, a novelty mode-locked Yb-doped fiber ring laser with all fiber structure has been designed. With the coupled-mode theory, the influences of some parameters ( such as grating length, coupled functions and chirped coefficient ) to the characteristics of the fiber grating (such as the reflectivity coefficient, time-delay character, dispersion and compression characters ) are analyzed. The results are used to design the Yb3+-doped ultrafast fiber laser. An all fiber loop-cavity with chirped fiber grating is brought forward. Comparing with the other structures of the non-all-fiber lasers, the structure we designed is more simple and has less loss.7. With ABCD matrix, the theory of the grating pairs using as the compression device is analyzed. The parameters of the grating pairs have been designed. As the facula of the fiber is small, a simple method using the single-pass grating pairs has been brought forward. The grating pairs have the virtue of the low price and good practicability.8. Amplification of the mode-locked pulse has been realized using the...
|
PDF Full Text Request