排序方式: 共有26条查询结果,搜索用时 171 毫秒
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.
4.
5.
6.
Broadband continuum generation in an irregularly multicore microstructured optical fiber 总被引:1,自引:0,他引:1
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.
A study of ultrafast electron diffusion kinetics in ultrashort-pulse laser ablation of metals 总被引:1,自引:0,他引:1 下载免费PDF全文
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.
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