Theoretical Description of the Third Order Parametric Wave Mixing in a Gas-Filled Capillary of Femto-Second Laser Pulse

The theoretical signal-pressure curves are calculated from approximate analytical solutions of the coupled equations describing the third order parametric wave mixing in a gas-filled capillary of femto-second laser pulses, The comparison with the corresponding experimental curves suggests that the following three factors exert important influences on the degree of fitting between the theoretical and experimental results: the walk-off, the phase modulation, and the third order harmonic of idler pulse.     

Signal-Pressure Curves of Cascaded Four-Wave Mixing in Gas-Filled Capillary by fs Pulses

The theoretical framework for the cascaded four waves mixing (CFWM) in gas-filled capillary by fs pulses is constructed. Based on the theoretical framework, the signal-pressure curves (SPC) of the CFWM in gas-filled capillary by fs pulses are calculated. With a comparison between the theoretical and experimental SPC we have discussed the influence of the walk-off and phase modulation on the SPC. At the same time, we have discussed the possible origin of the first three peaks of the SPC.     

Third-Harmonic Generated in EH32 Mode of a Gas-Filled WavegUide by fs Laser Pulses

In this paper it is reported for the first time that the third harmonic generated in EH32 mode of a gas-filled waveguide by fs pulses has higher generation efficiency. The new finding contrasts with the experiment in It. G. Durfee Ⅲ, S. Backus, M.M. Murnane, and H.C. Kapteyn, Opt. Left. 22 （1997） 1565]. Some possible factors, which produce the contradiction, are discussed briefly.     

在单晶硅中用相干光耦合方法压缩短脉冲和超短脉冲

提出一种新型的相干光耦合压缩短脉冲和超短脉冲的方法。以硅为非线性材料，经计算表明：在材料的破坏阈值之内，出射信号光脉冲的脉宽可被压缩到入射光脉宽的７０％。计算了泵浦能量密度，泵浦光与信号光夹角等与脉宽压缩量的关系。     

Lower Order and Higher Order Entanglement in Four‐Wave Mixing Process

Possibilities of generation of lower order and higher order intermodal entanglement in four‐wave mixing (FWM) process are rigorously investigated using Sen‐Mandal perturbative technique. The investigation has revealed that for a set of experimentally realizable parameters, one can observe lower order and higher order intermodal entanglement between pump and signal modes and signal and idler modes in a FWM process. In addition, trimodal entanglement involving pump, signal and idler modes is also reported.     

充气毛细管中飞秒激光四波混频的理论描述

建立了一个描写充气毛细管中飞秒激光四波混频过程的理论框架.在 这个理论框架的基础上，对最近得到的充气毛细管中飞秒激光四波混频过程的信号强度气 压实验曲线给出了初步的理论说明．发现考虑走离效应和相调制效应对充气毛细管中飞秒激 光四波混频过程有重要的作用．同时还发现在一定的条件下，考虑直接的三次谐波过程对实 验曲线的影响是必要的. 关键词： 四波混频 飞秒激光 充气毛细管     

Approximate Theoretical Study on the Characteristic of a Femtosecond KLM Laser

The conclusion that the pulse-width is proportional to the square root of the third order dispersion coefficient is obtained by using the modified higher-order nonlinear Schr?dinger equation with concurrent actions of third order dispersion and self-steepen effect when a femtosecond pulse propagates steadily in a laser. This result is in agreement with the experimental result. Besides, the action of second order dispersion term is also discussed in the realization of mode locking process of a laser.     

Approximate Theoretical Study on the Characteristic of a Femtosecond KLM Laser

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飞秒强激光在充气毛细管中产生三次谐波的效率

利用描写飞秒强激光在充气毛细管中产生三次谐波的一个理论模型讨论了三次谐波产生的信号-压强曲线.结果发现：在毛细管参量和激光参量确定的条件下，三次谐波效率受管内气压，三次谐波模式，走离效应（walk-off）和相调制效应的影响.同时，发现，得到的三次谐波效率接近实验值. 关键词： 效率 三次谐波 飞秒激光 充气毛细管     

Properties of Optical Phase-Locked Loop Based on Four Wave Mixing in Semiconductor Laser Amplifiers

In this paper, the properties of the optical phase-locked loop(PLL) based on the four-wave mixing in the semiconductor laser amplifiers (SLAs) are discussed. The components that achieve the function of detecting the bit phase of the input optical signal are concerned and discussed in detail together as a function module named as the optical bit phase detector referred to the general electronic PLL. Therefore, most of the properties of the optical PLL can be analyzed by applying the general phase-locked theory. Here the stability of the optical PLL is discussed. It's shown that the variance of input signal power in the practical application will cause optical PLL system unstable because of its long loop delay. The influence on the output phase jitter of the optical PLL is also investigated.     

