强双折射光纤中色散效应对偏振模传输的影响

本文研究了在强双折射光纤中色散效应对偏振模传输的影响.发现当二阶色散系数较大时,偏振模能稳定传输,但所需入纤功率较高;当降低二阶色散影响以降低对光源要求时,三阶色散对偏振模长距离传输起破坏作用,三阶色散参量越大,对偏振模的破坏也越大.     

Strong optical feedback in birefringent dual frequency laser

Strong optical feedback in a birefringent dual frequency He--Ne laser with a high reflectivity feedback mirror has been investigated for the first time. The output characteristics of two orthogonally polarized modes are demonstrated in two different optical feedback cases: one is for both modes being fed back and the other is for only one of the modes being fed back. Strong mode competition can be observed between the two modes with strong optical feedback. And when one mode's intensity is near its maximum, the other mode is nearly extinguished. When both modes are fed back into the laser cavity, the mode competition is stronger than when only one mode is fed back. The difference in initial intensity between the two orthogonally polarized modes plays an important role in the mode competition, which has been experimentally and theoretically demonstrated.     

Intensity modulation in single-mode microchip Nd：YAG lasers with asymmetric external cavity

Intensity modulation induced by the asymmetric external cavity in single-mode microchip Nd:YAG lasers is presented. Two kinds of experimental results are discussed based on multiple feedback effects. In one case, the intensity modulation curve is a normal sine wave, whose fringe frequency is four times higher than that of a conventional optical feedback system, caused by multiple feedback effects. In the other case, the intensity modulation curve is the overlapping of the above quadruple-frequency signal and conventional optical feedback signal, which is determined by the additional phase difference induced by the asymmetric external cavity. The theoretical analyses are in good agreement with the experimental results. The quadruple-frequency modulation of the laser output intensity can greatly increase the resolution of displacement measurement of an optical feedback system.     

以十二烷基麦芽糖为模板合成导电聚苯胺纳米线

以绿色表面活性剂十二烷基麦芽糖为软模板,在不同pH值条件下合成了导电聚苯胺纳米线,研究了不同酸度对所得材料电导率的影响,发现电导率随酸度的增加成上升趋势.这是具有良好生物兼容性十二烷基麦芽糖作为表面活性剂首次用于导电聚合物纳米材料的合成.     

聚乙烯/碳黑导电复合材料的导电性能

提出并验证了聚乙烯/碳黑(PE/CB)导电复合材料的网络导电性能和产生正温度系数(PTC)特性的原因,分析了加工过程、温度和辐射交联等后处理过程对其导电性能的影响.     

基于自由曲面变形方法的离心泵三维叶片反问题方法

针对传统离心泵三维扭曲叶片反问题难以实现,提出了基于自由曲面变形的离心泵三维扭曲叶片反问题方法。将叶片工作面与背面的压力之差作为叶片载荷,依据设计叶片实际载荷与目标载荷间的差值来驱动叶片的变形,依次对叶片前、后盖板流线型线进行变形控制。提出了依据前、后盖板流线型线及叶片进出口边形状对叶片各轴面截线形状进行控制的策略。算例的计算结果表明,通过所提出的反问题方法得到的叶片型线与目标叶型吻合程度较好,在设计工况点及非设计工况点的效率偏差均在0.6%以内,能够较快速、准确地实现离心泵三维扭曲叶片的反问题设计。该研究为离心泵三维扭曲叶片的反问题方法提供了参考。     

A Toy Model for Estimation of the Event Plane Non-Flat Effect on an Elliptic Flow in Heavy Ion Collision

In heavy ion collision, the event plane is a key parameter defined as the plane composted by the impact parameter b and beam axis z, It is a crucial reference for various observables, which focus on the initial spatial anisotropy of the overlap region in heavy ion collision. We notice that in some recent heavy ion collision experiments, due to potentially inefficient or even the invalidity of experimental facilities, the reconstructed event plane, which is used in elliptic flow study, may be biased towards a non-flat distribution. In this study, we develop a toy model for fast estimation of the bias effect and its influence on the elliptic flow. The possible azimuthal bias of the detector is firstly studied by varying the part of its azimuthal information. We also study on the limit acceptance of the detector, which will be used to measure the particle of interest in an elliptic flow. The outcomes are presented by comparing the flow study results with or without the non-flat effect on the event plane.     

基于扭转模腔的全固态单纵模拉曼黄光激光器设计

输出波长在560~590nm的全固态拉曼黄光激光器是近几年兴起的激光器之一。目前,此类激光器内部多模振荡引起的黄光输出谱线单色性较差的问题还没有得到解决。针对这一情况,提出将扭转模腔与拉曼复合腔相结合的新型解决方案,从根本上消除增益介质中空间烧孔效应引起的基频光多模振荡,实现单纵模黄光输出。拉曼复合腔由L型基频光谐振腔与直线型拉曼谐振腔耦合而成,既保证各个非线性变换过程可充分利用腔内的高功率密度,又可相对独立地对不同波长的光路进行优化调节,从而使整个系统实现最佳输出。该设计有助于在全固态拉曼激光器中实现毫瓦量级的单纵模黄光输出,为基于黄激光的生物医疗、钠导星、空间目标识别等系统提供理想的固体黄光光源。     

HeNe双频激光器频差的激光内雕赋值法

在精密测量领域,HeNe激光器是制造激光干涉仪的首选.但能够产生中频差4—40 MHz的双折射-塞曼双频HeNe激光器的频差是随机的,小到几百kHz,大到十几MHz.为了让频差能够满足制作双频激光干涉仪的要求,曾出现过弹性加力法、钻孔应力调节法等调整和频差赋值的方法.但这些方法在实际应用中都不是很理想.采用激光内雕法赋值频差,通过在激光器的平面输出镜内部雕刻出不同图案,使平面镜内部产生满足要求的相位延迟,达到为频差赋值的目的.激光内雕法有很多优点:不损害激光器,美观;功率损失小,出光强度可接近原始光强度;可反复赋值,频差在0—60 MHz范围内可调整;频差的稳定性好,采用稳频措施后频差的波动范围小于每小时10 kHz.