Study On The Frontier Techniques Of Kerr Lens Mode Locked Ti: Sapphire Laser

The operation characteristics of Kerr lens mode locked Ti:sapphire lasers is theoretically and experimentally studied in detail in this dissertation. The self-starting of Kerr lens mode locked lasers and the effect of SESAM's negative Kerr effect on the starting process of the lasers is theoretically analyzed by linear and nonlinear ABCD matrix law and the small signal spot size variation. Supercontinuum generation from a femtosecond Ti:sapphire oscillator is experimentally demonstrated.The results are described as follows:1. The five-mirror laser cavity containing a SESAM with negative Kerr effect is theoretically analyzed for the first time. It shows that, compared with the cavity without a SESAM, the up stable range of the resonator expands obviously after the introduction of SESAM. This indicates that the operating point for self-starting can be closer to the edge of the stable range of the CW state, and then get higher nonlinear effect. These reveal that the negative Kerr effect of the SESAM can contribute to the self-starting of mode-locked lasers besides the saturable absorption mechanism.2. Base on the principle of Kerr lens mode locking and the fact that the coupling between the laser and pump in the crystal varies with the power, the absorber-like equation is derived. The self-starting condition expressed by the small signal spot size variation is demonstrated, according to the passive absorber-like self-starting condition.3. The starting characteristics are theoretically analyzed according to the self-starting condition of Kerr lens mode locking. The results show that the symmetrical resonator can obtain the highest effective nonlinearity. And the effective nonlinearity can be improved by adjusting the resonator's arm length or the radius curvature of the cavity mirror.4. A new Kerr-lens mode-locked resonator that is easily self-starting and highly stable is presented. It is theoretically demonstrated that the effective nonlinearity increases dramatically after the introduction of a spherical mirror with large radius curvature to one arm of the usually used four-mirror cavity. This will make the mode locking of the lasers easier and more stable.5. An octave-spanning continuum ranging from 460nm to 1000nm from a self-Q...