面电流摆动器与线电流摆动器自由电子激光理论

从电子轨迹的相似性出发，用类比的方法得到了面电流摆动器和线电流摆动器自由电子激光的自发辐射谱；然后用单粒子理论推导出了自发辐射与受激光辐射的关系，根据这种关系求出了两种电流摆动器自由电子激光的小信号增益。     

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。     

自由电子激光中自发辐射光脉冲的自干涉现象

本文用格林函数法,计算了螺旋磁场自由电子激光中单脉冲电子注的自发辐射;结果表明,电子注的有限长度会引起自发辐射光脉冲的自干涉现象。     

二维摆动磁场自由电子激光自发辐射的频谱特性

本文对二维摆动磁场自由电子激光的自发辐射频谱进行了理论分析,并对分析结果进行了数值计算.计算结果表明,采用l(lkx=ky)值不同的二维摆动磁场,可以增强第l次谐波的自发辐射强度,从而能够有选择地实现自由电子激光的高次谐波运转.     

真空紫外和X射线自由电子激光器

直线加速器的最新进展，激光驱动低发射度电子枪的新发展和超高精度长摆动器的可行性，开创了以自放大自发辐射（SASE）为基础建立单程自由电子激光器（FEL）的可能性。这种自由电子激光器有可能在真空紫外和X射线区提供极强，偏振、超短脉冲的辐射。除了它们的高峰值亮度和平均亮度，光子能量的可调谐性和辐射的横向相干性都将使这种自由电子激光器成为无可匹敌的光源。关于真空紫外和X射线自由电子激光器世界范围的几项课题已经启动。汉堡德国电子同步加速器（DESY）的真空紫外自由电子激光器（VUV-FEL）上，首次在真空紫外区观察到激光发射。讨论了以自放大自发辐射为基础的自由电子激光器工作原理及元件；提出了克服统计起伏和增加纵向相干性的方案，给出了与这种自由电子激光有关的基础研究和应用研究例子。     

二维摆动磁场自由电子激光自发辐射的频谱特性

本文对二维摆动磁场自由电子激光的自发辐射频谱进行了理论分析，并对分析结果进行了数值计算。计算结果表明，采用ｌ（ｌｋ２＝ｋｙ）值不同的二维摆动磁场，可以增强第ｌ次谐波的自发辐射强度，从而能够有选择地实现自由电子激光的高次谐波运转。     

磁场与z轴无关摆动器自由电子激光的自发辐射与受激辐射

本文讨论了磁场与z轴无关摆动器自由电子激光中的能量损失和能量离散以及它们相应的意义.分析、计算了自发辐射和受激辐射.结果说明:自发辐射正比于电子能量离散;光功率增益正比于平均电子能量损失.     

有轴向磁场的平面摆动器自由电子激光

研究了电子在有同向磁场的平面摆动器中的自发辐射和谐波相干辐射，得到了一个较普遍的自发辐射谱表达式和谐波自由电子激光的增益。当电子的能量较高或者沿摆动器轴线观察时，辐射是椭圆极化的，适当附加轴向磁场，可以提高激光增益，对于较低次谐波，增益提高更明显。     

两维摇摆场自由电子激光的谐波特性研究

本文应用Nadey定理对两维摇摆场自由电子激光的谐波特性进行了研究。导出了这种新型摇摆场结构自由电子激光高次谐波的自发辐射功率密度和小信号增益公式。以及电子与辐射场的耦合系数的表达式。计算结果表明,采用两维摇摆场可以增强电子与辐射场之间的耦合,提高谐波的辐射强度和增益。而且在某些条件下,在轴上既可获得奇次谐波又可获得偶次谐波。     

软X射线自由电子激光试验装置微波系统

软X射线自由电子激光装置(SXFEL)是中国第一台X射线相干光源,其最短波长可达到2 nm.这台基于1.5 GeV的C波段高梯度电子直线加速器的激光装置分试验装置(SXFEL-TF)和用户装置(SXFEL-UF)两个阶段进行研制,最终形成包含1条种子型自由电子激光束线、1条自放大自发辐射束线以及5个实验站的用户装置.试...     

Non-white photodetection noise at the output of an optical amplifier: theory and experiment

Based on the statistical properties of amplified spontaneous emission, the photodetection noise spectrum at the output of an optical amplifier is calculated. The results revealed that the signal-spontaneous emission beat noise spectrum is a transposition of the spontaneous-emission spectrum to the low-frequency domain, and the spontaneous emission-spontaneous emission beat noise spectrum is the auto-correlation function of the spontaneous-emission spectrum. These theoretical results are verified experimentally on an erbium-doped fiber amplifier, filtered by a Mach-Zehnder interferometer.     

Sideband evolution from spontaneous into amplified emission in a free electron laser

A theoretical study of the evolution of sidebands, originating from large-scale (nonlinear) oscillations in the electron dynamics, is reported for a combined wiggler and guide field system operating near magnetoresonance. These sidebands, already existent in the spectrum of spontaneous emission, are followed up through small signal gain computations, and are finally recovered in the simulations of the nonlinear saturation process. A comparison with a radiation spectrum of an experiment done at the Naval Research Laboratory (NRL) shows good agreement. This indicates that the sidebands, observed in the experiment at saturation power level, are essentially due to the specific structure of the spectrum of spontaneous emission.     

