EFFECTS OF COLOURED NOISE IN A TWO-MODE LASER SYSTEM

A homogeneously broadened two-mode laser system with multiplicative coloured noise is investigated when the mode coupling constant ξ=2. An analytical result is obtained when two-dimensional decoupling theory is applied to the system. The intensity auto-correlation function and effective eigenvalue of the laser system are calculated when the difference of pump parameters, multiplicative noise strength and noise correlation time are varied. It is shown that the multiplicative noise can enhance the fluctuations while the noise colour can reduce the fluctuations in the laser system.     

Stochastic resonance in a bistable system with coloured correlation between additive and multiplicative noise

The phenomenon of stochastic resonance (SR) in a bistable nonlinear system with coupling between additive and multiplicative noises is investigated when the correlation between two noise terms is coloured. It is found that the signal-to-noise ratio (SNR) of the system is affected not only by the coupling strength λ between two noise terms, but also by the noise correlation time τ. The SNR is changed from a single peak, to two peaks with a dip, and then to a monotonically decreasing function with noise strength. The dependence of the SR on the initial conditions is entirely caused by the coupling strength λ between two noise terms.     

分化与整合:加速转型期中国社会稳定性分析

 当前我国社会正处在加速转型期“社会转型(socialtransformation)”一词来源于西方发展社会学理论和现代化理论。“转型”是社会学家对生物学概念的借用。在生物学中, transformation为生物演化论, 是指“微生物细胞之间以‘裸露的'脱氧核糖核酸的形式转移遗传物质的过程”, 特指一物种变为另一物种。[1]西方社会学家借用此概念来描述社会结构具有进化意义的转变。     

GENERAL SYNCHRONIZATION OF CHAOS IN A SYSTEM OF TWO NON-IDENTICAL LASERS

General synchronization of the chaotic intensity fluctuations of two spatially coupled Nd:YAG lasers with pump modulation is investigated theoretically when the losses of the two lasers are different. It is shown that the chaotic synchronization still exists for medium coupling even though the two lasers are different. For strong coupling the system shows periodic motion of laser intensities. While for weak coupling, the two lasers oscillate independently. It is obvious that the increase of difference between the two lasers reduces the degree of chaotic synchronization.     

倍增噪声和饱和效应对环形激光场动力学性质的影响

用一椎近似的方法求得了同时存在倍增噪声和饱和效应的双向环形激光场含时几率密度函数,讨论了倍增噪声和饱和效应对表征激光场动力学性质的两个重要物理量－－光场强度相关时间和有效本征值的影响。     

噪声之间的正负耦合对激光场的影响

从理论上对加性噪声和倍增噪声之间有耦合作用的一维激光模型进行了分析，发现耦合的性质对激光场涨落影响较大，噪声之间的正耦合会延缓强度相关函数的衰减，增强激光系统的统计涨落。噪声之间的负耦合能抑制激光系统的统计涨落，提高激光场的相干性，使激光系统由随机过程向确定过程过渡。     

EFFECTIVE EIGENVALUE FOR THE INTENSTTY CORRELATION OF A LASER WITH MULTIPLICATIVE WHITE NOISE

Exact formulas of the effective eigenvalues in a single - mode laser with multiplicative white noise are derived through the full saturation laser model and the third order laser model . Compared with the numerical computations and the. experimental measurements, excellent agreement is obtained for the full saturation theory, and hence the cavity decay rate for the experimental electric field can be concluded easily. Relatively large, errors occur in the third order theory and the measured data.     

定态双向环形气体激光中的饱和效应

从理论上分析了双向环形气体激光中的全饱和效应，导出了定态激光强度分布函数的解析形式，算出了定态双模强度的自相关和相相关函数。与激光的三次模型 实验测相比较，激光的全饱和模型与实验测量符合更，而三次模型的结果偏差较大。     

双模气体激光中的背散射和饱和效应

本从到理论上分析了双向环形气体激光中背散射和饱和效应的作用，导出了用相背散射时定态双模激光强度分布函数的解析解，求出了强度相关的有效本征值。与实验测量相比较，具有背散射的全饱和激光模型与实验吻合得最好，而其他激光模型偏差较大。     

STRONGLY COLORED NOISE IN THE DYE LASER FAR ABOVE THRESHOLD

The intensity fluctuations of a single mode dye laser is investigated when the laser is operated far above threshold. The analytic result of the laser intensity correlation function is obtained when both the additive white and strongly multiplicative colored noise are included in the laser model. The analyses show clearly the dependence of the intensity fluctuations on the strength and time scale of the pump noise.