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1.
唐前进  陈大明  于永爱  胡企铨 《中国物理》2006,15(11):2609-2617
Based on the Collins integral formula, the analytic expressions of propagation of the coherent and the incoherent off-axis Hermite-cosh-Gaussian (HChG) beam combinations with rectangular symmetry passing through a paraxial first-order optical system are derived, and corresponding numerical examples are given and analysed. The resulting beam quality is discussed in terms of power in the bucket (PIB). The study suggests that the resulting beam cannot keep the initial intensity shape during the propagation and the beam quality for coherent mode is not always better than that for incoherent mode. Reviewing the numerical simulations of Gaussian, Hermite-Gaussian (HG) and cosh- Gaussian (ChG) beam combinations indicates that the Hermite polynomial exerts a chief influence on the irradiance profile of composite beam and far field power concentration.  相似文献   

2.
In the letter the polarization properties of quasi-homogenous (QH) beam propagating in Kolmogorov and non-Kolmogorov turbulence are studied. The results show that the polarization properties of QH beam undergoes three stages during the propagation in turbulence: in the "near field", the degree of polarization (Dop) and the state of polarization (Sop) fluctuate with source parameters and transverse position; after that the beam come to the "middle field" where its properties are affected by source parameters and turbulence perturbation; in the final "far field", the values come to constants which dependent only on source parameters.  相似文献   

3.
Smoothing by spectral dispersion (SSD) leads to considerable improvement on laser-irradiation uniformity in far field for fusion lasers. Phase modulation in time and spectral angular dispersion (SAD) across the beam introduced by SSD will affect the stimulated rotational Raman scattering (SRRS) gain in the near field. This paper focuses on the influence of SAD on SRRS gain under different laser conditions. Results show that the SAD will aggravate the generation of SRRS when the laser initial additional phase is constant. On the contrary, the SAD can reduce the SRRS gain if appropriate SSD parameters are adopted when the laser initial additional phase is variable. SSD has a certain application prospect in SRRS suppression.  相似文献   

4.
周国泉  倪涌舟  储修祥 《中国物理》2007,16(11):3377-3381
Based on the vector angular spectrum representation of optical beam and the method of stationary phase, the analytical TE and TM terms of vector Gaussian beam have been presented in the far field. By using the local polarization matrix, the polarization properties of the TE and TM terms in the far field are investigated, and it is found that the degree of their polarization is only determined by the spatial location. When the source is completely polarized, the TE and TM terms are both completely polarized in the far field. When the source is completely unpolarized, the TE and TM terms in the far field are partially polarized. The whole beam is also partially polarized except on the propagating axis. Moreover, the degrees of polarization of TE and TM terms are both larger than that of the whole beam.[第一段]  相似文献   

5.
陆世专  游开明  陈列尊  王友文 《中国物理 B》2011,20(3):34202-034202
The approximate analytical expressions of the apertured broadband beams in the far field with Gaussian and Laguerre-Gaussian spatial modes are presented.For the radially polarized Laguerre-Gaussian beam,the result reveals that the electromagnetic field in the far field is transverse magnetic.The influences of bandwidth(Γ) and truncation parameter(C 0) on the transverse intensity distribution of the Gaussian beam and on the energy flux distribution of radially polarized Laguerre-Gaussian beam are analysed.  相似文献   

6.
周国泉  陈亮  储修祥 《中国物理》2007,16(9):2709-2715
Based on the vectorial structure of electromagnetic beam and the method of stationary phase, the analytical structure of Hermite Gaussian beam in far field is presented. The structural energy flux distributions are also investigated in the far field. The structural pictures of some Hermite Gaussian beams are depicted in the far field. As the structure of Hermite Gaussian beam is dominated by the transverse mode numbers and the initial transverse Gaussian half width, it is more complex than that of Gaussian beam. The ratios of the structural energy fluxes to the whole energy flux are independent of the transverse mode numbers and the initial transverse Gaussian half width. The present research reveals the internal vectorial structure of Hermite Gaussian beam from other viewpoint.  相似文献   

