ICF驱动器光纤前端系统偏振控制技术

 针对ICF驱动器对光纤前端系统输出光脉冲的质量及稳定性要求，通过实验分析了光纤系统的偏振特性，实验探索了不同的偏振控制技术。并针对系统窄光谱（pm级）、短脉冲（ns级）的特点以及系统末级输出对时间特性的要求，采用空间平均的退偏振方式，能有效实现光信号的完全退偏。光纤系统增加退偏器后输出稳定性达到了1.72%，大大提高了系统输出的稳定性。     

飞秒激光在可饱和吸收体中的动力学特性

从激光动力学的自洽理论出发，推导出适用于含有可饱和吸收体的激光系统动力学方程组，研究了激光振荡的稳定性与系统参数的依赖关系，包括激励强度参数、饱和系数和能级寿命，并讨论了满足激光振荡稳定性的条件下B类激光的弛豫振荡特性。结果表明，增大激励强度与饱和系数有利于系统形成稳定的振荡输出，而且当激励强度超过一定阈值时，B类激光会产生弛豫振荡行为。     

一类非线性T-S模糊时滞系统的鲁棒观测器型H∞控制器设计

针对同时具有分布时滞和非线性项的T-S模糊时滞系统, 提出观测器型H_∞输出反馈控制器设计方法. 首先, 以非线性矩阵不等式形式给出时滞相关的满足H_∞性能指标的稳定性分析充分条件; 其次, 给出与所给稳定性条件等价的线性矩阵不等式条件. 在此基础上, 讨论带有非线性项的观测器型H_∞输出反馈控制的可解问题. 最后, 通过仿真算例说明控制器设计方法的可行性. 关键词： T-S模糊系统 分布时滞 观测器型输出反馈控制 H_∞控制')" href="#">H_∞控制     

再生锁模激光系统的定态输出及其稳定性

将准孤子解代入再生锁模激光系统的主方程，推导出脉冲参量的三个自治微分方程. 求解了无啁啾和有啁啾两种情况下系统的定态解，并分析了其稳定性. 研究表明，系统的定态输出随系统的调制深度或调制频率、群速色散或自相位调制等参量值的变化而变化. 因此，通过调制系统的参量可以控制激光系统的定态输出. 关键词： 再生锁模激光系统 线性稳定性分析 罗斯-霍维茨判据 定态输出及其稳定性     

应用级联倍频方法提高倍频系统输出稳定性研究

提出应用级联倍频方法提高倍频系统输出稳定性,并就该方法的有效性进行了理论分析和模拟计算.分析和计算结果不但证明级联倍频方法能实现倍频系统稳定输出,而且还表明可以通过仔细调节第一块倍频晶体中波矢方向 k 与光轴间夹角、两块倍频晶体间的间隔,能调节改变实现倍频系统最稳输出时所需第二块晶体的理论计算长度,使之与第二块倍频晶体的实际加工长度一致,最终实现系统稳定倍频输出.级联倍频方法在实现高输出稳定性的同时能实现高的倍频转换效率,对应用于光参量啁啾脉冲放大系统的高稳定抽运源系统的设计建造具有重要参考意义. 关键词： 级联倍频 稳定倍频输出 光参量啁啾脉冲放大     

谱线可调折迭-复合腔的稳定性研究

一般的红外调谐激光器,不仅功率低,而且谱线稳定性和功率稳定性都很差。外界条件的变化很容易造成谱线和强度的起伏。我们曾用折迭-复合腔获得高功率可调谱线CO_2激光输出。它的特点是用普通玻璃基板的红外光栅可获得80W高功率输出。本文着重讨论用这种腔怎样获得长时间的谱线稳定性和功率稳定性(功率起伏小于5％/hr),并试图解释谱线稳定度的自动控制现象。     

