用反射式纯相位液晶空间光调制器产生涡旋光束

利用反射式纯相位型液晶空间光调制器(LCSLM)实时动态地产生不同拓扑荷数的涡旋光束,能量转换效率高达60%。并分析了其与平面波以及球面波的干涉特性。当CCD在非成像面上时,涡旋中心出现暗核,且其直径随拓扑荷数的增加而增大。实验结果和理论分析基本一致。     

光学薄膜弱吸收测试装置参数优化

光学薄膜对入射光的弱吸收特性是评价元件质量的重要参数.在高能激光作用下,即使十分微弱的吸收也将足以导致薄膜元件的灾难性破坏.因此,有必要对光学薄膜的平均吸收及局部吸收进行精确、快速、实时的检测.从光热偏转技术发展而来的表面热透镜法由于其对测试装置要求的放宽,并且同样拥有较高的测试精度,是测试元件薄膜弱吸收特性的有效方法...     

二维正方光子晶体波导中的慢光传输

采用平面波展开法分析了正方晶格光子晶体线缺陷波导中的慢光传输.数值模拟结果表明,介质柱光子晶体线缺陷波导中,缺陷模的群速度与填充比、缺陷处介质柱半径及与波导相邻介质柱半径有关,其中缺陷处介质柱半径对缺陷模的群速度影响最大|随着填充比和缺陷处介质柱半径的增大及与波导相邻介质柱半径的减小,缺陷模的群速度逐渐减小且最小减至0.015c.进而对比研究空气柱光子晶体线缺陷波导,发现缺陷模的群速度随着缺陷处空气柱半径的减小而减小,最小减至0.008c.     

INVESTIGATION OF PHOTOREFRACTIVE TWO-WAVE COUPLING IN Cr-DOPED STRONTIUM BARIUM NIOBATE CRYSTAL

We present here the experimental results of photorefractive two-wave coupling in the congruent strontium barium niobate (SBN:61) crystal doped with 1000ppm Cr. Employing a He－Ne laser (632.8nm), we observed the coupling characteristics under different conditions. The crystal shows excellent photorefractive properties, with a high coupling coefficient nearly 6cm^-1 as the beam intensity ratio m is less than 100. The saturated coupling coefficient of SBN:61:Cr shows a maximum at a certain external beam crossing angle 2θ_peak, which varies with different m, showing a nearly linear dependence on m. The saturated coupling response time τ is measured to be less than 0.8 s. The response time decreased with increasing beam crossing angles no matter how large m is. We also observed the behaviour of the probe beam in reversed experimental procedures. We found that the probe beam shows a bistable state in both procedures.     

Light-induced scattering in SBN：Cr crystal under external electric fields and its suppression

In this paper, the enhancement of light-induced scattering in congruent SBN:Cr (Sr_{0.61}Ba_{0.39}Nb_2O_6:Cr) crystals in the presence of an externally applied electric field and its suppression are studied. If a coherent image is focalized in SBN:Cr crystal without applying external electric field, the output image will remain clear, because of the weak photorefractive effect in the crystal. When a field is applied properly along the crystal axis, markedly enhanced scattering from the signal beam and the output image dispersion can be observed due to the increase of the photorefractive two-beam coupling gain and the light-induced index change in SBN:Cr crystals. By introducing a coherent or incoherent beam with higher intensity the light-induced scattering can be suppressed through the erasure of scattering gratings. The difference between coherent and incoherent beam is that the former can also amplify the signal beam as the scattered light is removed, whereas the latter can only make the signal beam revert to its initial state. The results obtained under different experimental conditions are consistent with theoretical analysis.     

基于半球空间光纤阵列的双向反射分布测量

提出了一种基于半球空间光纤阵列的双向反射分布函数(BRDF)测量方法与系统.将多根光纤组成的阵列均匀分布于一半球面上,使球心处物体表面反射的光在三维空间中的角分布转换为同一平面上的二维图像,经CCD采集及相应的数据处理,可实现对物体表面双向反射分布函数的快速测量.同时,利用光纤将照射激光束传输到物体表面待测点,并通过光纤的弯曲角度可改变光束的入射角.利用该测量系统对不同材质、不同加工工艺的物体表面的激光反射分布进行了初步的测量和分析.结果表明,相比传统的扫描式测量系统,该测量系统在提高测量速度的同时,避免了由于光源功率的起伏和探测器响应度的涨落所引起的测量误差,且结构简单,使用方便.     

光诱导准一维光子晶格中离散空间光孤子的相互作用

基于分步束传播法数值分析了离散空间光孤子在准一维光诱 导光子晶格中的相干与非相干相互作用过程. 结果表明: 对于相干孤子, 同相时相互吸引, 反相时相互排斥. 然而, 由于非线性响应的各向异性, 横向排布的非相干孤子会因间隔波导数目的增加而由相互吸引变为相互排斥. 并且, 沿对角方向排布的两个非相干孤子在孤子相 互作用力和布拉格反射的共同影响下, 会呈现出"钟摆式"振荡传输现象. 研究结果有助于进一步理解非线性各向异性对离散孤子相互作用的影响机制, 并为后续实验研究提供理论参考.     

磁致伸缩材料弱磁场响应特性的实验研究

针对磁致伸缩材料在弱磁场传感器领域的应用需要,采用迈克耳逊干涉原理实验测量了零应力条件下Tb-Dy-Fe材料和Fe-Ga合金的磁场响应灵敏度,以及不同应力下Fe-Ga合金的磁场响应特性和温度响应特性.实验结果表明：在零应力,外加磁场16 mT条件下,Fe-Ga合金的磁场响应灵敏度远高于Tb-Dy-Fe材料,更合适作为弱磁场传感器敏感材料;同时,在1.2 MPa预应力和26 mT偏置磁场下,Fe-Ga合金材料具有较好的磁场响应灵敏度和较大的饱和磁致伸缩系数,因而处在最佳工作状态.所得到的材料的磁场和温度响应曲线可作为弱磁场传感器参量设计的参考依据.     

The interaction of in-band and in-gap lattice soliton trains in optically induced two-dimensional photonic lattices

We demonstrate the coherent interactions of lattice soliton trains,including in-band solitons (IBSs) and gap soliton trains (GSTs),in optically induced two-dimensional photonic lattices with self-defocusing nonlinearity.It is revealed that the π-staggered phase structures of the lattice soliton trains will lead to anomalous interactions.Solely by changing their initial separations,the transition between attractive and repulsive interaction forces or reversion of the energy transfer can be obtained.The 'negative refraction' effect of the soliton trains on the interaction is also discussed.Moreover,two interacting IBSs can merge into one GST when attraction or energy transfer happens.     

压电陶瓷驱动的动态匹配光栅滤波解调法优化

提出并实验验证了一种动态匹配光栅滤波系统的优化解调方法.在压电陶瓷驱动的动态匹配(光纤)光栅滤波解调系统中,一方面采用上升高压锯齿波,以消除压电陶瓷滞回效应;另一方面将压电陶瓷电压与伸长量关系的反函数作为锯齿波上升电压,以校正压电陶瓷的非线性;进而,为实现解调系统的温度补偿,引入一根中心波长保持不变的参考(光纤)光栅.在锯齿波上升过程中,匹配光栅与参考光栅和传感(光纤)光栅在不同时刻匹配,匹配时间差仅与传感光栅有关,而与解调系统温度无关.实验结果表明,优化后系统的线性度可提高2%,灵敏度与理论值的相对误差小于0.6%;在10～60℃范围内,该解调系统温度变化引起的相对误差小于1%.