光束

In recent years, beam-shaping methods are rapidly developed which include beam collimating, beam-shaping and beam focusing.

近几年发展起来的一种耦合方案是整形耦合法，其包括光束准直、光束整形、光束聚焦三部分。

Thus by using longer crystal and focused pump beam in OPA or OPO, the gain of amplification can be increased and oscillation threshold be reduced.

本文从理论上和实验上证实，OBNC对OPA和OPO参量作用有特别重要的意义，它可以使泵光束和信号光束在非线性晶体中实现最大的交叠并允许泵光束有较大的发散度，从而可以通过加长非线性晶体的长度或会聚泵光以增加参量作用的增益和降低振荡的阈值。

The lens axicon is based on the use of the spherical aberration of the mirror surfaces,which is inexpensive and easy to manufacture into a element with large apertures as compared with diffractive axicons,refractive cone axicons,and earlier lens axicons with aspheric surfaces;the opaque disk can offer the Bessel beams with long non-diffracting distances,and the diameter of the central peak is adjusted by choosing the focal length of the collimating lens;the tunable fluidic conical lens is a new device for generating Bessel beams,which can obtain the Bessel beams with different parameters by varying the refractive indexes of the solution which is filled in the device.

双透镜轴棱锥法主要基于透镜球面像差的运用，与衍射轴棱锥、折射轴棱锥和早期的非球面轴棱锥相比，具有加工简单、便宜，易于制作大尺寸的特点；不透明障碍物法得到的贝塞尔光束具有很长的无衍射距离，其直径可通过选择不同焦距的准直透镜来得到调节；可调流体轴棱锥是一种产生贝塞尔光束的新型器件，它可以很容易地通过改变注入器件的液体的折射率来得到不同参量的贝塞尔光束。

It is found that the changes resulted from the inclination of the moving mirror consists of three parts: the stationary OPD due to the optical beam deflection,the offset OPD due to the different ray in the direction perpendicular to the optical axis,and the offset from the center of the deflected beam to the optical axis.

结果表明，光束偏转带来的误差分为三部分：光束偏转导致整体增加的恒定光程差，垂直光轴方向因不同光线而引入的偏移光程差以及偏转光束中心相对于光轴的偏移量。

Firstly,the effect of aberrationsof the optical system on Gaussian beams whose incident position does not coincide with thecenter of the pupil for the aberrated optical system has been analyzed,then we evaluate theStrehl ratio of the beams as a function of their incident position and the kind of aberrationspresented in the optical system.

首先，得到了初级和次级光学像差函数在光束坐标系中的表达式，继而给出了特定像差系统的Strehl比，并通过计算机模拟，得到了系统的SD值与光束入射位置和光束半径的关系曲线图。

In this dissertation, based on the beam propagation equation in the free-space, the hyperbolic-fit mothed is used to calculate the M2- factor of Gaussian beams passing through a spherically aberrated lens for the first time.

本论文根据自由空间中光束的传输方程，利用多点拟合的方法，通过数值计算，首次研究了激光束通过球差透镜后的M~2因子随球差的变化规律，并用M~2因子、桶中功率和K参数作为光束质量评价参数，讨论了透镜的像差、遮拦比等对激光光束质量的影响。

This problem is also important and valuable in Nonlinear Optics. It will be very helpful to understand how the aberrations affect the course of three- wave mixing, such as the change of conversion efficiency, the distribution of intensity and phase.Small signal solution of aberrated second harmonic generation is deduced from three-dimension three wave coupling functions. The numerical work gives out lot of results of different aberrations. The effects of the fundamental waves aberrations, which will change the conversion efficiency, distribution of intensity and phase in the frequency conversion, is analyzed. It shows that when walk-off and diffraction effects could be ignored approximately estimation of the phase distribution of second-harmonic wave could be done. The far field divergent angle and second moment radius of harmonic wave will vary with the aberration of fundamental wave, but the far field divergent angle will be obviously smaller than that of fundamental wave. The phase distribution of both fundamental and harmonic wave is measured using Hartmann-Shack wave front sensor in the experiment with 1064nm and 790nm lasers, respectively. Results are given.

