线电流摇摆场自由电子激光

根据经典辐射理论计算出电子在线电流摇摆场中运动产生的自发辐射强度分布;利用单粒子理论推导了自发辐射与受激辐射的关系;利用这种关系求出了电子在线电流摇摆场中运动产生自由电子激光的小信号增益。     

用自由电子激光产生高次谐波

布鲁克海文国家实验室与阿贡国家实验室已演示一种高增益谐波产生自由电子激光器 ,他们希望它能导致发展出硬 X射线激光。其原理论证实验已有叙述 ,在布鲁克海文用一 0 .5MW CO2 激光的 2 0 0 ps1 .0 6 μm脉冲作种籽脉冲。种籽脉冲在一次波荡器与 4 0 Me V电子束相互作用 ,产生能量调制。色散磁铁将此能量调制转化为相干空间密度调制 ,在第二波荡器产生 5.3μm相干光。研究者计划用 Ti∶宝石激光器的 2 6 6nm的三次谐波作种籽 ,输入该装置 ,产生真空紫外光。进一步的实验可使用更多的增益级 ,使输出提高至 X射线区。用自由电子激光产生…     

等离子体尾波场摇摆器自由电子激光

自由电子激光的小型化和实现激光短波长一直是自由电子激光领域的研究热点,而短周期、强场摇摆器是解决此问题的行之有效的途径。文章分析了利用等离子体尾波场作为自由电子激光摇摆器的机制,推得自由电子的自发辐射谱,利用麦迪定在线阵列理论求得电子的受激辐射公式,得到小信号增益。     

加反向导引场自由电子激光动力学理论

本文对加反向导引场自由电子激光加以描述，假定摇摆场是理想化的，分析电子的运动轨道，解得运动常数，求解符拉索夫方程得到扰动分布函数，从波方程可得色散关系，进而得增益公式，该公式近似适用于有导引场和无导引起的情况。     

电子在双曲函数摇摆场和轴向导引场中的运动分析

本文用扰动法来分析电子在具有双曲函数型摇摆场和轴向导引场中的离轴运动轨道和速度。发现了电子运动存在着丰富的回旋谐振频谱，有基波即磁共振和高次谐波回旋谐振和反回旋谐振，并且存在分数谐振和反谐振。     

静电摇摆器自由电子激光的自发辐射

基于静电摇摆器中电势场的一种典型二维模型 ,在小振幅振动情况下讨论了相对论电子束在其中的运动规律 ,计算得到了该类型自由电子激光的自发辐射谱。上述结果与平面磁摇摆器有类似的形式     

1994年底长波自由电子激光

简短总结了长波自由电子激光的现状及其未来最重要的发展方向，为讨论方便，长波是指波长长于０．５ｍｍ。长短波间的区发并非完全随意。它们具有不同的物理过程。例如，长波中主要彩和强流电子束，因而空间电荷效应变得很重要。诚然，其主要相互作用机制通常是相干拉曼散射，而不是相干康普顿散射。另外，波长较长时，由漂移管及腔中电子束的 效应及有限横向尺寸导致的色散效应将变得重要。长波自由电子激光研究的最终目标是建立总     

Theory of a free-electron laser with a Gaussian optical undulator

A theoretical study of the possibility of a free-electron laser in the XUV and soft X-ray region of the spectrum, using a counterpropagaing CO₂ laser beam as an undulator, is presented. A one-dimensional model is used to evaluate the single-pass power gain of such a device. The detrimental effects due to the energy speed, emittance of the electron beam, and the diffraction of the electromagnetic undulator are explicitly incorporated in the formalism. An oscillator experiment is also considered. The solutions of the optical pulse evolution equation in the weak field, low gain, and long-electron-pulse regimes are all derived     

Influence of a step-tapered undulator field on the optical pulseshape of a far-infrared free-electron laser

