啁啾脉冲激光通过钛宝石放大介质传输特性研究

从非线性薛定谔方程出发,运用分步傅立叶变换(FFT)算法,研究了啁啾脉冲激光在钛宝石放大介质中的传输和放大特性,详细讨论了放大介质的增益饱和与增益窄化效应,以及光束的波前位相畸变对输出脉冲时空特性的影响。     

啁啾脉冲激光放大器输出光束时间特性的理论和数值模拟

利用分布傅里叶变换对描述啁啾脉冲放大的非线性薛定谔方程进行求解 ,研究了在钕玻璃和钛宝石这两种增益介质中 ,自相位调制、增益变窄和增益饱和这三种非线性效应对放大啁啾脉冲输出特性的影响 ,具体给出了在不同放大介质中 ,它们对放大脉冲的影响程度和影响结果。重点阐明了自相位调制对放大啁啾脉冲的影响 ,及其与另外两种非线性效应的内在联系     

克尔效应在超短脉冲放大中的影响

从麦克斯韦方程组出发,在考虑了克尔放大介质的增益饱和、增益谱、群速度色散和克尔效应后,建立了描述超短光脉冲在激光放大介质中传输特性的物理模型。运用分步傅里叶变换法,得到了表征克尔效应强弱的B积分及其对光脉冲产生的频率啁啾。最后讨论了克尔效应对光脉冲形状和频谱的影响。     

光孤子在分布式光纤放大器中传输特性的研究

光纤放大器用于补偿光信号在光纤中的传输损耗,是全光通信网中的核心器件。建立了光孤子在分布式光纤放大器中传输的物理模型,采用分步傅里叶变换法数值模拟了光孤子的传输放大特性,讨论了增益色散对光孤子形状和频谱的影响。结果表明：在放大器的反常色散区,随着光孤子的放大,会不断地产生啁啾孤子,孤子频谱会加宽并且产生振荡结构。放大介质的增益色散将会使光孤子幅度下降,宽度展宽,频谱窄化。因此,光纤放大器的色散、非线性效应和增益色散均会对光孤子的传输特性产生影响。     

掺镱光纤激光器的多波长振荡特性

利用Sagnac梳状滤波器,研究了环形腔掺镱光纤激光器(YDFL)在室温和77 K时的多波长振荡行为。结果表明,在室温和77 K时,掺镱光纤(YDF)均呈现明显的非均匀加宽效应,使得掺镱光纤激光器的起振波长数随抽运光功率的提高而增多。但在室温下,因均匀加宽效应强,掺镱光纤增益的非均匀加宽并不能补偿其内禀不平坦的增益谱,造成波长缺失现象,且当波长间隔减小至0.8 nm时,均匀加宽效应引起的波长竞争造成了多波长振荡的稳定性下降。而在77 K时,掺镱光纤非均匀加宽效应明显增强,在0.8 nm的波长间隔下,无波长缺失现象,将起振波长数增加到32个,且多波长振荡稳定。     

频率失谐对掺镱光纤放大器中光脉冲传输特性的影响

为了研究光脉冲在掺镱光纤放大器中的放大传输特性,建立了光脉冲在分布式光纤放大器中的传输方程,采用分步傅里叶变换法数值模拟了光脉冲的传输状态,并着重讨论了频率失谐对光脉冲特性的影响。结果表明：对于掺镱光纤放大器,在介质的色散长度远远小于非线性长度时,随着在放大器中的传输,光脉冲在放大的同时被展宽,脉冲中心出现峰值,其频谱加宽;当出现频率失谐时,光脉冲放大能力减弱,脉冲失去对称性,并且窄化。若光脉冲中心频率沿不同的方向偏离介质增益峰值频率,脉冲变形规律不同。因此在设计放大系统时应该考虑光纤放大器的色散以及频率失谐对其传输特性的影响。     

光子晶体光纤中非线性自陡峭对高阶孤子传输的影响

采用对称分步傅里叶法数值模拟了高阶孤子在自陡峭效应的影响下,脉冲传输特性及脉冲和频谱展宽情况.另外,讨论了存在自陡峭的情况下,初始正啁啾在反常色散区,导致脉冲初始窄化,然后脉冲将有较强的展宽.初始负啁啾加强脉冲展宽.     

半导体光放大器中SPM效应对光脉冲传输性能的影响

为了研究半导体光放大器（SOA）中自相位调制（SPM）效应对光信号传输性能的影响,从SOA中光脉冲的传输方程出发,采用数学推导的方法,分析了SPM 效应的产生机理,得到了光脉冲经SOA 放大后的时域和频域变化特性,并针对无啁啾和带啁啾光脉冲两种情况进行了仿真研究。结果表明:SPM 导致了光脉冲时域波形的倾斜和频谱的红移,并且随增益的变大倾斜和红移的程度增强;啁啾系数的符号决定了频谱是红移还是蓝移。     

脉冲啁啾对相位共轭通信系统性能的影响

数值模拟了线性啁啾高斯脉冲在光纤中的传输演化过程,分析了线性啁啾高斯脉冲的传输特性。结果表明,脉冲啁啾不会影响中置相位共轭系统对色散和非线性效应导致的信号失真的完全补偿;单模光纤中啁啾将导致脉冲信号产生初期窄化和末期窄化过程,这种传输特性可用来优化相位共轭系统的总体结构设计,进一步改善和提高系统的补偿性能。     