Analysis of the spontaneous emission of a tunablephase-shift-controlled DFB laser filter

Using a transfer matrix method, the results of analysis of the spontaneous emission spectrum of a three-section phase-controlled distributed feedback (DFB) laser for implementing a continuously tunable optical filter are presented. The influence of various parameters-net field gain, coupling coefficient, phase shift and reflection coefficients-on the spectrum behavior are studied theoretically. The main-to subtransmission peak magnitude ratio can be chosen while varying the frequency, which demonstrates the tunability of the three-section phase-controlled DFB laser filter. Analysis shows that a three-section DFB laser (a passive phase shift control region between two DFB structures) presents a single-mode spontaneous emission spectrum operating over a wide continuous tuning range of less than 1 nm     

Determination of Internal Loss and Quasi-Fermi Level Separation From the Amplified Spontaneous Emission Spectrum of Fabry–PÉrot Semiconductor Lasers

The net modal gain and the un-amplified spontaneous emission (ASE) coupled into the laser waveguide mode are extracted from the ASE spectrum of Fabry–PÉrot semiconductor lasers by the Fourier transform method with a deconvolution process. Highly accurate quasi-Fermi level separation and internal loss are then derived by a minimum search process from the relationship between the spontaneous emission and gain.     

Theory of timing jitter in actively mode-locked lasers

An analysis of the pulse-to-pulse timing jitter in an actively mode-locked laser is presented. The model includes spontaneous emission noise, mode-locker driver phase noise, and cavity length detuning. Analytical expressions for the laser pulse train phase noise spectrum, the intensity power spectrum, and the RMS timing jitter are given. The timing fluctuations are characterized by a time constant proportional to the cavity round-trip time times the number of locked modes squared divided by the modulation depth. The contribution from the mode-locker driver phase noise will dominate unless high-stability RF sources are used. The residual timing jitter due to spontaneous emission noise is very sensitive to cavity detuning     

Low-temperature electroluminescence from an ordered nanopore array diode laser

We report the first study of spontaneous emission from an ordered nanopore array diode laser at 77 K. The presence of gaps in the spontaneous emission spectrum supports the theoretically predicted formation of a subband structure in the valence and conduction bands.     

Quantum theory of spontaneous emission from a two-level atom in aone-dimensional cavity with output coupling

A nonperturbative fully quantum-theoretical analysis describing the transient spontaneous emission of an initially excited two-level atom in a one-dimensional cavity with output coupling is presented. A delay-differential equation for the probability amplitude of the upper atomic state is strictly derived from the Schrodinger equation. With this equation, both the time evolution of the atomic state and the emission spectrum are calculated. Furthermore, the mode function makes the calculations of emitted fields both inside and outside the cavity possible. The calculated result of the vacuum Rabi oscillation in an underdamped cavity and the result of enhanced spontaneous emission rate in an overdamped cavity are presented. A retardation-governed revival of the upper atomic state is predicted. The calculated results also show the inhibition of spontaneous emission by detuning or by setting the atom at a node     

Bit-error rate of lightwave systems at the zero-dispersionwavelength

The author derives approximate expressions for the bit-error rate of very long lightwave systems with optical amplifiers that are operated at the zero-dispersion wavelength. In this case, the nonlinear interaction of the signal wave with the spontaneous emission noise of the amplifiers corrupts the signal. Its spectrum broadens by several orders of magnitude, and the instantaneous optical power assumes the appearance of bandlimited thermal or spontaneous emission noise. This observation suggests that the bit-error rate should be computed under the assumption that the optical signal and the optical spontaneous emission noise obey Gaussian statistics. The approximate expressions for the bit-error rate are derived under this assumption. The formulas are written in such a way that the signal and the noise may be either completely polarized or completely unpolarized     

Direct observation of the spatial hole burning and the saturation of the spontaneous emission in InGaAsP/InP lasers

The saturation behavior of the spontaneous emission intensity from a diffused-stripe InGaAsP/InP laser is studied. In InGaAsP/ InP DH lasers, a spontaneous emission can be observed through the InP substrate without any optical loss. The spatial distribution and the spectrum of the emission were directly observed from the substrate surface. The spatial hole burning was observed in the wider stripe lasers but in the case of narrow stripe lasers, the spontaneous emission almost uniformly saturates. The spectrum of the emission from the center of the narrow stripe lasers was analyzed and it was confirmed that, above the threshold current, the spectra in the lasing region saturated over the entire spectral region.     

Amplified spontaneous emission and carrier pinning in laser diodes

Theoretical and experimental results for the temperature dependence of amplified spontaneous emission (ASE) in laser diodes (LDs) and light-emitting diodes (LEDs) are presented. The theoretical model takes into account conduction band nonparabolicity and band-gap renormalization. The gain spectrum is calculated from the theoretical spontaneous emission spectrum, and both compare very well with experimental data. From a fit to the observed temperature dependence of ASE for an LED and the gain spectrum for an LD with a structure identical to that of the LED except for mirror reflectivity, it is possible to establish carrier density as a function of injection current for both devices. It is shown that photons fluctuating into cavity modes give rise to substantial subthreshold carrier pinning in laser diodes. These fluctuations extract an extra current from the device and play an increasingly important role with increasing temperature