线激光束均匀化整形方法研究

为解决核物理工程、表面热处理、激光加工、激光通信中传输激光束的均匀性问题,提出采用三角楔柱透镜改善线激光均匀性的新方法,并在ZEMAX开发环境下建立了整形光路系统的理论模型。利用所建立的模型,分析了整形柱透镜在不同半径、斜面夹角、透镜介质折射率等参数下光束的均匀性。研究表明：在远场条件下,通过改变整形柱透镜的参数,能够得到能量分布均匀的线激光。在实际应用中,可以采用1个半圆柱和2个相同三角楔胶合成型的简单工艺。进一步模拟发现,两种整形系统所得到的均匀度和线宽一致。     

柱面透镜准直LD光场的计算建模方法研究

为了简化LD光场准直柱面透镜繁琐的理论设计过程,便于进行实际操作,利用Matlab计算建模的方法,计算理想准直柱面透镜上的各个离散点的坐标值,通过拟合或二次曲面方程逼近的方法来获得准直柱面透镜的面型参数。分析表明,二次曲面柱面透镜非常适合做半导体激光器的准直透镜,可以根据具体需要来选择相应的面型。相比于其他方法,该方法简单直观,易于设计和加工,参数的优化调整迅速,可以根据加工工艺的难易程度来选择合理的透镜参数。     

激光辐照猫眼光学镜头时的反射特性机理研究

运用矩阵光学理论以及将硬边光阑窗口函数展开为有限个复高斯函数之和的方法, 对激光束辐照猫眼光学镜头时产生的猫眼效应机理进行了理论推导. 通过数值计算对猫眼效应的反射规律进行了分析, 并利用532nm激光辐照一个变焦范围为12—72mm的光学镜头进行了猫眼效应的实验验证, 从而得出了猫眼效应反射光特性与入射激光参数以及猫眼光学镜头的口径、焦距、离焦量等基本参数之间的关系. 研究表明, 猫眼效应反射光特性与猫眼光学镜头参数和入射激光参数密切相关, 且当猫眼光学镜头位于近场和远场的情况有很大不同. 根据入射光束 关键词： 猫眼光学镜头 猫眼效应 高斯光束 反射特性     

Automatic compensation of laser beam focusing parameters for flying optics

Flying optics technologies are used for a range of applications such as a large workpiece processing and laser texturing. It is essential to compensate the variations of laser beam focus parameters while the focus head is moving. A flying optics automatic compensation approach is proposed to achieve invariable laser focal size, focus depth and focus position through computer controlled objective lens and focus lens position. A simple mechanical control method is also presented for the realization of constant beam parameters for flying optics. Numerical simulation is illustrated for a CO₂ laser texturing application. The flying optics parameters compensation is simple and easy to control.     

Error propagation in laser beam spatial parameters

We have performed a propagation-of-errors analysis on two methods used to determine the spatial parameters of a laser beam. We measured diameters of a diode laser beam focused by a 993 mm focal length lens. Measurement uncertainties of less than 1% can result in uncertainties greater than 200% in locating the beam waist of the laser. We compare the inherent uncertainties in the spatial parameters as obtained by the two methods. Longer focal length lenses and lens position can reduce this magnification of uncertainty, but would require large propagation distances.     

Thermal lens and its effects in copper-vapor lasers

We have analyzed and measured the thermal lens of the copper-vapor laser by considering both its windows and active medium. The equivalent combined focal length varies with operation parameters and it is sensitive to the laser geometry. The results are verified by our measurements on a 20 W device with 35 mm internal diameter tube. The thermal lens effects on the beam properties are analyzed and verified with the experiments for both oscillator and laser chain case.     

Efficient design considerations for end-pumped solid-state-lasers

The temperature distribution in the gain medium and key design parameters for an ideal-four level end-pumped solid-state laser have been analyzed depending on the crystal's length, absorption coefficient, and pump beam M² factor. The optimum key design parameters and thermal focal lens are obtained by minimizing the root mean square of pump beam radius in the laser crystal. It is found that the focal thermal lens and key design parameters are dependent on the gain medium characteristics and pump beam properties as well. By considering the Poisson equation in cylindrical coordinate and Top-Hat pumping profile, an analytical formula has been derived to introduce the thermal focal length in the end-pumped lasers. A formula is also presented to relate the requirements of pump source to the gain medium properties for working laser at the design point.     