首次从三维三波相互作用方程组推导得到了位相畸变光束倍频的小信号解；通过建立国防科学技术人学研究生院学位论文三维数值模型，编写相应仿真程序，首次得到了位相畸变光束倍频过程的大量计算结果，深入细致地研究了位相畸变光束经非线性光学频率变换后谐波的转换效率、光强分布、位相分布以及影响它们的各种因素；得出谐波的远场发散角和光斑二阶矩的变化规律会因为基波像差的不同而不同，但谐波的远场发散角明显地比相应基波的小的结论；得到了在走离效应和衍射效应等影响许多因素可以忽略的情况下，位相畸变传递到二次谐波的估算式；举例分析了KDP三倍频方案中，基波位相畸变对二次谐波和三次谐波的影响；实验工作中，用哈特曼一夏克传感器分别对IO64nm倍频过程和790飞秒超短脉冲倍频过程中的基波和谐波的位相分布进行了测量，给出了相应结果。

Small signal solution of aberrated second harmonic generation is deduced from three-dimension three wave coupling functions. The numerical work gives out lot of results of different aberrations. The effects of the fundamental wave's aberrations, which will change the conversion efficiency, distribution of intensity and phase in the frequency conversion, is analyzed. It shows that when walk-off and diffraction effects could be ignored approximately estimation of the phase distribution of second-harmonic wave could be done. The far field divergent angle and second moment radius of harmonic wave will vary with the aberration of fundamental wave, but the far field divergent angle will be obviously smaller than that of fundamental wave. The phase distribution of both fundamental and harmonic wave is measured using Hartmann-Shack wave front sensor in the experiment with 1064nm and 790nm lasers, respectively. Results are given.

首次从三维三波相互作用方程组推导得到了位相畸变光束倍频的小信号解；通过建立三维数值模型，编写相应仿真程序，首次得到了位相畸变光束倍频过程的大量计算结果，深入细致地研究了位相畸变光束经非线性光学频率变换后谐波的转换效率、光强分布、位相分布以及影响它们的各种因素；得出谐波的远场发散角和光斑二阶矩的变化规律会因为基波像差的不同而不同，但谐波的远场发散角明显地比相应基波的小的结论；得到了在走离效应和衍射效应等影响许多因素可以忽略的情况下，位相畸变传递到二次谐波的估算式；举例分析了KDP三倍频方案中，基波位相畸变对二次谐波和三次谐波的影响；实验工作中，用哈特曼-夏克传感器分别对1064nm倍频过程和790飞秒超短脉冲倍频过程中的基波和谐波的位相分布进行了测量，给出了相应结果。

Nonlinear self-focusing of ripple can effect on far field in high energy too.

基于这些特点，理论分析了影响光束远场的因素以及在高通量下噪声纹波的非线性自聚焦效应，模拟了具有四程放大结构的高功率激光装置的传输特性，分别研究了注入光束振幅和光学元件引入的相位噪声对光束远场的影响。

Furthermore,the beam quality on far field is discussed.Temperature rise,thermal deformation,wavefront distortion and beam quality of fused quartz(SiO_2) window and white bijou(Al_2O_3) window irradiated by the annulus beam are simulated as examples.

以空心环形光束为例，计算了熔融石英(SiO2)和白宝石(Al2O3)两种常用窗口的温升分布、热变形、波前相差和光束质量，分析了冷却、辐照时间、光强分布的空间梯度和各种材料参数对光束质量的影响。

With Death guitarist Schuldiner adopting vocal duties, the band made a major impact on the scene.

随着死亡的吉他手Schuldiner接受主唱的职务，乐队在现实中树立了重要的影响。

But he could still end up breakfasting on Swiss-government issue muesli because all six are accused of nicking around 45 million pounds they should have paid to FIFA.

不过他最后仍有可能沦为瑞士政府&议事餐桌&上的一道早餐，因为这所有六个人都被指控把本应支付给国际足联的大约4500万英镑骗了个精光。