LD泵浦的全固体绿激光器研究

Study on Diode-pumped solid Green Laser

主要论述了用激光二级管（ＬＤ）泵浦、内腔倍频的绿激光器的原理和结构。在激光阈值、斜效率的讨论中指出：当ＬＤ的泵浦光束在激光晶体中的尺寸越小，光功率密度越高，激光阈值就越低，转换效率就越高；在放大基波的结构中，激光腔镜对基波的反射度越高，基波的放大倍数就越大，转换效率就越高；重点讨论了内腔倍频激光器中的“绿光问题”，指出造成“绿光问题”是由于模式正交分量之间的和频效应与空间烧孔形成的横向饱和；用Ｐｏｉｎｃａｒｅ图分析了激光器中出现的混沌行为；对如何克服“绿光问题”，得到稳定激光输出提出了几种方案。针对ＬＤ的光形状是一个椭圆光锥，选择了用多组透镜准直、棱镜对扩束的泵浦光传输系统方案；对腔体、激光膜层作了概述，具体提出了用平凹腔结构，并把激光膜层直接做在晶体上，可以减少腔内损耗；对ＹＡＧ－ＫＴＰ，ＹＶＯ＿４－ＫＴＰ组合的绿激光器作了研究。在内腔倍频ＹＡＧ激光器中观察到的实验现象很好地附合理论结果。在ＹＶＯ＿４－ＫＴＰ的绿激光器中，比内腔倍频ＹＡＧ激光器较容易得到ＹＡＧ－ＫＴＰ组合绿激光器，最大连续输出功率为１４．４ｍＷ，阈值１５．０ｍＷ，光－光斜效率为４．１％。ＹＶＯ＿２－ＫＴＰ绿激光器：最大连续输出１２０ｍＷ，?

Theory and structure of intracavity doubling,diode-pumped graeen laser are discussed.the former is theory. First ,the laser threshold and slope efficiency are discussed.when beamof laser diode pumped is smaller in laser crystal,optical density is higher, laser threshold islower and slope efficiency is higher;Second,mechanism with intracavity to enhance IR-Green conversion efficiency is analyzed.In fundamental enhanced mode,the higher mirror re-flected to fundamental wave is,the bigger multiplicity of fundamental wave and the higherconversion efficiency are. Third,″Green Problem″in intracavity doubling Nd:YAG laser isanalyzed.Intracavity doubling Nd:YAG exhibit amplitude fluctuations driven by a combina-tion of sum frequency between orthogonally polarized modes and nonlinear cross saturationproperties beacause of spatial hole burning. The Poincare map is used to diagrammatized chaos behavior in green laser. Some schemes how to overcome″Green Problem″and to obtainstable green light output are designed finally. The latter is laser designed . First,because emission distribution is a ellipsoid cone,a transmission system of LD beam is designed specially. Second, In order to reduce loss in cavity,a plano-convex cavity on which mirror is deposited directly is determined.YAG-KPT and YVO_4-KTP green laser are studied at last.Single transverse mode is easier to gain in YVO_4-KTP green laser than that of YAG-KTPlaser. Specifications:YAG-KTP,threshold :l5.0mW; high output power:14.4mW ;slopeefficiency:4.1%,wavelength:532nm;YVO_4-KTP,threshold:l00mW,high output power:120mW,slope efficiency:6.3%,wavelength:532nm.