New FIR Laser Lines from CHD2OH Methanol

We have investigated CHD₂OH methanol as source of far-infrared (FIR) laser radiation using the optical pumping technique. Our new waveguide pulsed CO₂ laser, with peak powers as high as some kW, has allowed us to observe 12 new lines. Each of them is characterized in wavelength, relative polarization, intensity, optimum operating pressure and pump offset from the center of the exciting CO₂ line.     

More precise determination of thermal lens focal length for end-pumped solid-state lasers

A method of more precise determination of the focal length of equivalent thermal lens (TL) is presented in this paper. The method is based on the diffraction theory of aberrations. By numerically calculating the optical path difference (OPD) distribution and the Strehl ratio, the focal lengths for “top-hat” pumping and Gaussian pumping are obtained and the equations for the focal lengths are presented by curve fitting. Also the equations for average pump radii are presented. The experiment on a fiber-coupled LD pumped Nd:YAG laser is carried out. The experimental results verify the validity of the method.     

Spectral distributions of harmonic generation from electron oscillation driven by intense femtosecond laser pulses

The characteristics of harmonic radiation due to electron oscillation driven by an intense femtosecond laser pulse are analyzed considering a single electron model. An interesting modulated structure of the spectrum is observed and analyzed for different polarization. Higher order harmonic radiations are possible for a sufficiently intense driving laser pulse. We have shown that for a realistic pulsed photon beam, the spectrum of the radiation is red shifted as well as broadened because of changes in the longitudinal velocity of the electrons during the laser pulse. These effects are more pronounced at higher laser intensities giving rise to higher order harmonics that eventually leads to a continuous spectrum. Numerical simulations have further shown that by increasing the laser pulse width broadening of the high harmonic radiations can be limited.     

Particle sizing by time-resolved Mie calculations—A numerical study

If a small transparent particle is illuminated with a short laser pulse, the signals of the individual scattering light orders appear temporally successively. Since to each scattered light order belongs a specific optical path through the particle, the particle size can be determined from the time difference between the detected scattered light signals. For the case of a detector position within the backscatter region, which especially is important in measuring practice, the time difference between the specular reflection signal and the signal after a single internal reflection (refraction of second order) must to be evaluated. In the numerical simulation we generate the concerned scattered light signals by using time-resolved Mie calculations and in this paper we present the geometrical models, which permit a correct interpretation of the temporal behavior of these pulse-induced scattered light signals.     

激光衍射测量中应用插值细分的可行性分析

激光衍射测微的精度关键在于衍射图样暗纹间距的精确测量，暗纹间距的测量目前主要采用高位数、小中心距的固体图象传感器线阵，为此，提出了一种硬件插值细分的方法。介绍了激光衍射的测量原理，分析了图像传感器的功能，根据采样和恢复定理，对输出的视频信号进行间距插值细分的可行性进行了论证，给出了插值细分的电路框图。分析表明其测量精度不受器件中心距大小的限制，为低位数、大中心距的固体图象传感器线阵的应用提供了方便。     

非简并Λ型三能级原子的速度选择相干布居俘获

研究了非简并Λ型三能级原子速度选择相干布居俘获与原子能级结构的非对称性以及原子-激光失谐之间的关系.指出相对于简并、共振情况，原子动量分布的概率峰峰值降低、最可几动量发生变化，而且原子的俘获时间也变得很长.     

二维随机介质中准态模的频谱时间演化特性

采用时域有限差分法数值求解Maxwell方程组，分析了平面随机介质中光波模式的频谱时间演化特性.随机介质的特征可以用散射颗粒的随机构形、介质参数（如颗粒的尺寸和填充率等）以及介质形态等因素来描述.这些因素决定了随机介质在准稳态下模式的频率特性与数量，但具有不同因素的随机介质中模式的产生、选择与演化，具有大致相同的特征与速度.平面随机介质的这些冷腔特性，与传统光腔中模式的产生、选择和演化的特征非常相似. 关键词： 激光物理 随机激光器 无序介质中的光学特性     

傅立叶变换激光腔内吸收光谱方法研究吸收谱线的强度与线形

在原有傅立叶变换激光腔内吸收光谱实验装置的基础上,利用信号差分方法减少了光强波动对实验干涉谱图的影响,改善了信噪比.通过对大气中氧气在760nm处的吸收谱线的绝对强度测量,验证了该方法的定量测量能力.在不同压力条件下对磷烷v=6伸缩局域模泛频吸收谱带进行了测量,获得了其谱线的自压力加宽和自压力线移参数.     

NO分子A2Σ→X2Π双光子激光感生荧光光谱

以Nd∶YAG激光器抽运光学参变振荡器 /光学参变放大器做为激发源 ,得到了NO分子在 2 2 0～ 35 0nm波长范围内的双光子激光诱导荧光光谱 ,并将其归属于A2 Σ(ν′ =0 )→X2 Π(ν″ =1～ 8)跃迁 ,用最小二乘法拟合获得NO分子X2 Π态振动常量″ωe =(190 4 .7± 7.3)cm-1,″ωe ″xe =(14 .2± 1.2 )cm-1,″ωe″ye=- (0 .0 2 18± 0 .0 0 91)cm-1,及平衡位置的力常量k =(1.5 99± 0 .0 12 )× 10 3 N·m-1。计算了所得跃迁谱带的弗兰克康登因子及相对荧光强度 ,结果与实验观测值相符。这可为用激光诱导荧光光谱技术探测大气污染物NO分子提供理论及实验参考     

A new design for a high-power, tail-free high repetition frequency single-mode CO2 laser

A new discharge design for pulsed CO2 lasers has been made with a series of short longitudinal synchronous discharges working at high pressure with large section. In this way, single-mode high-power (up to 40 kW at 100 ns) tail-free pulses have been obtained at intermediate repetition frequency (25 Hz) in a He-free mixture dominated by CO₂ (75–90% content). This laser is ideal for producing frequency mixing in non-linear crystals.