Influences of quantum noises on direct-modulated properties of 1.3-μm InGaAsP/InP laser diodes

Due to the zero dispersion point at 1.3μm in optical fibres, 1.3-μm InGaAsP/InP laser diodes have become main light sources in fibre communication systems recently. Influences of quantum noises on direct-modulated properties of single-mode 1.3-μm InGaAsP/InP laser diodes are investigated in this article. Considering the carrier and photon noises and the cross-correlation between the two noises, the power spectrum of the photon density and the signal-to-noise ratio (SNR) of the direct-modulated single-mode laser system are calculated using the linear approximation method. We find that the stochastic resonance (SR) always appears in the dependence of the SNR on the bias current density, and is strongly affected by the cross-correlation coefficient between the carrier and photon noises, the frequency of modulation signal, and the photon lifetime in the laser cavity. Hence, it is promising to use the SR mechanism to enhance the SNR of direct-modulated InGaAsP/InP laser diodes and improve the quality of optical fibre communication systems.     

Influence of the net gain on characteristic of stochastic resonance in a single-mode laser system

The phenomenon of stochastic resonance (SR) is found in a single-mode laser system driven by the colored pump noise with signal modulation and the quantum noise with cross-correlation between the real and imaginary parts. When the net gain a0 changes, it is found that, 1) the shape of the curve of the signal-to-noise ratio (SNR) versus the pump noise self-correlation time τ exhibits a changing process of multiform SR, from single-peak SR, to simultaneous existence of resonances and suppressions; 2) the curve of SNR. versus signal frequency Ω experiences a complicated changing process from the monotonous descending to the simultaneous appearances of a maximum and a minimum, and finally to monotonous descending; 3) the curve of SNR versus cross-correlation coefficient between the real and imaginary parts of the quantum noise λq appears an acute single-peak SR. Therefore, the net gain ao greatly influences the characteristic of SR of laser system.     

STATIONARY PROBABILITY DISTRIBUTION FOR COLORED-LOSS-NOISE MODEL OF A SINGLE-MODE DYE LASER

We apply the interpolation procedure to calculate the stationary probability distribution of the colored-loss-noise model of a single-mode dye laser operating above the threshold with correlation time τ covering a very wide range. By stochastic Runge-Kutta algorithm, we also carry out numerical simulations of steady-state properties. Comparing the results of the interpolation procedure and the unified colored-noise approximation with simulation results, we find that the agreement between the results of the interpolation procedure and the simulation results is much better than that of the unified colored-noise approximation when correlation time τ covers a range from moderate to large. We conclude that the interpolation procedure really improve the accuracy of predictions for this system.     

Intensity Correlation Time of a Single-Mode Laser Driven by Two Coloured Noises with Coloured Cross-Correlation with Bias Signal Modulation

The intensity correlation time T is studied by employing a gain-noise model of a single-mode laser driven by coloured pump noise τ1 and coloured quantum noise τ2 with coloured cross-correlation τ3 with a bias signal modulation. By using the linear approximation method, we detect that a maximum （i.e. resonance） exists in the curves of the intensity correlation time T versus the noise intensities D and Q when the noise correlation coefficient A is positive; and a minimum （i.e. suppression） exists in the T - D and T - Q curves when A is negative. When A is zero, T increases monotonously with increase of D and decreases monotonically with increase of Q. Furthermore, the curve of T versus the pump noise self-correlation time τ1 is also studied. Our study shows that, no matter what the value of A is, there exist one maximum and one minimum in the T - τ1 curve.     

相关色噪声的激光损失模型的定态性质分析

应用近几年发展的处理色噪声的近似方法,计算了具有白联的不同自相关时间的加法色噪声和乘法色噪声驱动的单模激光三次方模型的场幅定态几率分布及其均值、协方差,分析了在阈值上时,激光光强均值和协方差受噪声间的关联强度和噪声的“颜色”的影响。     

单模染料激光色损失模型的定态分析

将加法色噪声驱动的系统的定态几率分布展开理论推广到乘法色噪声系统中，计算了单模染料激光色损失模型的定态几率分布，与Ｐ．Ｊｕｎｇ等用统一色噪声近似所计算的结果相比，本文所得的结果与实验结果要符合得好一些．     

关联色噪声驱动的单模激光的光强关联时间

采用线性化近似,计算了加性信号调制下色泵噪声和色量子噪声驱动的单模激光增益模型的光强关联时间,发现当两噪声间互关联程度λ〈0时,光强关联时间T随量子噪声强度D和泵噪声强度Q的变化曲线中出现极小值（即出现抑制）;当λ≥0时,光强关联时间T随量子噪声强度D和泵噪声强度Q的增加而单调增加．同时还分析了参数r,γ,Ω对’T-D和T-Q曲线的影响,发现当λ〈0时,随着噪声关联时间τ的增大,T-D和T-Q曲线的极小值升高,极小值位置基本不变;随着信号频率Ω的增大,T-D和T-Q曲线的极小值略有增加,极小值位置基本不变;随着衰减系数γ的增大,T-D和T-Q曲线的极小值略有下降,极小值位置基本不变．     

非平衡化学反应界面系统的准热力学分析

本文在几个合理假设下,论证了一个非平衡化学反应流体-流体界面系统在单独流体不失稳的情况下,稳定的界面层化学反应的加入,可以通过耦合使系统呈现一个不稳定区。     

内外噪声驱动下随机系统的关联函数和弛豫时间

本文采用Stratonovich退耦合假设,求出了在内外噪声同时驱动下随机系统的关联函数和弛豫时间.应用到激光系统,得到了内外噪声同时存在时染料激光光强的关联函数和弛豫时间的表达式,为研究染料激光的统计性质提供了有益启示.     

关联噪声驱动下单模激光线性模型的随机共振

根据线性化的单模激光输出光强方程，直接计算光强的相关函数，得到光强的功率谱及信噪比的方法，计算了具有δ函数形式关联的两白噪声驱动的单模激光线性模型在输入信号后其输出信噪比，发现了随机共振现象，根据计算结果讨论了噪声强度和噪声间互关联程度对信噪比的影响，由于推导用的是精确解析表达式，因此所有参数不受限制，可以探讨近似方法适用范围外的规律。