The Characteristics Of LD End-pumped Laser Crystal On Thermal Effect And Second Harmonic Generation

Diode-pumped all-solid-state lasers(DPSL) has lots of advantages,such as compact structure, high stability and optical-optical conversion efficiency. It is widely used in national defence, photoelectron industry, communication, medical treatment and sanitation. Laser crystal is the core of diode-pumped all-solid-state lasers, which decide the output characteristics of laser. In recent years, in endeavoring to obtain higher output powers from continuous-wave end-pumped solid-state lasers, one must consider thermal effects that will impact optical performance. In all the laser crystal which is suitable for DPSL, Nd:YVO₄ and Nd:GdYVO₄ are widely used for its excellent physical and chemical laser characteristics. In our paper, Nd:YVO₄-KTP green light laser ,Nd:GdYVO₄-KTP green light laser and Nd:YAG-LBO blue light laser is introduced. The thermal effect of circular-face Nd:YAG, rectangular-face Nd:YVO₄ and Nd:GdYVO₄ has been calculated. The contents can be outlined as follows:1. The history and progress of diode-pumped solid-state lasers are reviewed; and the characters of the diode-end-pumped solid-state laser are presented; then the dissertation presents the crystals of fitting diode-end-pumped.2. The thermal effect theory of circular-face laser crystal was analysed. By using this theory, the temperature distribution in laser crystal was obstained. The study shows that in the same condition when the Nd ion concentration increase, the central temperature of Nd:YAG crystal's pumped face will rise and the temperature of crystal central axis will reduce faster. For the same ctystal, when the pumping radius decrease, the central temperature of Nd:YAG crystal will rise. Then the temperature fields distribution of end-pumped Nd:YVO₄, Nd:GdVO₄ and Nd:GdYVO₄ were obtained by solving Possion equation numerically. The thermal distortion field of pump-face are obtained. The thermal effect of Nd:YVO₄, Nd:GdVO₄ and Nd:GdYVO₄ by high power eccentric-end pumped was investigated also.3. The speed-rate equations was introduced , the relationship between output power and input power under CW pumped condition and pulse pumped condition was obtained. The three wave interaction theory and normal phase match theory was introduced. The solution of second harmonic generation in type-Ⅰand type-Ⅱphase-match is obtained.4. The history and progress of diode-pumped solid-state green light lasers and the characteristics of Nd:YVO₄, Nd:GdYVO₄ was introduced. Under the same experimental conditions, we use plane-plane cavity to compare the fundamental frequency with CW pumped and pulse pumped. With the CW pumped power of 10.64W, an output power 6.29W and 5.35W was achieved. Under the pulse pumped condition, the relationship between output power and input power with different T is obtained. And the comparison of Nd:YVO₄ and Nd:GdYVO₄(T=10%) is obtained. The comparison of the same crystal under CW operation and pulse operation is obtained, too.Using ABCD matrix , we choose V-shaped cavity which compress the radius of pump beam on KTP efficiently. With the pumped power of 6.71W, an output power 2.34W and 1.73W of stable frequency-doubled green light was achieved by v-shaped folded cavity. From the theory in Chapter 3, we get the relationship of input and output in theory, compared it with the experimental result, discovered the experimental results almost coincided with the theoretical results.5. The history and progress of diode-pumped solid-state blue light lasers was introduced. Using plane- concave cavity, the blue light was obtained by Nd:YAG-LBO. From the experiment, with the pumped power of 7.33W, an output power 131.4mW was achieved. Based on the real experiment condition and the theory introduced in Chapter 2 , the thermal effect of Nd:YAG is analysed.