Ld Side-pumped High-power Green Laser Research

With the development and maturity of high power laser diode, LD pumped all-solid-state laser has become an international hot research topic in laser technology. Nonlinear optical frequency conversion technique has further expanded the applications of DPL(Diode pumped laser). LD pumped green laser, with its compactness, high efficiency, long lifetime and good beam quality, has been widely used in laser display, industrial process, scientific research and medical treatment. Under this background, theoretical and experimental research has been made on high power LD side-pumped intra-cavity frequency-doubled green laser in the dissertation. The main points can be summarized as follows:1. The development and characteristics of LD-pumped all-solid-state laser are introduced at the beginning. Then the broad applications of all-solid-state green laser are presented and the progresses of high-power LD-pumped green laser are summarized.2. After detailed analysis of the characteristics of Nd:YAG crystal, the temperature distribution within the Nd:YAG rod side-pumped by LD arrays and the resulting thermal lensing are calculated. Then methods for reducing and compensating thermal focal length are summarized. Based on ABCD matrix, the stability condition and beam feature in the resonator are simulated and analyzed.3. Rate equation of four-level laser system are analyzed and the continuous operation characteristics of all-solid-state laser are investigated. Then experimental study by using concave end and grooved rod is made respectively and has laid solid ground for the frequency-doubled 532nm green laser experiments.4. Starting with nonlinear coupled-wave equation, the theory of second harmonic generation is given detailed analysis. Two commonly used frequency doubling cystal, KTP and LBO are comparatively studied. Then two different ways of obtaining second harmonic generation by placing the frequency doubling cystal either in or outside the resonator are discussed.5. Based on theoretical analysis of the acoustic Q-switched intra-cavity frequency doubled green laser system, experimental study on high power qusi-cw all-solid-state green laser are made with single Q switch and dual Q switches. Finally, with single grooved Nd:YAG rod, dual orthogonal placed Q switches, typeⅡcritical phase matched KTP in a plano-plano resonator, a maximum of 197.5W average power 532nm laser ouput was achieved at pumping current of 14A, repetition rate of 38.7kHz, corresponding to a frequency doubling efficiency of 42%.