【摘 要】
：
The role of chirp on the light–matter interaction of femto- and pico-second laser pulses with functional structured surfaces is studied using drag-reducing riblets as an example. The three-dimensional, periodic microstructure naturally gives rise to a mut
【机 构】
：
SchoolofPhysics,OsnabrückUniversity,Barbarastr.7,49076Osnabrück,Germany
【出 处】
：
PhotonicsResearch
论文部分内容阅读
The role of chirp on the light–matter interaction of femto- and pico-second laser pulses with functional structured surfaces is studied using drag-reducing riblets as an example. The three-dimensional, periodic microstructure naturally gives rise to a mutual interplay of (i) reflection, (ii) scattering, and (iii) diffraction phenomena of incident coherent light. Furthermore, for femtosecond pulses, the structure induces (iv) an optical delay equivalent to a consecutive temporal delay of 230 fs in places of the pulse. These features enable studying experimentally and numerically the effect of tuning both pulse duration τ and spectral bandwidth Δω on the features of the wide-angle scattering pattern from the riblet structure. As a result, we discovered a significant breakdown of fringes in the scattering pattern with decreasing pulse duration and/or increasing spectral bandwidth. This unique type of chirp control is straightforwardly explained and verified by numerical modeling considering the spectral and temporal interaction between different segments within the scattered, linearly chirped pulse and the particular geometric features of the riblet structure. The visibility of the fringe pattern can be precisely adjusted, and the off-state is achieved using τ
其他文献
介绍光二极管线阵组成的简单光学多道分析系统的原理和性能,及其在激光与光学显示上的应用。
Absolute instability modes due to secondary scattering of stimulated Raman scattering (SRS) in a large nonuniform plasma are studied theoretically and numerically. The backscattered light of convective SRS can be considered as a pump light with a finite b
非固定相机数字散斑相关方法拍摄待测物体表面的目标图像时,所拍摄的目标散斑图像相对于参考散斑图像可能产生位置移动及图像旋转。通过辅助定位的相机标定方法可以计算出被测物体表面与相机的相对位置,但无法获得散斑图像在平面内的旋转角度。数字散斑相关方法对图像旋转较为敏感,随着旋转角度的增加,目标子窗口与参考子窗口的相关性迅速降低。研究图像旋转角度对数字散斑相关方法计算精度的影响,分析相关性随旋转角度降低的原
针对大视场摄像机标定中高精度大尺寸靶标加工困难，小尺寸靶标标定精度不高的问题，提出了一种二维柔性拼接标定方法。二维柔性拼接靶标由多个小平面标定板(又称为子标定板)组成，每个子标定板平面上分为匹配区和扩展区，其中匹配区由编码点组成，多个子标定板通过编码点进行匹配，虚拟拼接成一个大面积的平面靶标(又称为母标定板)，通过计算可以得到母标定板上的坐标值及其相应的像点，从而可以标定出摄像机的内参数。仿真和实验结果表明，该方法和大面积的靶标标定的精度相当，当大面积标定板上的标志点和子标定板扩展区标志点数相同时，其标定
Narrowband microwave generation with tuneable frequency is demonstrated by illuminating a photoconductive semiconductor switch (PCSS) with a burst-mode fibre laser. The whole system is composed of a high-power linearly polarized burst-mode pulsed fibre la
针对现有视频跟踪算法因目标运动机动性强或非对称刚体目标快速变形等情况导致的目标丢失问题,提出了一种基于相关滤波自适应模型与平均峰值相关能量(APCE)重检机制的视频跟踪算法。自适应模型跟踪算法可根据目标区域的清晰度实时调整模型,有效保证目标跟踪模型的准确性。实验结果表明,将自适应模型跟踪算法融入判别式尺度空间跟踪(DSST)模型中,可增强模型对机动性强或快速变形物体的跟踪效果,在保证跟踪速度的同时
当前，激光美容外科的两个有意义的方面是治疗鲜红斑痣和纹身（包括碎片纹身)。 氩激光治疗鲜红斑痣通常是在门诊进行。对7岁以上的儿童，激光疗效经证明后，可在氯胺酮麻醉下进行广泛治疗。应用现有的装置，只能进行小面积治疗，会有点状色素沉着斑出现。激光装置必须改进的能进行大面积治疗，并能防止点状色素沉着。目前的研究还包括用于对照的非相干红外凝固器。一种适合皮肤病的氩激光器目前已可供使用。
采用自由室温活塞取代惯性管及气库作为脉管制冷机(Pulse Tube Cryocooler, PTC)调相机构，不仅可以减小调相机构的体积，还可以提高其制冷性能。为了研究自由室温活塞对脉管制冷机性能的影响，设计加工了一台自由室温活塞脉管制冷机，并进行了实验研究。结果表明，在输入功不变的情况下，运行频率增大时，压缩活塞和自由室温活塞的位移相位角增大，压缩活塞与自由室温活塞的扫气容积之比增大；充气压力增加时，位移相位角增大，扫气容积比减小。研究结果对自由活塞型脉管制冷机的设计及优化具有重要指导意义。