空气中飞秒脉冲激光器互相关信号的理论研究

利用色散脉冲传播理论和空气折射率Ciddor公式,推导了空气中飞秒脉冲激光器的互相关函数;根据互相关函数结果表达式取决于激光器光源的光谱分布,建立了在空气中不同光程路径差及环境参量变化下,不同光谱分布的飞秒脉冲激光器的脉冲之间互相关模式的数值模型.结果表明:随着传播距离的增大,互相关模型具有稳定啁啾及线性加宽;环境参量的变化只引起互相关图案的移动,并不产生任何额外线性加宽或啁啾.     

Physical Interpretation of the Motion of a Laser Pulse within the Framework of the Four-Oscillator Model

A physical multidimensional local model of the propagation process of a laser pulse in air having no analogy to famous models in laser physics is constructed. It is based on the representations of classical wave mechanics characteristic of the theory of scalar wave fields.     

基片衍射对会聚激光驻波场中原子波包几率密度演化的影响

针对激光会聚铬原子沉积实验,运用标量衍射理论,通过数值模拟研究了基片衍射对会聚激光驻波场中原子波包几率密度演化的影响。结果显示基片衍射的影响会随激光中轴线与基片沉积表面距离b0的变化而变化。相对于非衍射情况,衍射效应会提高激光驻波场中会聚平面内原子波包几率密度分布的中心值,同时减小其半峰全宽。当参量b0=－0.2w0(w0为高斯光束的束腰半径)时,原子波包几率密度的会聚平面和基片沉积表面完全重合。此处,衍射时原子波包几率密度分布的中心值为1.26,其半峰全宽为5.62 nm,两者分别为非衍射时的1.1倍和0.94倍。     

Characteristics of the Spectra of a Plasma near the Surface of Solid and Liquid Targets Exprosed to a Laser Pulse of Complex Form

The results of investigation of the dynamics of the emission spectra of a plasma generated at the surface of liquid and solid targets by a laser pulse of a complex time form are presented. It is shown that the shock wave arising as a result of breakdown on the surface of the solid and developing to heights of the order of 4 mm is a laser-supported detonation shock wave. In the case of solid targets, we recorded additional laser plasma light pulses coming after the main pulse. Two additional light pulses have been recorded for the emission line AlI 396.1 nm. In the case of the liquid, we have not detected additional pulses for the investigated emission lines of the elements at the laser radiation power densities used.     

2+1维U(1)改进格点规范理论中0++胶球波函数的三阶结果

用改进的格点规范场哈密顿量和截断本征方程法计算2+1维U(1)规范场的0++胶球波函数，三阶结果比二阶结果的标度行为有了较大的改善.     

量子模型分析激光驻波原子透镜的像差

采用量子模型对近共振激光驻波原子透镜会聚Cr原子束、形成纳米量级光栅结构的物理过程进行数值模拟。为提高原子透镜的成像质量,对各种像差,如衍射像差、球差、色差、及原子束发散角、原子磁支能级、原子同位素等因素引起的像差进行了理论分析。模拟结果表明,相比粒子光学模型,量子模型能更加精确地描述原子会聚结果,且能解释原子在驻波光场中的衍射现象。在各种像差中,原子束发散角是最主要的因素,其影响大于衍射像差、球差、色差。原子的磁支能级、同位素等因素对像差影响很小,可以忽略不计。激光冷却准直原子束的方法可以减小束发散角引起的像差,压缩原子速度Vz分布范围的方法可以减小色差。     

Anomalies in the Absorption and Reflection of a High-Power Ultrashort Laser Pulse by a Plasma with a Solid-State Density

The patterns of absorption and reflection of an ultrashort laser pulse by a plasma with a solid-state density, which are realized in the mode of the normal skin effect, are studied. It is shown that a decrease in low-power pulse duration shorter than the period corresponding to the fundamental frequency of radiation leads to an increase in the absorption coefficient. If the pulse power is so high as to provide electron heating during a time shorter than the reciprocal fundamental frequency, nonlinear suppression of absorption takes place and the spectrum of the reflected radiation contains odd harmonics of the fundamental frequency.