混沌Lur’e系统的线性输出反馈同步

针对一类特殊的混沌Lur’e系统,以系统最后一状态变量作为驱动信号进行误差的线性输出反馈,提出一个同步的全局控制规律,并证明了同步的渐近稳定性.最后以蔡氏振子为例进行仿真,验证该同步方法的有效性. 关键词： 混沌同步 输出反馈 Lur’e系统 蔡氏振子     

高质量高效率高稳定性参量放大光产生的研究

针对光参量放大实验中存在的参量转换效率低、输出光脉冲形状畸变和输出稳定性差等问题进行了详细研究，对注入信号光强、抽运光耗尽、增益饱和、和频过程等因素对参量过程的影响进行了详细分析讨论，并进行了光学参量放大的实验研究.理论和实验研究结果表明通过优化选择合适的注入信号光强、抽运光强和晶体长度等参数，使参量放大运行在深度增益饱和状态的稳定区，完全可以获得高质量高效率高稳定性的参量放大输出光. 关键词： 光参量放大 抽运光耗尽 增益饱和 稳定性     

多输入多输出不确定非线性系统的输出反馈自适应机动控制

输出机动控制问题通常由几何任务和动态任务两部分组成.对具有参数不确定性的多输入多输出非线性系统,研究了其基于输出反馈的自适应机动控制问题.通过引入滤波器和观测器来实现对不可量测系统状态的虚拟估计.利用向量形式的Backstepping反推方法,构造出了输出反馈自适应控制器,并给出了三种路径变量自适应律设计方案.所提出的控制方案保证了闭环系统的全局渐近稳定性,使得系统同时完成几何任务和动态任务.最后的仿真结果验证了本方法的有效性. 关键词： 输出反馈 非线性系统 输出机动 反推     

用CCD摄像机检测激光器输出光束的指向稳定性

报导用CCD摄像机检测激光器输出光束的指向稳定性的实验结果。系统由计算机控制，可同时显示远场光斑形状及强度分布。测量He-Ne激光器、半导体激光器及氩离子激光器指向稳定性及激光束输出强度的稳定性。     

Weak versus strong harmonic-expansion analyses of self-pulsing lasers: I—the Laser Lorenz model

We apply a simple harmonic expansion method to the single-mode laser equations to analyze their dynamic properties. First, we extend the well-known small signal analysis to predict the transient pulsations of the relaxation oscillations. Such transients are characteristic of the laser signal relaxing towards its long-term solution, at any level of excitation, both beyond and below the instability threshold. Secondly, we extend the method to a strong harmonic expansion to analyze the properties of the long-term solutions. These properties are derived for typical examples, extending well beyond the boundary region of the instability domain, for which the laser field amplitude undergoes regular pulsations around zero-mean values.     

Coexistence of single-mode and multi-longitudinal mode emission in the ring laser model

A homogeneously broadened unidirectional ring laser can emit in several longitudinal modes for large enough pump and cavity length because of Rabi splitting induced gain. This is the so called Risken-Nummedal-Graham-Haken (RNGH) instability. We investigate numerically the properties of the multi-mode solution. We show that this solution can coexist with the single-mode one, and its stability domain can extend to pump values smaller than the critical pump of the RNGH instability. Moreover, we show that the multi-mode solution for large pump values is affected by two different instabilities: a pitchfork bifurcation, which preserves phase-locking, and a Hopf bifurcation, which destroys it.     

Femtosecond-laser-based synthesis of ultrastable microwave signals from optical frequency references

We use femtosecond laser frequency combs to convert optical frequency references to the microwave domain, where we demonstrate the synthesis of 10-GHz signals having a fractional frequency instability of < or =3.5 x 10(-15) at a 1-s averaging time, limited by the optical reference. The residual instability and phase noise of the femtosecond-laser-based frequency synthesizers are 6.5 x 10(-16) at 1 s and -98 dBc/Hz at a 1-Hz offset from the 10-GHz carrier, respectively. The timing jitter of the microwave signals is 3.3 fs.     

