Experimental And Theoretical Studies On Ultrashort Pulse Lasers

Aiming at the ultrashort pulse laser systems, we study the generation and evolution of femtosecond pulses in detail both experimentally and theoretically. First, the laser cavity used in our experiment is calculated by using the ABCD laws. As a result, the stable regions and the relative spot size variation of the laser cavity have been obtained. Base on these results, we find the best astigmatically compensated angle and the favorite cavity parameters, which is beneficial to the generation of mode-locked pulses. The continuous-wave tunable and Kerr-lens mode-locked Cr⁴⁺:YAG lasers have been established experimentally and some valuable results have been obtained. Furthermore, we present a theoretical model of passively mode-locking lasers by using the high-order modified complex Ginzburg-Landau equation (CGLE) and find its exact solution. The solution's existing region and its stability have also been analyzed by using numerical method and variational method, respectively. At last, the effect of third-order dispersion on the novel solutions of the cubic-quintic CGLE and the interactions between two adjacent solitons are analyzed briefly. The main results of this thesis are as follows:1) Making use of the ABCD matrix law, the cavity of Cr⁴⁺:YAG laser is calculated. Then we obtain the astigmatically compensated angle and the best mode-matching conditions. After that, the characteristics of continuous-wave tunable Cr⁴⁺:YAG laser have been studied in experiments and more than 580mw continuous-wave power is obtained. By using one prism as a tunable element, we have obtained the tunable range of 160nm, which is tunable continuously between 1400nm and 1560nm.2) The Kerr-lens mode-locking parameter 8, which is important in KLM lasers, and the relationship between δ and cavity parameters have been analyzed by using nonlinear ABCD matrix. When the cavity's positive dispersion is compensated by two prisms and a semiconductor saturable absorber mirror is used to start the mode-locking, the mode-locked spectrum width of 37nm has been obtained and the center wavelength is 1520nm. If the transform-limited pulse is assumed, the...