飞行光学导光系统中的空气热透镜效应

研究了激光加工用大功率ＣＯ２激光束在飞行光学导光系统中传输所产生的空气热透镜效应。实验发现当飞行光学导光系统中的空气静止时将产生空气热透镜效应,而充以一定压力的压缩空气却可以消除空气热透镜效应,实验表明无热透镜效应时,光束遵循高斯光束传输规律,而秀热透镜效应时,光束偏离高斯光束的传输规律,并影响到激光束聚焦焦点的大小和位置。另外通过激光空气热透镜效应的非线性模型计算了热透镜效应所引起的光束传输相对     

离散效应对高强度激光三次谐波转换的影响

使用分步傅里叶变换和四阶龙格库塔法(R-K) ，对高强度激光以Ⅰ/Ⅱ类角度失谐方式，在KDP晶体中的谐波转换进行了研究，详细讨论了离散效应对三次谐波转换的影响。结果表明，离散效应不但降低了三次谐波转换效率，而且使谐波光束质量显著降低；初始入射基频光束腰半径较小时，离散效应是二次谐波转换和三次谐波转换效率降低的主要因素，失谐角对三次谐波转换的影响较小；随着束腰半径的增加，离散效应的影响逐渐减小，失谐角对三次谐波转换的影响逐渐增加。     

Phase-locking resonator with annular gain media

A new type of laser resonator that is designed to extract good phase coherence and circular beams from an annular gain region is developed. We also calculated the parameters theoretically by applying the resonator to a CO₂ laser. And the transfer characteristics of the output beam from the phase-locking laser resonator through a lens are also discussed.     

基于简单透镜列阵的可调焦激光均匀辐照光学系统研究

本文对基于简单透镜列阵的大口径激光均匀辐照光学系统的调焦能力进行了研究, 结果表明, 改变透镜列阵与靶镜之间的距离即可方便地改变靶面上光斑的大小. 文中详细分析了相关参数对调焦能力的影响, 并在此基础上设计出一个实用的光学系统. 用数值方法模拟了激光束通过光学系统后的传输, 发现尺寸不同的靶面光斑具有基本一致的强度结构特征. 定量地分析了光斑内部散斑间隔、调制对比度、顶部不均匀度及能量集中度等描述光斑均匀辐照质量的指标, 并研究了它们随靶面离焦量的变化关系.     

Critical parameters influencing the material distribution produced by pulsed laser deposition

The parameters that control the thickness distribution of thin films produced by pulsed laser deposition are investigated. It is found that highly asymmetric material distribution profiles can be obtained in vacuum when high energy densities are used and the target surface is positioned at the lens focus. The asymmetries are due to asymmetries in the spatial distribution of the beam. Under Ar gas pressure, the profile becomes symmetric and the distribution narrows as a consequence of collisions between the ejected species and the gas. In vacuum, decreasing the energy density, by decreasing the laser energy output or by moving the lens to defocus the beam, leads to symmetric distribution profiles. Nevertheless, in the first case a quite broad distribution and a low deposition rate are obtained, whereas in the second case the distribution is narrow and the deposition rate increases.     

无衍射光经望远镜系统的变换

对于轴锥镜透镜产生的无衍射光，它的中心光斑半径和无衍射距离是固定的，一旦应用中要求新的光束参数，则只能再制造一个新的轴锥镜透镜。本语文提出了种用普通球面透镜望远为改变无衍射光束参数的新方法，该方法是基于无射光和环光源之间的透镜变换关系。无衍射光首先被望远系统的第一块透镜变换为一个环光源，第二块不同焦距的透镜再将该环光源变换为一个不同参数的新无衍射光。新的光束参数由两个透的焦距比值决定 。     

激光直接驱动聚变球靶初始辐照均匀性分析

采用Ｓｋｕｐｓｈｙ－Ｌｅｅ（Ｓ－Ｌ）球谐模分解方法，按一个简化的物理模型，对激光直接驱动聚变中不同束－靶条件下的靶面初始辐照不均匀度的均方根偏差进行了数值计算，由此分析了在光束完全对称排布的多光束辐照系统中，光束截面光强分布，聚焦透镜Ｆ数，离焦参数（靶心室焦距离与靶丸半径之比），光束数这几个主要因素对辐照的均匀性的影响。     

Effect of chromatic aberration on Gaussian beams: non-dispersive laser resonators

