The research work primarily concludes as follows : 1 . the steady rate equations are get under the analysis of four energy class of yb3 + , and the approximate resolution is carried out 研究工作主要包括: 1 、分析了镱离子工作的四能级系统,在近似求解稳态速率方程组的基础上得出了光纤激光器输出功率的解析表达式,并且计算了解析解与数值解的偏差。
First , we study electromagnetically induced absorption . this significant feature of the system model is that a four - level system in which three - dipole transitions are in n configuration in this system , the middle transition serves as a probe transition and two other transitions serve as couple transitions 系统的模型特征是：三个电偶极跃迁构成n型链的四能级系统，其中，中间跃迁为探测跃迁，两边的跃迁为耦合跃迁。
A theoretical study of input and output properties of four - level solid laser was performed according to the velocity equation , and the important role of the overlap integral j , was noticed and made a fully usage in optimizing the end - pumping solid state laser parameters such as : rod length > pump position pumping and oscillating beam waist size 从四能级速率方程出发，理论推导了ld端面泵浦的固体激光器的输入输出特性，并指出重叠积分j _ 1对激光器输出特性的极大影响，从而对其在不同泵浦条件下进行分析并以此得到端面泵浦条件下固体激光器的最优化设计参数的选取方法。
According to the guidline , two nd : yag lasers have been designed and set up , one is end - pumped by lower output power ld using a selfoc micro lens , and the other is end - pumped by high output power ld using a pair of lenses are designed , and the characteristics such as output power and power stabilization of both solid - state lasers are investigated . thirdly , when an empty liquid crystal cell is inserted in the cavity of the nd : yag laser pumped by high power ld , the laser can operates in single axial mode . finally , according to the relationship between the laser output power and the longnitudinal a ld - end - pumped nd : yag laser sensor for displacement measurement has been investigated theoretically and demonstrated experimently , the results indicate that when the mean radius of pumping inside the laser cavity is far less than that of the oscilating laser mode , the exponential of the output power is a gauss function of the longitudinal positon of focused spot of ld pumping beam , both the measurement range and the sensitivity are dependent on the incident pumping power , as the incident pumping power is increased , the measurement range is enlarged and the sensitivity is improve d 本文首先介绍了ld泵浦nd ： yag激光器的发展状况、主要特性及其应用，从四能级速率方程出发，推导了ld泵浦nd ： yag激光器的阈值、输出功率和斜效率的表达式，并简述了激光器的工作原理、结构型式和倍频方法；其次，以空间相关的速率方程为基础，提出了ld端面泵浦nd ： yag激光器的设计方法，给出了一定泵浦耦合方式下，振荡光模尺寸、最佳输出耦合率、泵浦光模尺寸、泵浦光焦斑位置等参数的选取依据，以此为依据，设计了自聚焦透镜耦合小功率ld泵浦nd ： yag激光器和透镜组耦合高功率ld泵浦nd ： yag激光器，对激光器的输出功率和功率稳定性等特性进行了实验研究；再次，在带尾纤输出的高功率ld泵浦nd ： yag激光腔内插入一只空液晶盒，观察到了激光器以单纵模运转；最后，根据泵浦光焦斑端面位置对激光输出功率的影响规律，提出了ld端面泵浦nd ： yag激光位移传感新方法，并进行了理论和实验研究，研究结果表明：当激光晶体内泵浦光平均光斑半径远小于振西安理工大学硕士学位论文荡光束腰半径时，激光输出功率的自然指数与泵浦光焦斑的纵向位置成高斯变化规律，测量范围和灵敏度依赖于泵浦功率，随着泵浦功率的增加，测量范围扩大，灵敏度提高，当端面泵浦功率为7 . 24w (最大输出功率为1 . 926w )时，激光位移传感器的测量范围和灵敏度分别是13 . 045mm和0 . 148mw / pm 。
In the second chapter , the operating principle of solid - state laser is analyzed . based on the model of four - level system , the interacting theory between laser field and laser crystal is studied by the rate equation theory , then the characters , such as threshold power , output power , slope efficiency etc . , of solid - state laser are deduced 第二章分析了固体激光器的工作原理，以四能级系统为模型，应用速率方程理论研究了激光场与激光晶体之间相互作用理论，导出了固体激光器的阈值功率、输出功率和斜效率等特性。
So lead to their polarization behavior not as good as edge lasers . the paper researched the polarization of vcsel theoretically and experimentally , the main work is as follows : part . without consideration the applied strain and temperature , we resolved numerically the maxwell - bloch equation through four - energy level polarized dynamic model 通过四能级偏振动力学模型，在不考虑外加应变以及温度的前提下，对maxwell - bloch方程进行数值求解，研究了随着注入电流以及各向异性的变化引起的vcsel的出射偏振光的强度、频率和相位变化。
We analyze the influences of the perturbed energy - level space and superposion , laser power and intermediate level offset on quantum interference . experimentally , in the sodium dimmer rhomb - type four - level system with a pair of perturbed levels , the interference enhancement of two - photon absorption caused by coherent superposition of the perturbed levels is experimentally observed 分析了微扰能级的间隔和叠加程度、激光功率以及中间能级的失谐对量子干涉效应的影响，实验上观察了包含有一对微扰叠加中间能级的菱形四能级系统中的双光子激发现象，发现微扰能级的相干叠加可增强双光子吸收。
Abstract : we have studied theoretically a beat effect in a four - level system due to fifth - order optical polarization , and considered the cases that the pump beams have either narrowband or broadband linewidth . we have found that the accuracy for the energy - level splitting measurement is determined by the homogeneous linewidths of the optical transitions . that is to say , this technique can achieve doppler - free precision in the measurement of the energy level splitting between two excited states which are dipolar forbidden from the ground state 文摘:研究了四能级系统中基于五阶极化的拍频效应，考虑了抽运光束为窄带线宽或宽带线宽的情形.发现其对能级分裂的测量精度决定于光学跃迁的均匀增宽.也就是说，这种技术在测量与基态是偶极禁戒跃迁的两激发态之间的能级分裂时，可得到消除多普勒增宽的精度
First , some principle that should be considered in building a laser cavity was discussed based on the rate equation of four - level laser model . then , the thermal lens effect of nd : yvo4 crystal was analyzed and estimated theoretically . the laser cavity was designed by considering the thermal lens effect and the optimal transmission was estimated 首先在理论上通过四能级激光器速率方程，讨论了激光器设计上需要注意的一些原则，然后分析了nd ： yvo _ 4晶体的热透镜效应，理论上估算了其热焦距的大小，并且在腔型设计中给予了考虑。
