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1.
本文论述光波场的时问、空间对称性,包括拍频导致的“空间放大”与“时间放大”;多束光干涉提高条纹细锐度“空间压缩”、锁模技术中脉冲的“时间压缩”;空间调制与时间调制;非线性效应中的时间倍频与空间倍频;空间相干性与时间相干性;时域测不准与空域测不准。  相似文献   
2.
Long-period fibre gratings inside standard single-mode optical communication fibres are successfully fabricated with infrared femtosecond laser pulses. The refractive index perturbations are well confined within the fibre core by choosing the proper laser focusing parameters and translation speed of the fibre during the direct laser writing process. With the self-focusing effect considered and at a constant average irradiation dose of 1.62 × 10^3 J/(cm^2μm), the threshold intensity for fabricating long-period gratings with infrared femtosecond laser pulses is determined to be 5.13 × 10^13 W/cm2.  相似文献   
3.
贾亚青  朱晓农 《物理学报》2004,53(9):3065-3070
研究了由理想线偏振片和单轴双折射晶体波片组成的双折射滤光片倾斜放置时的二阶色散和 三阶色散特性,包括波片厚度、光线入射角和光轴旋转角的变化对二阶和三阶色散的影响. 还给出了双折射滤光片的群延迟表达式,并就色散特性与GT干涉仪进行了详细比较. 关键词: 双折射滤光片 群延迟 二阶色散 三阶色散  相似文献   
4.
报道在脉宽50fs—22ps,波长800nm脉冲激光作用下的空气电离阈值的研究结果.利用探测等离子体发光信号的方法,实验测量了激发空气电离所需的阈值激光强度.结果表明,当激光脉冲宽度从50fs增加到22ps时,阈值光强Ith从8.7×1014W/cm2下降到2.7×1013W/cm2Ith经历了由迅速降低逐渐发展为缓慢降低的过程.在50fs—1p  相似文献   
5.
光学相干层析系统噪音分析(Ⅱ)——时域OCT和频域OCT   总被引:2,自引:3,他引:2  
本文作为前文《光学相干层析系统噪音分析(I)》的后续,对时域OCT和频域OCT的噪音和灵敏度进行了详细的分析和计算,证明与时域OCT系统不同,频域OCT系统的信噪比与光源带宽和纵向扫描深度无关,频域OCT系统可以在高速率图像采集的情况下仍然保持探测系统的大动态范围.  相似文献   
6.
A broadband continuum generation is reported in a novel multicore microstructured optical fiber (MOF) where irregular air holes are randomly distributed in cladding. By launching ultrashort light pulses from a Ti:sapphire laser into a 190-mm-long fiber of this type, we have observed a group of continua generated from different cores, each with distinct color. 20-dB bandwidth of the broadest continuum is 1260 nm with an average power of 143 mW. The result confirms that the multicore MOF can be fabricated, with different dispersion profiles tailored for specific supercontinuum (SC) generation towards practical applications.  相似文献   
7.
杨建军  刘伟伟  朱晓农 《中国物理》2007,16(7):2003-2010
Temperature dependence of the electron diffusion in metallic targets, where the electron--electron collision is the dominant process, is investigated with the help of an extended two-temperature model. In sharp contrast to the low electron temperature case, where only the electron---phonon collisions are commonly considered, the electron diffusion process underlying the high electron temperatures evolves dramatically different in both temporal and spatial domains. Calculated results of the ablation yield at different pulse durations are presented for a copper plate impinged by ultrashort laser pulses with energy fluences ranging from 0.1 J/cm2 to 10 J/cm2. The excellent agreement between the simulation results and the experimental data indicates the significant role of electron--electron collisions in material ablations using intense ultrashort laser pulses.  相似文献   
8.
本文从理论和实验上分析了存在拍频噪音时时域光学相干层析系统的噪音特性,给出了拍频噪音的具体估算方法.建立了描述一般时域光学相干层析系统实际噪音的简化模型,并给出了测量和寻找平衡探测光学相干层析系统最佳工作状态的方法.理论计算表明,平衡探测光学相干层析系统的信噪比受限于拍频噪音,理想情况下,最大信噪比可达100 dB左右|同时实验表明,如果实际的系统不能完全消除冗余噪音,其信噪比可能要比理论值小10~20 dB.本文的主要结果将可直接用于时域光学相干层析系统工作状态的测试和诊断当中,对频域光学相干层析系统噪音性能的分析和优化也将有所裨益.  相似文献   
9.
飞秒激光烧蚀金属靶的冲击温度   总被引:1,自引:0,他引:1       下载免费PDF全文
王文亭  张楠  王明伟  何远航  杨建军  朱晓农 《物理学报》2013,62(21):210601-210601
在明确飞秒激光与物质相互作用过程冲击温度概念的基础上, 讨论了飞秒激光烧蚀铝靶和铜靶过程中的冲击温度与其他物理量的关系, 利用飞秒激光烧蚀金属的双温模型提取了冲击温度的绝对值, 基于非傅里叶热传导模型计算了冲击温度的分布. 此项研究结果对飞秒激光安全加工含能材料有借鉴意义. 关键词: 飞秒激光 含能材料 烧蚀 冲击温度  相似文献   
10.
Femtosecond(fs) pulse laser ablation of silicon targets in air and in vacuum is investigated using a timeresolved shadowgraphic method. The observed dynamic process of the fs laser ablation of silicon in air is significantly different from that in vacuum. Similar to the ablation of metallic targets,while the shock wave front and a series of nearly concentric and semicircular stripes,as well as the contact front,are clearly identifiable in the process of ablation under 1×10 5 Pa,these phenomena are no longer observed when the ablation takes place in vacuum. Although the ambient air around the target strongly affects the evolution of the ablation plume,the three rounds of material ejection clearly observed in the shadowgraphs of fs laser ablation in standard air can also be distinguished in the process of ablation in vacuum. It is proven that the three rounds of material ejection are caused by different ablation mechanisms.  相似文献   
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