利用杜哈梅尔方法近似求解EDF的自发辐射特性

掺铒光纤(EDF)中的自发辐射噪声是影响掺铒光纤放大器(EDFA)工作性能和掺铒光纤激光器(EDFL)的起振特性的重要因素。自发辐射与泵浦方式紧密相关,研究脉冲泵浦下EDF的自发辐射具有重要的学术意义。从速率方程出发,建立了任意波形脉冲泵浦下EDF自发辐射的能级粒子数分布所满足的一元二阶变系数微分方程。由于没有封闭形式的解析解,采用杜哈梅尔方法,将泵浦脉冲波形进行分时段描述,每个小时段都有解析解,从而得到了自发辐射的平均功率表达式。分析结果表明,随着泵浦功率的增大,ASE的输出波形更接近泵浦光的波形,且泵浦光的毛刺对于ASE噪声的影响较小。     

A modified equation of geodesic deviation

The equation of geodesic deviation is derived under the assumption that the geodesics are neighbouring, but their rate of separation is arbitrary, corresponding, physically, to the relative velocity of two test particles approaching that of light. Some of the consequences of the new equation are discussed.     

双包层掺染料聚合物光纤放大器的增益性能分析

双包层聚合物光纤放大器可以减小染料的热漂白,使用速率方程的方法,给出了一个能够全面描述双包层掺染料聚合物光纤放大器增益性能的模型,模型既考虑了染料三重态能级对速率方程的影响,又考虑了双包层结构对泵浦光的影响,可以在稳态的情况下计算放大器的各种增益性能指标.     

Broad band resonant light pressure

This paper treats the mechanical pressure of resonant light acting on a two-level system, where the degenerate magnetic sublevels are taken into account. The theory is developed with arbitrary relations between the quantization axis and the propagation and polarization of the light. Rate terms are obtained both for spontaneous and induced transitions; the requirements of incoherence put restrictions on the possible geometries of the experiment. The rate equations are restricted to motion along a light beam only; this one-dimensional case is simpler to handle. For small recoil velocities a Fokker-Planck equation is derived, and an adiabatic elimination procedure enables us to derive an equation for the velocity distribution of the total population. The assumptions and approximations are formulated and discussed.     

GaN基多量子阱发光二极管的极化效应和载流子不均匀分布及其影响

制备了GaN基绿光发光二极管.利用耦合法求解了在自发极化和压电极化效应影响下的GaN/InGaN量子阱的极化电场强度.考虑载流子在量子阱间的不均匀分布，模拟计算了系统的一维薛定谔方程、稳态速率方程和泊松方程，得到了载流子在各个阱间的分布比值和辐射复合速率.同时还得到了不同电流下电致发光(EL)谱的峰值波长、谱峰半高宽及EL谱强度的变化情况.发现当测试电流由10 mA 增加到70 mA时，理论结果与实验结果能很好符合. 关键词： 极化 载流子不均匀分布 复合速率     

Optical characteristics of silver-doped polarizing glass

According to the theory of scattering and absorption of light, an anisotropic Ag colloid particle, which is small compared with the wavelength of the incident light, absorbs light differently in different directions. The underlying mechanism is regarded as electron plasma resonance. The optical anisotropy of a single Ag particle or of a group of the same particles has been analyzed. An equation for estimating the distribution of the particle shapes in space is proposed. Based on this equation and the work of other researchers, a program was designed to calculate the major principal transmittance and the minor principal transmittance of Ag-doped polarizing glass. The results show that the polarizing property of glass with particles with different aspect ratios is better than that of glass with identical particles. Also, the effective wavelength range is different if the particles' aspect ratios change, and this range tends to narrow as the parameter R (the rate of change of the aspect ratio) is increased.     

Reverse saturable absorption in tetraphenylporphyrins

A decrease of the light transmission with increasing excitation intensity is observed in tetraphenylporphyrin/toluene solutions irradiated with 80 ps pulses at λ=532 nm. The experimental data are compared with simulations using a rate equation model. Excited state absorption cross-sections are evaluated.     

Degradation behaviors of high power GaN-based blue light emitting diodes

The degradation mechanism of high power InGaN/GaN blue light emitting diodes(LEDs)is investigated in this paper.The LED samples were stressed at room temperature under 350-mA injection current for about 400 h.The light output power of the LEDs decreased by 35%during the first 100 h and then remained almost unchanged,and the reverse current at 5 V increased from 10 9A to 10 7A during the aging process.The power law,whose meaning was re-illustrated by the improved rate equation,was used to analyze the light output power-injection current(L–I)curves.The analysis results indicate that nonradiative recombination,Auger recombination,and the third-order term of carriers overflow increase during the aging process,all of which may be important reasons for the degradation of LEDs.Besides,simulating L–I curves with the improved rate equation reveal that higher-than-third-order terms of carriers overflow may not be the main degradation mechanism,because they change slightly when the LED is stressed.     

铒镱共掺特性对光放大器增益和噪声系数的影响

基于速率方程和光传输方程,对双包层铒镱共掺光纤放大器进行了研究,数值模拟分析了Er3 浓度和Yb3 浓度的变化对光纤放大器增益和噪声系数的影响.结果表明,Er3 浓度较低时,有较好的噪声特性;同时,较低的Yb3 浓度有助于提高增益,并且存在一个增益最大的最佳Er3 浓度值.     