The optical output of the free-electron laser for infrared experiments (FELIX), which operates in the regime of strong slippage, consists of picosecond pulses. Depending on the amount of cavity desynchronization, the optical pulse can develop substantial structure in the form of multiple subpulses. We present second-order autocorrelation measurements of the subpulses at several far-infrared wavelengths while applying a step-taper in the undulator field. The operation with a step-tapered undulator prevents the electrons from reabsorbing the optical field energy, leading to a smooth optical pulse. For different settings of the undulator the measured pulse shape and corresponding power spectrum are discussed. It is possible without decreasing the small-signal gain to produce a smooth high-power optical pulse during the whole saturated part of the machine pulse in an FEL oscillator with a reverse-step tapered undulator     

Short-pulse effects in a free-electron laser

The Free-Electron Laser for Infrared eXperiments (FELIX) offers a unique combination of short electron bunches and long wavelengths, i.e. a slippage parameter μ_c ranging up to 10. As a consequence, pronounced short-pulse effects can be observed. In this paper the experimental observation of two of these effects is discussed, namely the occurrence of limit-cycle oscillations and the feasibility of tuning of the micropulse duration. The stable limit-cycle oscillation of the macropulse power is due to a modulation of the optical micropulse shape. This is a consequence of a combination of high optical power and short pulses. The former causes synchrotron oscillations of the electrons and the effect is, therefore, closely related to spiking phenomena. The short-pulse nature of FELIX ensures that the oscillations do not evolve into the chaotic behavior normally associated with spiking and the sideband instability. Experimental results are compared with numerical simulations     

组合式二维列阵面发射半导体激光器

设计出新型二维列阵面发射激光器,获得了室温准连续大于250mW的光功率输出。     

乙烯分子在激光场中的多光子电离及高次谐波的产生

本文运用含时密度泛函理论和局域密度近似方法,分别研究了乙烯分子在单色激光场、双色激光场中电离和高次谐波的产生。计算结果表明,在单色激光场中,乙烯分子的高次谐波谱呈现出明显的平台区和奇次谐波加强的特征：在双色激光场中,乙烯分子的电离增强而出现高电荷态几率,并伴有偶次谐波的出现。     

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.     

Nonlinear theory of a quadrupole free-electron laser

The nonlinear motion of electrons in a quadrupole free-electron laser is analyzed. If the betatron frequency is close to the mismatch frequency, the three-dimensional nonlinear equations can be reduced to an integrable one-dimensional equation. To enhance the efficiency, a tapered wiggler is introduced and the electron orbits in a tapered quadrupole free-electron laser are analyzed. The conditions for the particles to remain trapped as the heat wave decelerates are found.     

AM mode-locking of a free-electron laser oscillator

The authors present experimental and theoretical studies of a mode-locked free-electron laser (FEL) oscillator. In the experiment the FEL uses a continuous electron beam and operates in the microwave regime. AM mode-locking is performed by modulating the attenuation of the FEL ring cavity by a PIN diode modulator. The modulation period is tuned to match the RF roundtrip time in the ring cavity. The experimental results show the evolution of a single radiation macropulse, consisting of narrow micropulses in synchrony with the sinusoidal locking signal. The micropulse period (~37 ns) equals the roundtrip time and the modulation period. The micropulse width (~5 ns) is limited by the FEL slippage time and by the dispersion in the waveguide ring cavity. The effect of the mode locking consisting in suppressing asynchronous oscillations is clearly observed in the experiment. A theoretical model of the AM mode-locked FEL oscillator operating in the small signal regime is presented. This model includes the slow time variation of the e-beam energy and waveguide dispersion. The theoretical analysis agrees well with the experimental results     

Simulations of a ring resonator free-electron laser

A relatively high gain (≈25 to 40%) free-electron laser (FEL) with an optical ring resonator is simulated using the code FELEX. The laser system corresponds to the `burst mode' FEL. The ring consists of paraboloids, grazing incidence hyperboloids, and a grating rhomb. The wiggler is 5 m in length and has an adjustable taper, while the electron beam is produced by an RF linac. The optical elements of the ring together with the FEL interaction in the wiggler are modeled in three spatial dimensions to investigate the system from start-up to saturation. Both single-frequency and finite-pulse simulations are performed     

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.