7.
In this letter, numerical simulation and experimental study of a radial-slab solid-state laser are presented. The laser includes four crossing-slabs pumped by four Xe flashlamps. The numerical simulation of coherent intensity in the near field and the far field indicates that the laser with the structure can improve the quality of output beam compared with incoherent beam combination. The radial-slab solid-state laser is fabricated, and initial experiments are carried out at a pulse repetition of 1 Hz. Nine beams in the near field and one combined beam in the far field are obtained in our initial experiment. The experimental results are consistent with the numerical analysis in the coherent condition. The results show that coherent beam combination is obtained by this laser.  相似文献   

8.
Based on the orthogonalities of the vector wave functions, the expressions of scattering fields are developed as the particle in the zero order field and in the first order fields of x, y, and z, respectively. A general relation between the expansion coefficients of scattering field and incident field is presented. Taking the elliptical beam for example, the scattering property of a particle in beam is investigated. After analyzing the effects of the beam waist, irradiating distance, etc. on scattering property, the validity of the proposed algorithm is demonstrated. Results show that the beam waist may improve the particle identification property and the particle has a strong scattering both in the forward direction and in the backward direction. The method proposed is simple and is a new way of researching the scattering from particles in electromagnetic beams.  相似文献   

9.
胡先权  许杰  罗光  马燕 《中国物理》2007,16(12):3631-3636
The model of the Coulomb dressed potential is applied to solving the problem of electron scattering for simplifying the calculation in the electrostatic field and the excimer laser field. The introduction and the application of the model are based on the electric dipole approximation, so the contribution of the electric multipole is neglected. In this paper, rigorous analysis and deduction are carried out for the introduction of the dressed Coulomb potential into the laser field. It is found that the introduction of the dressed potential in the fractional form is feasible only when the laser field (not including far ultraviolet field and x-ray) is a weak field, i.e. the quiver radius of the free electron is smaller than the atomic scale. In addition, the necessary analysis is also conducted of the limitation of the application of the Coulomb dressed potential.  相似文献   

10.
A one-dimensional (1D) top-hat, diode-end-pumped, electro-optically Q-switched Nd:YVO4 slab laser is demonstrated. Under the pump power of 175.5 W, 26.3-W output power is obtained with the repetition rate of 5 kHz and the pulse width of 4.3 ns. The output beam has a good top-hat beam profile in both the near field and the far field.  相似文献   

11.
 用光强沿x轴方向呈线性变化的方形环状光束模拟高功率激光,利用自编四维仿真程序对高功率激光在光束控制系统中的传输作了详细的数值计算研究。结果表明:热效应使远场光束的峰值光强和可聚焦能力下降。入射光强的非均匀分布进一步降低峰值光强和可聚焦能力,导致远场光束重心和峰值光强位置移动,并产生像散。光束的非均匀程度越高,远场光束质量越差。横向风和轴向风对热效应均有抑制作用。然而,轴向风不会引起远场光束重心偏移和像散,但是轴向风比横向风建立稳态所用时间更长。  相似文献   

12.
对激光惯性约束聚变(ICF)驱动器终端光学系统中连续相位板(CPP)的位置优化进行了研究.根据高强度激光非线性及微扰传输理论计算了CPP前置时激光通过频率转换系统以后的近远场光束特性和系统的三倍频转换效率.研究发现,前置于基频光路的CPP对三倍频转换效率和出射光束特性均有影响,但只要远场圆形焦斑直径小于05 mm,三倍频转换效率的下降与出射光束通量对比度的上升均在容许范围之内,同时远场焦斑形态和能量集中度也符合设计要求.对于实现远场小焦斑匀滑的CPP前置于ICF的基频光路中进行光束匀滑和整形,不会对IC 关键词: 连续相位板 束匀滑元件 惯性约束聚变 光束通量对比度  相似文献   

13.
光学相控阵光偏转器的驱动研究   总被引:5,自引:4,他引:1  
提出了一个用于16通道波导光学相控阵光偏转器的驱动系统, 其中电压调节控制单元用一个现场可编程门阵列(FPGA)芯片实现.这个系统可使该OPABD的光束扫描速率达到580 kHz以上, 远远高于基于微控制器的驱动系统所能达到的水平.  相似文献   

14.
径向剪切干涉法综合诊断光束质量研究   总被引:4,自引:1,他引:3       下载免费PDF全文
 为了解决高功率激光装置光束质量诊断系统的自验证问题,研究了基于空间相位调制的径向剪切干涉法综合诊断光束质量的实验应用。该方法理论上只需一台干涉仪且从单幅干涉图中获取光束的近场、相位和远场分布信息。实验结果表明,目前可以得到高分辨率的相位分布,由测量近场和相位恢复出的远场同CCD直接测量得到的远场形态相同,环围能量比曲线相当吻合,不足之处在于只能提取近场较低空间频率成分,还达不到CCD直接测量的空间分辨水平。  相似文献   

