Entropy and equilibrium property of QCD-instanton induced final state in deep-inelastic scattering

The scaling and additivity properties of Rényi entropy in rapidity space of the instanton final state (IFS) and current jet identified by the r-sorting method from the QCDINS Monte Carlo event sample are to saturation with decreasing phase space scale. Furthermore, it is found that the additivity of H2 holds well for the IFS in narrow rapidity windows at different positions. These results indicate that the IFS produced in the instanton-induced process of deep inelastic scattering has reached local equilibrium.     

存在偏振相关损失条件下偏振模色散的特点

偏振模色散和偏振相关损失的联合作用，会产生不规则的色散现象，这一点不能直接通过琼斯距阵本征分析法的运用进行描述。由此引出了对偏振模色散和偏振相关损失共存条件下的研究。通过对琼斯本征分析法进行修正，来分析存在偏振相关损失条件下偏振模色散的特征距阵，理论分析表明，由于偏振相关损失的影响，即使在忽略差分损耗频率相关性的条件下，偏振模色散的特征距阵也会产生根本性的变化。     

包含高阶色散的色散缓变光纤中交叉相位调制不稳定性分析

从包含高阶色散的广义非线性薛定谔方程出发,得到了色散缓变光纤中交叉相位调制不稳定增益谱,研究了增益谱随入射功率及光纤纵向色散参量的变化关系.结果表明：由于四阶色散的影响,在色散缓变光纤的正、反常色散区,交叉相位调制不稳定均发生在两个频谱区.反常色散区两频谱区宽度均比正常色散区宽,且反常色散区第二频谱区更靠近零点,说明色散缓变光纤中交叉相位调制不稳定更容易发生在反常色散区.增益谱宽都随两入射光波功率比值的增加而增大.色散缓变光纤中交叉相位调制不稳定增益谱宽比常规光纤的宽,且随着光纤纵向色散参量μ的增大色散缓变光纤中交叉相位调制不稳定越来越明显.     

DSB optical mm-wave with signal only on optical carrier generated by embedded LiNbO3 Mach-Zehnder modulator

We have investigated the generation of the 40-GHz double-sideband optical millimeter (mm)-wave with signal carried only by its optical carrier via an embedded LiNbO₃ Mach-Zehnder modulator (LN-MZM). Since the optical carrier and its two first-order sidebands are dominant and their powers are well balanced, the first-order harmonic in the photocurrent gets maximal. As the optical mm-wave signal is transmitted along the fiber, there is no code outline distortion because the signal is only modulated on the optical carrier. Although the first-order harmonic shows the periodical fading effect when the optical mm-wave signal is transmitted along the fiber, its degradation on the radio-over-fiber link can be avoided by adjusting the position of the fading nodes via varying the main MZM bias voltage, and the signal still keeps much good eye diagram even after 50-km fiber transmission. The experimental results prove our theory.     

A tunable and reconfigurable microwave photonic filter based on two cascaded modulators and a dispersive medium

A novel tunable and reconfigurable microwave photonic filter based on two cascaded modulators and a dispersive medium is proposed, theoretically discussed and experimentally demonstrated. A single-wavelength LD and a modulator (either a Mach-Zehnder modulator or a phase modulator which can avoid the dc bias drift problem) are used to obtain a multi-wavelength optical source. By adjusting the modulation frequency and the bias voltage on the modulators, the wavelength spacing and the relative amplitude of the optical tones change, thus making the filter tunable and reconfigurable. The experimental results show that the proposed filters have good tunability and reconfigurability and the mainlobe-to-sidelobe ratio of around 25 dB is achieved.     

基于菲涅耳透镜阵列的红外气体传感器

菲涅耳透镜同时具有分光与会聚特性, 且体积小、重量轻和易复制, 使其在光谱检测中得到逐步应用, 但典型光谱成像仪采用菲涅耳透镜沿光轴扫描的方法来获得连续谱线, 不利于光谱仪的稳定性。考虑到气体探测需求, 选用多通道方式来获得多光谱, 提出了一种基于菲涅耳透镜阵列的新型红外气体传感器, 可实现吸收波长在3～5 μm的CO2,CO,CH4,SO2气体的实时检测。利用球面波的传输理论和瑞利判据, 推导了菲涅耳透镜光谱分辨率与透镜结构参数之间的函数关系, 并以光谱分辨率小于50nm为性能指标, 对1μm工艺的8台阶菲涅耳透镜阵列的结构参数进行了计算和误差分析。结果表明, 透镜阵列所需焦距为47.84 mm, 平均数值孔径大于0.4。     

液晶光阀的电光色散特性研究

分析液晶光阀(LCLV)的电光色散特性,重点研究扭曲向列型液晶光阀TB3639的电光色散特性。在温度为27 ℃时, 将TB3639液晶光阀置于频率为1 000 Hz的交流电场中,测出电光特性T-λ曲线,同时得到不同波长的T-V电光特性曲线,确定对比度与光波波长的函数关系k(λ),并得出电光色散特性关系曲线k(λ)～λ。分析结果表明, TB3639液晶光阀在可见光区域,具有相对较高的对比度,其色散较小。波长在450～750 nm区域其对比度均大于0.8;其中波长在550～670 nm区域其对比度变化不大,均大于0.95,其色散最小。     

10 Gb/s光纤通信系统一阶偏振模色散动态补偿系统反馈控制的实现

在偏振模色散(PMD)自动补偿技术中,如何根据反馈信号得到相应的控制信号,使补偿速度跟随偏振模色散变化始终是该技术的一个核心问题。提出了一种新颖的自适应抖动跟踪算法,完成了以微波信号为反馈的多自由度的一阶偏振模色散自动反馈补偿系统的跟踪补偿实验。算法成功地解决了传统算法在跟踪搜索过程中易陷入局部极值的问题,有效地克服了系统中的重要控制器件偏振控制器的磁滞现象以及动态补偿时跟踪搜索过程中易出现的瞬间恶化现象。实验结果表明该算法在对出现突发偏振模色散扰动后自动进行补偿的响应速度在ms量级,最快能达到1~2 ms。     

Widely tunable dual-pump parametric amplifiers with photonic crystal fibres

This paper theoretically studies the double-pumped fibre-optical parametric amplifiers （FOPAs） in photonic crystal fibres. Two distinct working regimes of FOPAs are researched, which depend on the dispersion at the central wavelength of the two pumps. Extremely broad tuning range can be obtained when the central pump wavelength is in the normal dispersion regime and is insensitive to the wavelength separation between the two pumps, while the tuning range is narrow in the anomalous dispersion regime and can be significantly enhanced by increasing the wavelength separation. Impacts of higher-order dispersions and temporal walk-off on the gain spectra are also discussed.     

Higher-order effects on self-similar parabolic pulse in the microstructured fibre amplifier

By considering higher-order effects, the properties of self-similar parabolic pulses propagating in the microstructured fibre amplifier with a normal group-velocity dispersion have been investigated. The numerical results indicate that the higher-order effects can badly distort self-similar parabolic pulse shape and optical spectrum, and at the same time the peak shift and oscillation appear, while the pulse still reveals highly linear chirp but grows into asymmetry. The influence of different higher-order effects on self-similar parabolic pulse propagation has been analysed. It shows that the self-steepening plays a more important role. We can manipulate the geometrical parameters of the microstructured fibre amplifier to gain a suitable dispersion and nonlinearity coefficient which will keep high-quality self-similar parabolic pulse propagation. These results are significant for the further study of self-similar parabolic pulse propagation.