LD Side-pumped Actively Q-switched And Passively Mode-locked Laser

Along with the emergence of new types of crystals, ultrafast solid-state lasers have the rapid development. Compared with ultrafast fiber lasers, ultrafast solid state lasers have higher peak power, better beam quality, higher signal to noise ratio. In the 1990’s, the appearance of semiconductor saturable absorption mirror (SESAM) made ultrafast solid-state lasers have undergone major changes. Based on SESAM mode-locked mechanism, a variety of solid-state lasers spring up, and their structure, indicators and performance improve continuously, and the mode-locked lasers with SESAM have appeared. However, the price of fiber-coupled semiconductor laser pumping source is high, at the same time, the output power is not enough high. So, in the thesis, we research on LD side-pumped mode-locked and Q-switched laser, and expect to achieve ultrafast solid-state laser source with high power.In this thesis, LD side-pumped actively Q-switched laser and passively mode-locked laser are researched in detail. The acousto-optically Q-switcher and KTP crystal are used to achieve Q-switched green pulse, and the output power is about 9W,and the frequency doubling efficiency reached 46.1%. We have studied Nd:YAG passively mode-locked laser with in-house SESAM based on theories and experiments. The ps continuous wavelength mode-locked pulse in linear cavity and Z-type cavity are both obtained. The main work is as following:1. The theory of acousto-optic Q-switching and passively mode-locking are described, and some key factors for mode-locking are provided.2. Considering the thermal effect of LD side-pumping module, the parallel light detection method and the critical stable resonator method are used for measuring thermal lens focal length.Compared from each aspect of them, a better method is chosen.3. The two most typical types, linear cavity and Z-type cavity, are analyzed by ABCD transfer matrix method, and the experimental study for them are done. The best cavity structures for the Q-switched laser and mode-locked laser are proposed.4. The experimental setup of the LD side-pumped Q-switched laser is designed and optimized. The acousto-optic Q-switcher is used for the experiment. From the experiment, the Q-switched pulse width of about 140ns and the power of 10W is achieved. When frequency doubling crystal KTP is inserted in the cavity, the Q-switched green pulse with about 146ns pulse width and 8.86W output power is achieved and the doubling efficiency reaches 46.1%.5. The experimental setup of the LD side-pumped mode-locked laser is designed and optimized. Mode-locking experiments with linear cavity and Z-type cavity are done. The wavelength of 1064nm, the average power of 2W, the repetition frequency of 245MHZ, and the pulse width of 121.5ps continuous mode-locked picosecond laser is achieved in linear cavity. The average power of 1.2W, the repetition frequency of 105MHZ, the beam quality factor M2 of about 1.2 and the pulse width of 23.4ps continuous mode-locked picosecond laser is achieved in Z-type cavity. At the same time, the mode-locked pulse which is modulated with an acousto-optic Q-switcher and a SESAM is obtained and the stability of mode-locked pulse is improved, at the same time, the single pulse energy for mode-locked laser is improved from 10nJ to 17μJ.