Update on ignition studies at CEA

This article sums up the theoretical and experimental studies about ignition. Three experiments are salient this year on the Omega laser in collaboration with DOE laboratories (1) 3 cones of beams allow to mimic the LMJ configuration and to get symmetry measurements. (2) We measured perturbations due to hydro-instability in CHGe planar samples with face-on and side-on radiographs. (3) We improved our nuclear diagnostics, particularly the neutron image system tested on direct drive implosions. As far as LMJ target design is concerned, we defined a preliminary domain corresponding to the possible operation at 2ω. At 3ω we studied the low mode instability effects on the DT deformation (due to the laser or to the target) and on the yield. The stability is clearly improved with graded doped CH for our nominal capsule L1215.     

混沌光通信与混沌激光测距的研究进展

激光器的不稳定性是一个普遍现象,而混沌是激光器不稳定性的一个重要特例。近年来,基于混沌激光的一些应用技术相继被提出及完善。结合国内外研究现状,简要介绍了混沌激光在通信及测量领域的应用,包括混沌保密通信、混沌激光雷达和混沌光时域反射仪等技术,并指出了混沌光通信与混沌激光测距的发展趋势。     

Transferring the stability of iodine-stabilized diode laser at 634 nm to radio frequency by an optical frequency comb

An optical flequency comb phase-locked on an iodine frequency stabilized diode laser at 634 nm is constructed to transfer the accuracy and stability from the optical domain to the radio frequency domain. An external-cavity diode laser is frequency-stabilized on the Doppler-free absorption signals of the hyperfine transition R（80）8-4 using the third-harmonic detection technique. The instability of the ultra-stable optical oscillator is determined to be 7 ×10^-12 by a cesium atomic clock via the optical frequency comb＇s mass frequencv dividing technique.     

Instabilities in optically pumped infrared lasers

The unstable emission of an optically pumped FIR gas laser is theoretically analysed through numerical resolution of the associated Maxwell-Bloch equations. The instability domain in the main control parameters space is determined and an example of chaotic behaviour is examined.     

Filamentation of laser radiation in DC biased GaAs

In this paper, we have examined the filamentation instability of laser radiation in a GaAs sample in the negative differential resistivity region. A dc electric field is applied to assist the laser beam transferring electrons in the conduction band from the lower valley to upper satellite valleys, i.e. in increasing the effective mass of electrons. The instability causes the space charge perturbations in the microwave range of frequencies. The nonlinearity arises through the energy dependence of the effective mass and the ponderomotive force on the electrons. The instability has finite frequency and possesses large growth rate which is greatly influenced by the dc electric field.     

Emergence of unstable modes in an expanding domain for energy-conserving wave equations

Motivated by recent work on instabilities in expanding domains in reaction-diffusion settings, we propose an analog of such mechanisms in energy-conserving wave equations. In particular, we consider a nonlinear Schrödinger equation in a finite domain and show how the expansion or contraction of the domain, under appropriate conditions, can destabilize its originally stable solutions through the modulational instability mechanism. Using both real and Fourier space diagnostics, we monitor and control the crossing of the instability threshold and, hence, the activation of the instability. We also consider how the manifestation of this mechanism is modified in a spatially inhomogeneous setting, namely in the presence of an external parabolic potential, which is relevant to trapped Bose-Einstein condensates.     

Effect of self-generated magnetic field on the two-plasmon decay instability in a laser-produced plasma

Summary In this paper we have made a theoretical investigation on the two-plasmon decay instability of laser radiation in the presence of the selfgenerated magnetic field at the quarter-critical density region in a laserproduced plasma. The Vlasov equation in terms of guiding centre coordinates has been employed to obtain the nonlinear response of electrons in the plasma. The threshold power density of the incident laser radiation for the two-plasmon decay instability is always exceeded in currently employed power densities in laser-target experiments and above the threshold the growth rate of the instability is quite large. It is also noticed that the selfgenerated magnetic field enhances the threshold to a large extent, thus drastically reducing the growth rate of the instability. To speed up publication, the author of this paper has agreed to not receive the proofs for correction