【作者】 左春华；

【导师】 何京良；

【作者基本信息】 山东大学 ， 凝聚态物理， 2009， 博士

【摘要】 随着激光技术的不断发展,激光在医疗、军事、工业、科学研究以及日常生活中的应用越来越广泛。LD泵浦的全固态激光器由于结构简单、效率高、稳定性好等已成为目前激光器件的研究热点。激光晶体是全固态激光器的重要组成部分。本论文采用光纤耦合激光二极管作泵浦源,研究了Nd:GGG和Nd:CLTGG晶体的连续波激光运转;利用声光开关、饱和吸收体Cr⁴⁺:YAG、Co²⁺:LMA和V3⁺:YAG等晶体分别作为腔内调制元件,研究了Nd:GGG晶体1062nm和1331nm的主动、被动调Q和调Q锁模激光的脉冲输出特性;利用KTP和LBO晶体作为腔内倍频元件研究了Nd:GGG晶体倍频绿光和红光激光调Q运转特性;对调Q及调Q锁模激光的运转特性进行了理论模拟。具体内容如下:（1）系统总结了Nd:GGG晶体的物理、化学、力学等基本性质以及光谱特性、荧光光谱、吸收光谱、荧光寿命和发射截面等光学特性。对端面泵浦Nd:GGG晶体热焦距、固有损耗和热致损耗进行了实验测量,并从理论上进行了计算。实验结果和理论结果基本相符（第二章）。（2）对LD端面泵浦Nd:GGG晶体的1062nm、1331nm和938nm连续激光输出特性进行了研究。对于1062nm连续波激光器,能得到最大13.2W的连续激光输出,光-光转换效率为46.1%;对于1331nm连续输出激光器,最高输出功率为2.1W,相应的光-光转换效率为19%;对于938nm连续激光输出,得到了200mW的连续激光输出,光-光转换效率为2.3%（第三章）。（3）对Nd:GGG晶体1062nm的声光调Q激光运转特性进行了实验研究。获得的最大平均输出功率为2.34W,最大的脉冲能量和峰值功率分别为366μJ和12.9kW,对应的最短脉冲宽度为28ns;用V型腔研究了Nd:GGG晶体的1062nm的声光调Q锁模激光特性,得到的最大平均输出功率为3.32W,锁模效率最大为30.2%。并进行了理论模拟,理论值与实验值基本吻合。用V型腔研究了Nd:GGG晶体的声光调Q锁模倍频激光特性。得到最大绿光输出功率为660mW,倍频效率为27%。（§4.2,§4.3,§4.4）（4）用V型腔研究了Nd:GGG晶体的1331nm的声光调Q锁模激光特性。最大输出功率1.73W;调Q锁模转化效率为13.3%。同时,实验研究了Nd:GGG晶体声光调Q锁模1331nm LBO倍频红光,最大输出功率为378mW,获得最短脉宽为229ns;用KTP晶体倍频,获得最大红光输出功率为366mW,最短脉冲宽度为226ns。并分别进行了理论模拟,理论值与实验值基本吻合。（§4.5,§4.6）（5）用Cr⁴⁺:YAG晶体做饱和吸收体,对LD端面泵浦Nd:GGG晶体的被动调O激光特性进行了理论和实验研究。Cr⁴⁺:YAG晶体的小信号透过率为90%和85%时,得到了最大的调Q平均输出功率分别为2.87W和2.63W,而此时连续最大输出功率为3.39W,从连续到调Q的转化率分别达到了84.7%和77%。在小信号透过率为70%时,得到了最窄的脉冲4ns,相应的最大的单脉冲能量为206μJ,最大峰值功率为51.6kW。（§5.2）（6）用Co²⁺:LMA晶体做饱和吸收体,对Nd:GGG晶体的1331nm被动调Q激光特性进行了理论和实验研究。得到最大平均输出功率为183mW,对应的光光转化效率为5.6%,最短脉冲为16.4ns,最大单脉冲能量为21.4μJ。用V³⁺:YAG晶体被动调Q 1331nm激光,得到最大输出功率为460mW,光转换效率为5.6%。得到的最短脉冲为19ns,最大单脉冲能量为11.8gJ,峰值功率为0.65kW。（§5.3,§5.4）（7）Cr⁴⁺:YAG晶体作为饱和吸收体,对Nd:GGG晶体1062nm调Q锁模运转特性进行了实验研究。小信号透过率为85%时,锁模效率为15%,最大平均功率为1.38W,此时重复频率为27kHz,脉冲能量为51μJ。小信号透过率为76%时,锁模效率为10%,最大功率为0.7W,重复频率为11kHz,脉冲能量为65μJ,估算锁模脉宽为348ps。并进行了理论模拟,理论值与实验值基本吻合。（§6.2）（8）分别用Co²⁺:LMA和V³⁺:YAG晶体作为饱和吸收体,对Nd:GGG晶体1331nm被动调Q锁模激光特性进行了实验研究。Co²⁺:LMA小信号透过率为81%,锁模效率为1.4%,得到最大调Q锁模平均功率为103mW,最大调Q脉冲能量为8.4μJ。估算锁模脉宽为446ps。V³⁺:YAG晶体的小信号透过率为94%,得到了最大的调Q锁模平均功率为410mW,锁模效率为5.5%,最大脉冲能量为8.3μJ。估算锁模脉冲的宽度约为750ps。并进行了理论模拟,理论值与实验值基本吻合。（§6.3,§6.4）（9）总结了石榴石无序结构晶体Nd:CLTGG的物理性质和光谱特性,实验研究了Nd:CLTGG晶体在1.06gm的连续和Cr⁴⁺:YAG被动调Q的激光特性。对于连续波激光运转,输出功率为1.32W,斜效率为17.1%。采用小信号透过率为95%的Cr⁴⁺:YAG作为被动调Q晶体,获得最大平均功率为91mW,光-光效率为2.8%,此时最短脉冲为16.3ns,重复频率为2.59kHz,脉冲能量和峰值功率分别是35.1μJ和2.16kW（第七章）。论文的主要创新工作包括:（1）首次对LD端面泵浦Nd:GGG晶体热焦距、固有损耗和热致损耗进行了实验测量,并从理论上进行了计算。（2）分别用直腔和V型腔研究了Nd:GGG晶体1062nm和1331nm声光调Q及声光调Q锁模的激光特性,并分别研究了它们的倍频激光特性。（3）分别利用Cr⁴⁺:YAG、Co²⁺:LMA和V³⁺:YAG晶体对Nd:GGG晶体进行被动调Q及被动调Q锁模1062nm和1331nm的激光运转特性进行了理论和实验研究。（4）总结了石榴石无序结构晶体Nd:CLTGG的物理性质和光谱特性,首次实现了Nd:CLTGG晶体在1.06gm的连续激光运转和Cr⁴⁺:YAG晶体被动调Q激光运转。更多还原

【Abstract】 With the development of the laser technique,lasers are widely used in fields of industry,medical treatment,military and our daily life.Diode pumped solid state lasers（DPSSL） have become the central focus of the field of lasers due to their many advantages such as compactness,high efficiency,high stability,etc.Laser crystal is an important part of laser system,in this dissertation,by using the fiber-coupled laser-diode as the pump source,Nd:GGG and Nd:CLTGG crystals as the gain mediums,we have studied the performance of the actively Q-switched lasers of 1062nm as well as 1331nm with