15.
Based on the vector angular spectrum method and the method of stationary phase, an analytical expression for the vectorial structure of the far field of an elegant Hermite–Gaussian beam is derived. The analytical formulae of the energy flux distributions of the TE term, the TM term, and the whole beam are presented in the far field. Analytical expressions for the ratios of the powers of the TE and TM terms to those of the elegant Hermite–Gaussian beam are obtained without any approximation. The physical pictures of the far field of an elegant Hermite–Gaussian beam are demonstrated and compared with those of the far field of the corresponding standard Hermite–Gaussian beam. This research reveals the internal vectorial structure of the far field of an elegant Hermite–Gaussian beam from an alternative viewpoint.  相似文献   

16.
激光远场焦斑测试技术的实验研究   总被引:6,自引:3,他引:3       下载免费PDF全文
 实验研究了激光远场焦斑能量分布测试的三种方法(长焦距透镜法、列阵相机法、Rattle Pair法),对三种测试方法得到的实验数据进行了比对,系统地分析了每种方法的优缺点。结果表明,采用长焦距透镜与一对微楔角劈板组合测试激光远场焦斑的方法更具优势,可减少测试系统引入的像差,并使图像处理过程得到简化。  相似文献   

17.
四程放大自动准直系统数学模型研究   总被引:1,自引:0,他引:1       下载免费PDF全文
针对高功率激光装置四程放大系统的特点,利用矩阵光学原理,建立了四程放大准直系统的数学模型;基于此模型,设计了四程放大系统的准直调整方案;得出了近、远场偏移量与调整量关系的解析解. 关键词: 激光技术 光束准直 四程放大  相似文献   

18.
We propose and demonstrate the generation of dark hollow beam with plane wavefront in the near field based on a hybrid control way by using dual phase only liquid crystal spatial light modulators (LC-SLMs). One phase only LC-SLM redistributes the intensity to the target distribution based on refractive beam shaping system and the other phase only LC-SLM adaptively compensates the wavefront of the output beam by using stochastic parallel gradient descent (SPGD) algorithm. Compared with conventional refractive beam shaping system, the hybrid control way can not only improve the far-field energy concentration of the output beam, but also can correct the phase distortion of the system. Influences of phase distortion on laser beam shaping are analyzed in detail. The theoretical and experimental results show that the near-diffraction-limited dark hollow beam can be successfully generated by using this hybrid control way. The power in the main lobe of the airy disk pattern area in the far field is 2.3 times larger than that without being adaptively compensated.  相似文献   

19.
Far field structural characteristics of cosh-Gaussian beam   总被引:1,自引:0,他引:1  
By means of the theorem of the vectorial structure of electromagnetic beams and the method of stationary phase, the analytical vectorial structure of cosh-Gaussian (ChG) beam in the far field is presented. The light intensity distributions of a ChG beam and its vectorial structure are investigated in the far field. In addition, the influence of the parameters associated with the cosh term on the light intensity distributions of the whole beam and its structure are also analyzed. The analytical formulae obtained here are applicable not only to the non-paraxial case, but also to the paraxial case. The physical picture of ChG beam in the far field is well depicted from the vectorial structure.  相似文献   

20.
Free and forced motions of submerged one-dimensional waveguides have been investigated. Both the submerged beam and the submerged string can support a wave system which includes a pure surface wave in the fluid adjoining the waveguide, provided that certain conditions on the frequency (for the beam) or the physical parameters of the system (for the string) are satisfied. Dispersion curves are presented for steel beams and steel strings in water. Steady-state solutions have been derived for excitation by a concentrated time-harmonic load. The displacement responses at the point of application of the load and in the far field have been examined. Polar plots display and radiated far field in the fluid. At low frequencies the polar plots are circular in planes containing the waveguide, but the radiation pattern develops lobes as the frequency increases. Reflection, transmission and scattering into the fluid of an incident wave system by an elastic support of stiffness κ and mass m have also been examined, and the possibility of resonance phenomena has been investigated.  相似文献   

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