宽带光再生放大幅度调制效应的研究

根据宽带激光在均匀加宽线型增益介质中的放大理论模型,采用短时傅里叶变换算法数值模拟了相位调制的光脉冲通过再生放大器传输放大后的时间波形,分析了再生放大过程中各个参数对幅度调制效应的影响。计算结果表明,调节光脉冲中心波长使之与增益介质中心波长匹配,提高注入种子脉冲的能量都能够有效地降低再生放大器中的幅度调制效应,提高光束质量。     

Active mode locking with hybrid lasers

We present the results of a numerical study of active mode locking with hybrid lasers which contain an inhomogeneously broadened laser medium and an homogeneously broadened laser medium. The spectral, pulse, and gain characteristics of actively mode-locked hybrid lasers and the influence of the unsaturated gain, the saturation power, and the homogeneous linewidth on the pulse coherence and bandwidth are studied. The simulations show that coherent and shorter pulses are generated as compared to that by either an inhomogeneously broadened medium or a homogeneously broadened medium alone. Varying the unsaturated gain or the saturation power of the gain medium are two equivalent ways to obtain the same maximal coherent pulse bandwidth for given gain media. When different gain media can be selected, a larger pulse bandwidth can be obtained with the use of a broadband homogeneously broadened medium     

高增益激光的饱和效应和最佳输出耦合

本文在均匀和非均匀谱线加宽情况下,计算了高增益介质在不同小信号增益系数和吸收系数下的激光输出特性,并讨论了饱和效应和最佳输出耦合。     

Continuous-wave lasing of hybrid lasers

The continuous-wave (CW) lasing of hybrid lasers, which contain a broad-band inhomogeneously broadened laser medium and a narrow-band homogeneously broadened laser medium in a single cavity, is analyzed theoretically. The interactions of the laser modes and two gain media are solved self-consistently using the coupled rate equations. The spectral, gain, and power characteristics under different gain conditions are simulated. It is shown that a small gain from a second narrowband laser medium can effectively shape the lasing spectrum and improve the spectral concentration of the hybrid laser. The total saturated gain profile of the hybrid laser is relatively smooth, due to saturation of the gain of the narrow-band medium to a smaller and below-threshold level     

Theory of line narrowing and frequency selection in an injection locked laser

We apply the multimode semiclassical laser theory to the problem of line narrowing and frequency selection in an injection locked laser. Our goal is to predict from the spectroscopic properties of a given active medium, the behavior of a broad-band laser that is under the influence of a narrow-band injected signal. Analytic expressions for the injected signal strength necessary for single-mode operation are obtained for both homogeneously and inhomogeneously broadened lasers, and for small-signal and strong-signal regimes. We found that under certain experimental conditions, an injection locked inhomogeneously broadened laser behaves significantly different from a homogeneously broadened lasel.     

Device characteristics of long-wavelength lasers based on self-organized quantum dots

The current state of the field of semiconductor lasers operating in the spectral range near 1.3 ??m and with an active region represented by an array of self-organized quantum dots is reviewed. The threshold and temperature characteristics of such lasers are considered; the problems of overcoming the gain saturation and of an increase in both the differential efficiency and emitted power are discussed. Data on the response speed under conditions of direct modulation and on the characteristics of lasers operating with mode synchronization are generalized. Nonlinear gain saturation, the factor of spectral line broadening, and the formation of broad gain and lasing spectra are discussed.     

Saturation effects in semiconductor lasers

This paper describes a theory for a semiconductor active medium interacting with a laser field. In a semiconductor laser, the charge carrier transitions are inhomogenously broadened, and electron-electron and electron-phonon collisions tend to dephase the laser transitions and maintain thermal equilibrium among the carriers. These properties cause semiconductor lasers to frequency tune as though they are inhomogeneously broadened and to saturate as though they are homogeneously broadened. A theory that contains these two aspects of semiconductor laser behavior is presented. From it, we are able to calculate the loaded gain, efficiency, intensity, and carrier-induced refractive index of a semiconductor active medium.     

Intracavity shaping of mode-locked laser pulses

A laser synthesizer of optical pulses is proposed. It is based on injection locking of numerous weakly coupled laser oscillators with a common resonator. A proper shaping of the susceptibility through shaping the pump beam reduces the dispersion of all orders due to the resonance transition and leads to generation of pulses close to the inverse bandwidth of the gain medium. A simple intracavity shaping mechanism allows synthesis of higher-order time supermodes directly from the laser. This technique could be applied to both active and passive mode-locked lasers with homogeneously and inhomogeneously broadened transitions. The possibility of using a compound gain medium is also discussed     

Dispersion-induced instability in CW laser oscillators

A CW-pumped laser with a short photon cavity lifetime may show an unstable output in the form of spontaneous pulsations or noise. In this paper, a model is developed which reconciles previous studies of unstable behavior in homogeneously and inhomogeneously broadened lasers. Specific regions of instability are predicted for xenon lasers, and it is concluded that some degree of inhomogeneous broadening makes the instability much more likely to be observed.