acoustic-optic（AO） modulator,and passively Q-switched lasers with Cr⁴⁺:YAG,Co²⁺:LMA and V³⁺:YAG saturable absorbers, respectively.And we also have studied the performance of the diode-end-pumped Nd:GGG red and green laser by using frequency doubling crystals of KTP and LBO. In addition,by using Cr⁴⁺:YAG,Co²⁺:LMA and V³⁺:YAG as the intracavity mode-locker,respectively,the simultaneously Q-switched and mode-locked lasers have been realized.Meanwhile,the coupling rate equations under Gaussian distribution approximation have been used to theoretically analyze the properties of the above-mentioned Q-switched lasers as well as the simultaneously Q-switched and mode-locked lasers.The main content of this dissertation includes:（1）We have summarized the physical,chemical,mechanical and optical characteristics of the crystal of Nd:GGG.And we have measured the intrinsic loss,thermally induced loss and thermal focal length of the crystal.The experimental results were consisted with the calculated results.（Chapter 2）（2） We have demonstrated the diode-end-pumped Nd:GGG continuous lasers of 1062nm,1331nm and 938nm.（Chapter 3）（3） We have studied the performance of the actively Q-switched lasers of 1062nm.The maximum output power of 2.34W was obtained.The maximum pulse energy of 366μJ,the maximum peak power of 12.9kW,and the minimum pulse width of 28ns were obtained,respectively.We have studied the performance of the actively Q-switched mode-locked lasers of 1062nm.The maximum average output power of 2 3.32W was obtained,the conversion efficiency from CW to Q-switched mode locked was 30.2%.The mode locked pulse width was estimated to be 120ps.The experimental results were consisted with the calculated ones.（§4.2,§4.3）（4）We have studied the performance of the diode-end-pumped Nd:GGG green lasers by using frequency doubling crystal of KTP.The maximum average output power The maximum output power of 660mW was obtained,and the frequency doubling efficiency was 23.7%.We have studied the performance of the actively Q-switched mode locked lasers of 1331nm.The maximum average output power of 1.73W was obtained the conversion efficiency from cw to Q-switched mode locked was 13.3%. We have studied the performance of the diode-end-pumped Nd:GGG red lasers by using frequency doubling crystals of LBO.The maximum of average output power of 378mW of red laser was obtained.We also have studied the performance of the diode-end-pumped Nd:GGG red lasers by using frequency doubling crystals of KTP, the maximum average output power was 388mW,the minimum pulse width was 226ns,the maximum single pulse energy and the maximum peak power were 63.8μJ and 284W respectively.（§4.4,§4.5,§4.6）（5） By using Cr⁴⁺:YAG crystals as the saturable absorber,the Q-switched lasers of 1062nm have been realized.The maximum average output power 2.87W and 2.63W were recorded with initial transmission of 90%and 85%,corresponding to the conversion efficiency from CW to Q-switched of 84.7%and 77%,respectively.When the initial transmission was 70%,the minimum pulse width was recorded to 4ns,and the corresponding maximum single pulse energy and peak power were 206μJ and 51.6KW,respectively.