一种新的光学合成孔径系统成像性能指标与光瞳优化方法

为探索能够准确反映合成孔径系统成像性能的特征指标,计算比较了三种典型的六孔径阵列的填充因子上下限、截止频率、截止能量比以及相关系数等参数,发现其成像质量主要与调制传递函数(MTF)中低频段的频谱分布有关。在此基础上,提出了综合考虑频率高低与频段分布均匀性的加权频段能量曲线,可以较准确地反映不同阵列在成像质量方面的差异。为实现MTF中低频段频谱能量最大化,对三种阵列的光瞳结构进行优化,得到对应的中心聚合型阵列。实验结果表明,新阵列在成像质量上明显优于原阵列,填充因子范围也能满足一般设计需求。     

周期外力对频率涨落的过阻尼谐振子所作的功和能量随机共振

研究了周期外力对频率涨落的过阻尼谐振子系统作功的特点. 结果揭示了瞬时功率随时间的周期变化出现不对称性. 研究结果还揭示周期外力一个周期对系统所做的功随乘法噪声强度的变化出现非单调行为, 系统是否出现能量随机共振与抑制并存, 由乘法噪声与加法噪声之间互关联的符号决定. 关键词： 过阻尼谐振子 频率涨落 周期外力作功 能量随机共振与抑制     

Stochastic resonance of a damped oscillator with frequency fluctuation driven by a periodic external force

<正>Considering a damped linear oscillator model subjected to a white noise with an inherent angular frequency and a periodic external driving force,we derive the analytic expression of the first moment of output response,and study the stochastic resonance phenomenon in a system.The results show that the output response of this system behaves as a simple harmonic vibration,of which the frequency is the same as the external driving frequency,and the variations of amplitude with the driving frequency and the inherent frequency present a bona fide stochastic resonance.     

单模激光系统中信噪比对净增益的随机共振

研究了受信号调制的色泵噪声和实虚部间关联的量子噪声驱动的单模激光系统的随机共振现象,发现信噪比随激光系统净增益系数存在随机共振.当泵噪声自关联时间和调制信号频率增加时,信噪比随激光系统净增益系数的变化曲线经历了从同时出现共振和抑制到单调上升的演化过程;当调制信号振幅、泵噪声强度和量子噪声强度、量子噪声实虚部间关联系数等变化时,该曲线一直同时出现共振和抑制,但共振峰和抑制谷有很大的变化.     

New amplitude equation of single—mode laser

The white-gain model and the white-loss model of a single-mode laser are investigated in the presence of cross-correlations between the real and imaginary parts of quantum noise as well as pump noise. It was found that, like the white cubic model (2001 Chin. Phys. Lett. 18 370), the amplitude equations are all decoupled from the phase equations for the two models, and the same novel term appears in the amplitude equations of the two models. So we can put the amplitude equations of all the models into a general form, that is, the new amplitude equation. We further use this new amplitude equation to study specifically the stationary properties of the laser intensity for the white-gain model.     

Modulated stochastic multiresonance in single-mode laser system without input periodic signal

The stochastic resonance phenomenon in a single-mode laser system driven by multiplicative and additive Gaussian white noises without external periodic force is studied. We find that there are multiple extrema (maximum) in the curve of the mean output laser intensity versus the logarithm of multiplicative noise level. This phenomenon reveals that the mean output laser intensity can be amplified at several values of the multiplicative noise intensity, whose peaks are likely modulated by a sinusoidal function.     

具有频率涨落的简谐力激励下线性谐振子的随机共振

针对线性谐振子受到具有频率涨落的简谐力激励的情况, 计算出系统响应的一阶矩解析表达式.研究发现系统的输出响应以固有频率振动, 响应振幅随简谐激励力频率的变化出现"真实"随机共振,随固有频率的变化出现抑制和 共振两种现象.     

调幅波的单模激光线性模型随机共振

对单模激光增益模型的光强方程加入调幅波，用线性化近似方法计算了以δ函数形式关联的两白噪声驱动下光强的输出功率谱及信噪比. 结果表明，信噪比不但随着抽运噪声和量子噪声强度的变化出现随机共振，而且随着高频载波信号频率和低频调制信号频率的变化也出现了随机共振. 关键词： 抽运噪声 单模激光 随机共振 调幅波     

Intensity correlation time of a single-mode laser driven by two coloured noises with coloured cross-correlation with direct signal modulation

In this paper, the intensity correlation time T is studied for the gain-noise model of a single-mode laser driven by coloured pump noise and coloured quantum noise with coloured cross-correlation with a direct signal modulation. By using the linear approximation method, it is found that when the pump noise is modulated directly by a signal, the effects of the cross-correlation between the pump noise and the quantum noise will disappear. In addition, there exists a maximum (i.e. resonance) in the curve of the intensity correlation time $T$ versus the pump noise self-correlation time \tau¹. Furthermore, when \tau¹\le\tau², the intensity correlation time T increases monotonically with the increase of $D$ and decreases monotonically with the increase of Q, but when \tau¹>\tau², the intensity correlation time T increases monotonically with the increase of Q and decreases monotonically with the increase of D.     

Influences of Modulated Noise on Normalized Intensity Fluctuation in a Single-Mode Laser

The influences of the two forms of modulated noises,i.e.the bias signal-modulated noise and the direct signalmodulated noise,on the normalized intensity fluctuation (NIF) are investigated,and the results of the two forms of modulation are compared in detail,We find that a minimum for the case of the bias signal modulation appears in the curve of the dependence of the NIF upon the quantum and pump noise intensities when the correlation coefficient between the quantum noise and the pump noise is negative.However,the NIF for the case of the direct signal modulation is independent of the correlation coefficient between the two noises.Moreover,at the same parameter region,the NIF for the bias signal modulation is only one-eighth as much as.that for the direct signal modulation.