喇曼自由电子激光器辐射谱的测量

本文报道了利用微波栅摄谱仪测量在超辐射工作条件下的喇曼自由电子激光器辐射谱的初步结果。观察到了毫米波自由电子激光器的调谐特性。实验结果表明,辐射谱的中心频率随波荡场强度的增加而减小,这与考虑波导模影响的集体制式自由电子激光的有关理论预言相符。     

连续可调的喇曼自由电子激光器

麻省理工学院已经证明了自由电子激光器在7~18 GHz频率之间的连续调谐作用。在该学院物理研究生J.法简斯及其同事合作进行的实验中，对单波导模和集合喇曼方式工作的自由电子激光器的调谐特性进行了演示。     

喇曼自由电子激光器的实验研究

我们研制了一台基于受激喇曼散射的自由电子激光器。精心设计的无箔二极管发射出柱状或空心柱状电子束。电子束打靶实验表明它是高度准直的;利用Lamor运动实验测试出电子束的归一化发射度为23π·mrad-cm,完全满足受激喇曼散射模式判据。该电子束在抽空为5×10~(-5)Torr、内径φ20mm的漂移管中传输,受到右旋圆偏极双绕电磁波荡器或轴对称铁环波荡器(周期分别为2.2cm及2.25cm)的泵浦,均获得超辐射模式的自由电子激光辐射。测     

喇曼自由电子激光器二极管的实验研究

文章给出了用于一台喇曼自由电子激光器磁场浸没型无箔二极管工作特性的实验研究。比较了不同结构、不同电极参量、不同电极材料和不同磁场下的典型结果。分析了不同的束输出条件下所遵循的规律。     

喇曼自由电子激光器电子束速度分散度的测量

我们建造的一台喇曼自由电子激光器巳投入运转。其电子束能量为0.5MeV,束流为0.1～1kA。作为该激光器参量研究的一部分,我们测试了电子束的轴向速度分散度。 为使电子束的集体效应占主导地位(即激光器工作在受激喇曼散射模式),电子束必须足够“冷”,其轴向速度分散度Δν_x应满足如下判据:     

三毫米波喇曼自由电子激光器实验研究

研制出新型小周期波荡器，报道三毫米波拉曼自由电子激光器实验。采用Ｉｃｍ周期双绕螺旋线波荡器，在相同加速器能量下，自由电子激光输出波长由８ｍｍ缩短到３ｍｍ。输出功率为１ＭＷ，效率为０．６６％。     

光纤喇曼激光器及多波长输出的分析

为了优化设计光纤喇曼激光器的各项参数,采用喇曼激光器的基本理论模型模拟分析了用DCF光纤做增益介质的光纤喇曼激光器的输出特性,提供了激光器优化设计的方法;通过改变光纤的长度和输出端面的耦合效率得到最优的激光输出;以及改变泵浦功率时输出激光功率的变化情况;并进一步分析了多波长的光纤激光器,得到四波长输出的光纤激光器。     

喇曼自由电子激光器参量测量用法拉弟杯

喇曼自由电子激光器装置所使用的激光工作物质是准直度好、能散度小的脉冲强流电子束,其动能0.5Mev,电流密度几 KA/cm~2。因此测量脉冲强流电子束的参量以及在引导磁场作用下电子束在真空金属漂移管内的传输特性成为建立喇曼自由电子激光装置的重要环节。本文的法拉弟杯正是为了适应实验提出的测量高电流密度脉冲电子束的要求。     

我国康普顿型自由电子激光器获得辐射输出

由上海光机所和中国科技大学合作研制的康普顿型自由电子激光器,于1986年11月1日首次获得辐射输出,辐射波长为10μm。     

纤维喇曼激光器

用掺钕钇铝石榴石激光器和石英丝谐振腔，五位学者除了1.06微米的受激发射外，还观察到1.12微米和1.18微米的强烈的喇曼辐射。类似的工作已由贝尔电话实验室R. H. Stolen, Ravi Κ. Jain和他们的同事作了演示。     

Steady-state stimulated Raman scattering by a multimode laser

The development of the Stokes spectrum and the dependence of Raman gain upon pump laser bandwidth in a narrow linewidth Raman medium are analyzed in terms of a closed set of multimode equations. The analysis predicts that the Stokes gain coefficient takes on its maximum value, which is independent of bandwidth, when the Stokes spectrum replicates the pump spectrum. It is also shown that in the absence of dispersion the spectrum of a weak Stokes wave is driven to duplicate the pump spectrum, and that for noise input the average power generated in the Stokes wave is independent of the pump bandwidth.     

Optical guiding in a Raman free-electron laser

A theoretical and computational study of optical guiding in a Raman free-electron laser (of wavelength ≃ 2 mm) is given. A set of basic dynamical equations is given, including the effects of space-charge and two-dimensional diffraction, both with and without a waveguide. The results from a computer code based on these equations are reported, showing optical guiding. An experiment is proposed in the Columbia free-electron laser to measure optical guiding.     