The propagation of a non-monochromatic (polychromatic) TEM₀₀ Gaussian beam in vacuum, its passage through a thin plate and its transformation by a thin lens are studied in the case of a non-dispersive laser resonator. The basic assumptions of the model are as follows: optical fields are stationary and plane-polarized, the paraxial wave equation is valid, an equivalent non-dispersive hemiconfocal resonator represents the lasing medium and its stable resonator, the laser emits in a single mode. It is also assumed that the plate and the lens have large transverse dimensions. Mathematical expressions, for beam radius, divergence, radius of curvature and beam parameter product, are obtained. A beam quality factor for polychromatic Gaussian beams is defined and its value calculated in each case of interest. It is proposed to simulate a dispersive laser resonator by a non-dispersive resonator complemented with a plate and/or a thin lens.     

Lens transformations of high power solid-state laser beams

Beam parameters of 300 W-class CW Nd:YAG lasers with double pump cavities have been investigated. The calculations have demonstrated that in the strongly pumped operating laser the amplitude of stresses in the rod can be decreased by a factor of approximately 1.5. A multibeam model of high power beam structure has been proposed. It has been shown theoretically and experimentally that 1.4–1.8 times reduction of the beam parameter product of a complex non-Gaussian beam may be achieved by placing a lens with a strength and location determined by laser parameters. An integrated parameters product has been proposed to describe the complex beams. In the range of possible pumping levels (3–10 kW) the output full divergence angle changed from 2 up to 23–28 mrad but in image space of the lens the variations of this value were no more than ±12%.     

倾斜离轴高斯-谢尔模型光束在大气湍流中通过猫眼光学镜头反射光的光强特性

本文研究了大气湍流和探测光空间相干性对倾斜离轴激光束通过猫眼光学 镜头反射光光强特性的影响. 研究表明: 由于光阑效应以及光束倾斜或离轴, 反射光光强出现振荡和非对称分布现象. 大气湍流不会改变其非对称性, 但湍流中其光强不再振荡. 当猫眼光学镜头存在微弱正离焦δ_max情况下, 轴上光强可达到最大值. 猫眼光学镜头焦距越大, 所需δ_max越大. 但是, 大气湍流和探测光相干性好坏都不会改变所需δ_max值. 在大气湍流中传输距离足够远时, 反射光强会成为离轴类高斯分布. 随着传输距离的增大, 相干性越差的探测光的反射光束扩展可以更小, 这与部分相干光自由空间传输规律完全不同. 探测光相干性越好, 其反射光强受湍流的影响越大, 但差异不大. 本文所得结果对激光主动探测的应用具有意义. 关键词： 猫眼光学镜头 大气湍流 部分相干光 光强     

Enlarging lens design with f-Θ lens for real time laser lithography inspections

An enlarging lens, composed of a charge-coupled-device (CCD) lens and an f-Θ lens, has been designed for real time laser lithography visual inspection purposes. The object of this design is to enlarge the image of the working specimens in real time, which used to be done by an independent magnifying system after the lithography process. F-Θ lens has both roles in this design, being a laser lithography lens and a specimen imaging lens. A beam splitter has been inserted between the f-Θ lens and the CCD lens, which divides the UV laser beam and the visible beam to form a coaxial system. This design also reaches the image requirements in both wavelength bands, that the value of MTF is nearly diffraction-limit in UV wavelength and greater than 0.45 at 40 c/mm in visible wavelength.     

Optimal output mirrors for laser resonators

To minimize the angular divergence of a laser output beam, the lens effect of the output mirror must be taken into account. The optimum focal length is given for symmetric and half-symmetric resonators, and the dependence of the minimum beam divergence on cavity parameters is shown.     

LD快轴准直柱透镜多参数加工公差分析理论

为了实现半导体激光器快轴准直柱透镜加工公差的快速、准确制定,在快轴光束准直理论分析的基础上,采用几何光学的方法建立了多参数加工公差理论模型。该模型以各个结构参数的极限偏差值作为公差初始值,以实际的加工精度作为边界条件,并根据具体的准直设计要求进行优化,实现各个参数公差的合理、快速分配。针对常见的TO-MOUNT型号中的一款快轴发散角为36°的半导体激光器设计了快轴准直柱透镜,利用该理论模型实现快轴准直柱透镜加工公差的快速制定,引入该公差后的ZEMAX仿真结果符合准直设计要求,且仿真的出射光束发散角与理论计算结果仅有1.1%的误差。