（§5.2）（6） By using Co²⁺:LMA as the saturable absorber,the Q-switched lasers of 1331nm have been realized.A maximum average output power of 183 mW was recorded with a Co²⁺:LMA SA with initial transmission of 90%.By using a V³⁺:YAG crystal with initial transmission of 94%as the saturable absorber,the maximum average output power of 460 mW,the minimum pulse width of 19 ns and the repetition rate of 39 kHz were achieved,corresponding to pulse peak power of 0.62 kW and single pulse energy of 11.8μJ,respectively.（§5.3,§5.4）（7）By using Cr⁴⁺:YAG crystal as the saturable absorber,a diode-pumped passively Q-switched and mode-locked Nd:GGG laser operating at 1062nm was realized.The maximum output power of 1.38W and the Q-switched pulse energy of 51μJ were obtained when the initial transmission of Cr⁴⁺:YAG crystal was 85%。When initial transmission of Cr⁴⁺:YAG was 76%,the maximum average output power of 0.7W and the pulse energy of 65μJ were obtained.The space-dependent rate equations which describe the mode-locking process were solved numerically,the theoretical calculations reproduced the laser characteristics well.（§6.2）（8） By using Co²⁺:LMA crystal as the saturable absorber,a diode-pumped passively Q-switched and mode-locked Nd:GGG laser operating at 1.3μm was realized.The mode-locking modulation depth of nearly 100%has been achieved.The maximum output power of 103mW and the Q-switched pulse energy of 8.41μJ were obtained.By using V³⁺:YAG crystal as the saturable absorber,The maximum output power of 410mW and the Q-switched pulse energy of 8.3μJ were obtained.The theoretical calculations reproduced the laser characteristics well（§6.3,§6.4）（9） The diode-end-pumped Nd:CLTGG lasers have been studied.The absorption spectra, luminescence spectra and the luminescence life time of Nd:CLTGG crystal has been summarized.The maximum output power of CW laser of 1.32W was obtained for the first time.The solpe efficiency was17.1%.By using Cr⁴⁺:YAG crystal with initial transmission of 95%as the saturable absorber,the maximum average output power of 91mW was obtained,the minimum pulse width was 16.3ns,the single pulse energy and the peak power were 35.1μJ and 2.16kW respectively.（Chapter 7）The main innovations of this dissertation are as follows:（1） For the first time,we have measured the intrinsic loss,thermally induced loss and thermal focal length of the diode-end-pumped Nd:GGG crystal.The experimental results were consisted with the calculated results.（2） We have studied the performance of the actively Q-switched and actively Q-switched mode locked lasers at 1062nm and 1331nm.And studied the performance of the diode-end-pumped Nd:GGG red and green lasers by using frequency doubling crystals of KTP and LBO.（3） By using Cr⁴⁺:YAG,Co²⁺:LMA and V³⁺:YAG crystals as the saturable absorbers,the diode-pumped passively Q-switched and mode-locked Nd:GGG laser operating at 1062nm and 1331nm were realized for the first time.（4） For the first time,the diode-end-pumped Nd:CLTGG lasers has been studied,and by using Cr⁴⁺:YAG crystal as the saturable absorbers,a diode-pumped passively Q-switched Nd:CLTGG laser operating at 1.06μm was realized for the first time.更多还原