Regenerative gain in a Raman free-electron laser oscillator

A parametric study of gain in a millimeter-wave Raman free-electron laser oscillator and comparisons to linear theory are carried out. The intense (1 kA/cm²), relativistic (600-800 keV), cold [(deltagamma/gamma)_{parallel} < 1percent] electron beam employed is guided by a 9.45 kG magnetic field through a 1.45 cm period, 49.5 cm long uniform undulator. Operation at < 1 kG pump field results in a < 10 percent electron quiver velocity (upsilon_{perp}/upsilon_{parallel}) velocity. The laser power output has been mea sured at ∼ 3 MW corresponding to an efficiency of 4 percent, and tunability in the 90-170 GHz range has been achieved with a narrow linewidth (Delta lambda/lambda leq 1percent). Using a new technique, linear small-signal growth rates have been unfolded from the oscillator startup delays. Excellent agreement is found with three-dimensional small-signal calculations for both the spatial growth rate and the resonance frequency. One-dimensional theory was found to predict shorter wavelength laser output than that observed.     

Angular distribution of "surface" radiation in stimulated Raman scattering

Anti-Stokes emission in sharply defined cones has been observed from fine filaments in a mixture of acetone with 5 to 10 percent CS2. The cone angle is in agreement with the momentum-matching condition that the longitudinal but not the transverse components sum to zero.     

Short-wavelength stimulated Raman scattering in a silica fiberpumped by an XeBr excimer laser

A UV-grade silica optical fiber was pumped by a 281.8-nm XeBr excimer laser. The first Stokes spectrum was observed at 285 nm. The spectral width was one-half of that of the spontaneous Raman spectrum. A numerical analysis of stimulated Raman scattering which includes two-photon absorption loss is presented. The Raman gain coefficient, determined by an analysis of the nonlinearity observed in the Stokes output, was 1.8×10^-5 cm/MW. The analysis also indicates that two-photon absorption is a more important loss factor than linear attenuation. The short wavelength limit of net amplification by stimulated Raman scattering is estimated to be 272 nm     

Tunable infrared laser generated via stimulated Raman scattering in Cs vapor

The conversion of a visible dye laser output into tunable infrared (IR) laser radiation via stimulated Raman scattering in Cs vapor was investigated. Small-signal gain, threshold intensity, and conversion efficiency measurements were obtained versus pump laser detuning. Fixed-frequency IR outputs at other wavelengths were also observed. One of these, the7P_{3/2}-5D_{5/2}transition, had a strong lasing component polarized perpendicular to the pump laser polarization. Lasing near the 8523-Å resonance line was attributed to a four-wave parametric interaction as a plausible generation mechanism.     

基于受激布里渊散射的可调谐多波长激光器

可调谐多波长布里渊掺铒光纤激光器将光纤中的SBS非线性放大同掺铒光纤的线性放大相结合得到室温稳定的多波长输出,具有波长间隔一致、线宽窄、功率谱相对平坦等优点。设计了一种基于光纤布拉格(FBG)反射的线性可调谐多波长布里渊掺铒光纤激光器。该线性腔激光器的一端利用光纤布拉格光栅作为反射镜,有效抑制了腔内自激模的影响,增加激光器输出波长数。布里渊泵浦信号进入布里渊增益介质之前经过掺铒光纤放大器的两次放大,降低了布里渊增益的阈值。该多波长激光器实现了1 530～1 560 nm之间30 nm可调谐范围的输出。在布里渊泵浦信号功率2 mW,980 nm泵源抽运功率60 mW情况下,1 540～1 554 nm范围内,获得了波长间隔0.088 nm的16个波长的输出。     

高功率光纤激光器受激拉曼散射致模式不稳定研究

通过稳态速率方程和热传导方程建立了高功率光纤放大器热光耦合的有限元模型,利用该模型对受激拉曼散射致模式不稳定效应进行了数值研究。对增益光纤为25/400μm的正向泵浦激光放大器,受激拉曼散射导致激光器信号光高阶模比例上升,当高阶模的比例达到5左右时,模场发生畸变,信号光出现了百毫秒量级的模式耦合,这与实验中观察到光强波动现象一致。本文仿真模型为研究高功率光纤放大器中受激拉曼散射和模式不稳定的关系提供了分析手段。     

Raman spectra and the Los Alamos free-electron laser

Spectra have been obtained of the light generated near 10 μm by the Los Alamos free-electron laser. The spectra contain a main line and copious sidebands, mostly to the long-wavelength side of the main line. The spectra vary in overall width as the detuning parameter is altered or as the sidebands are preferentially allowed to escape the optical cavity. A comparison is made between these measurements and the results of numerical simulations.