Rate equation approach for diode lasers

The light output and the electron density within the active layer of a semiconductor laser have been calculated from the steady state solution of a rate equation approach. The assumed rate equation model takes into account the spontaneous emission into the lasing modes. Simple analytical approximation formulae have been found under the assumption of a power-law dependence between optical gaing and electron densityn (g ∞n′). The approximations are compared with numerical results from the rate equations. With the exception of a small region near the lasing threshold good agreement has been found. The theoretical results are compared with experimentally measured light outputs from single and double heterostructure lasers. From the comparison below threshold the power law exponent/may be evaluated. The comparison at threshold suggests that the spontaneous emission term decreases at threshold. This decrease is in agreement with experimentally measured changes of the emission bandwidth at threshold.     

Series expansion solution of the Wegner-Houghton renormalisation group equation

The momentum independent projection of the Wegner-Houghton renormalisation group equation is solved with power series expansion. Convergence rate is analyzed for then-vector model. Further evidence is presented for the first order nature of the chiral symmetry restoration at finite temperature in QCD with 3 light flavors.     

半导体激光器型全光波长转换器的啁啾分析

利用速率方程分析了转换信号光的频率啁啾,考虑到了外界注入信号光的放大.转换过程中,信号光的注入将会导致了光腔内载流子数发生变化,进而引起激光器输出频率的改变,产生啁啾.研究发现,较大的激光器注入电流可以有效地抑制频率啁啾,较高的注入信号光功率则可以在保证高转换信号消光比的同时抑制频率啁啾.     

级联双包层铒镱共掺光纤放大器的性能分析

基于速率方程和光传输方程,对级联双包层铒镱共掺光纤放大器（Er3+/Yb3+ co-Doped Fiber Amplifier,EYDFA）进行了研究.数值模拟计算得到级联双包层EYDFA的最佳光纤长度,以及前后向泵浦功率之比和光隔离器位置对于增益以及噪音系数的影响.通过选择合适的前后向泵浦功率之比和隔离器的位置优化级联放大器结构,其增益提高了4 dB,噪音系数降低了近3 dB.     

级联双包层铒镱共掺光纤放大器的性能分析

基于速率方程和光传输方程,对级联双包层铒镱共掺光纤放大器(Er3+/Yb3+ co-Doped Fiber Amplifier,EYDFA)进行了研究.数值模拟计算得到级联双包层EYDFA的最佳光纤长度,以及前后向泵浦功率之比和光隔离器位置对于增益以及噪音系数的影响.通过选择合适的前后向泵浦功率之比和隔离器的位置优化级联放大器结构,其增益提高了4 dB,噪音系数降低了近3 dB.     

用于较大泵浦尺寸半导体泵浦固体激光器的一种特殊腔型

提出一种泵浦固体激光器的特殊腔型,解决了当功率较大时泵浦尺寸较大使得泵浦光斑与激光光斑不匹配的问题,并从激光腔理论和速率方程理论两方面通过数值计算验证了该腔型的优越性.同时对LD泵浦固体激光器以及倍频的设计提出了几条普适原则.     

短谐振腔准分子激光输出的脉冲特性研究

用腔长为7.5cm～20cm的紫外光预电离Blumlein横向放电泵浦XeCl准分子激光器可产生半宽为1.8ns～5ns的短脉冲输出。速率方程的计算机模拟所给出的激光振荡初始尖峰和实验结果做了比较。     

超强线极化激光在e-p等离子体中传播的成丝不稳定性

基于超强线极化激光在正负电子对(e-p)等离子体中的传播方程,讨论了相互作用过程中的成丝不稳定性。得到了电磁波的非线性色散关系和不稳定性增长率,并讨论了传播过程中激光强度和等离子体温度对成丝不稳定性的影响。结果表明,成丝不稳定性的强弱主要由相互作用的非线性效应与受有质动力作用后等离子体密度的减小之间的竞争所决定。     

双稳激光器的不稳定性本质研究

本文从非线性方程稳定性理论出发,给出了双稳激光器速率方程的稳定性三条件,指出了其中两个条件分别是产生双稳和自脉动的不稳定性条件,证明了双稳与光功率曲线出现负斜率的区域相对应,这时小信号分析方程有单调上升解,自脉动则与无稳定解的区域相对应,这时小信号分析方程有振荡上升解。另外两者都属于“三次”非线性现象,但是要在g达到一定的非线性时才可能产生自脉动。 关键词：     

光通信中的功率计算与通信距离等效验证

光通信具有设备体积小、重量轻等优点, 为了保证长距离通信的顺畅进行, 需要对发射功率进行安全系数较高的计算。分析了发射功率、光束发散角和接收灵敏度对系统通信距离与性能的限制。针对光通信中发射功率计算提出了一种安全系数更高的计算公式, 计算公式表明需要求出最小探测功率, 当通信所要求的误码率确定时, 探测器所需最小探测功率可以通过信噪比与接收器所需最小探测功率的关系计算得出, 在实际通信系统中, 探测灵敏度可以测出, 实际通信系统的透过率也可以测出, 探测器所需最小探测功率也可以通过检测得出, 通过实践验证两者结果吻合, 从而验证了发射功率计算公式的可行性。通过计算公式对安全系数最大情况下所能达到的通信距离进行了模拟验证。