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Tracing the phase of focused broadband laser pulses
Nature Physics ( IF 19.6 ) Pub Date : 2017-07-10 , DOI: 10.1038/nphys4185
Dominik Hoff , Michael Krüger , Lothar Maisenbacher , A. M. Sayler , Gerhard G. Paulus , Peter Hommelhoff

Precise knowledge of the behaviour of the phase of light in a focused beam is fundamental to understanding and controlling laser-driven processes. More than a hundred years ago, an axial phase anomaly for focused monochromatic light beams was discovered and is now commonly known as the Gouy phase1,2,3,4. Recent theoretical work has brought into question the validity of applying this monochromatic phase formulation to the broadband pulses becoming ubiquitous today5,6. Based on electron backscattering at sharp nanometre-scale metal tips, a method is available to measure light fields with sub-wavelength spatial resolution and sub-optical-cycle time resolution7,8,9. Here we report such a direct, three-dimensional measurement of the spatial dependence of the optical phase of a focused, 4-fs, near-infrared pulsed laser beam. The observed optical phase deviates substantially from the monochromatic Gouy phase—exhibiting a much more complex spatial dependence, both along the propagation axis and in the radial direction. In our measurements, these significant deviations are the rule and not the exception for focused, broadband laser pulses. Therefore, we expect wide ramifications for all broadband laser–matter interactions, such as in high-harmonic and attosecond pulse generation, femtochemistry10, ophthalmological optical coherence tomography11,12 and light-wave electronics13.



中文翻译:

跟踪聚焦宽带激光脉冲的相位

准确了解聚焦光束中光的相位行为是理解和控制激光驱动过程的基础。一百多年前,人们发现了聚焦单色光束的轴向相位异常,现在通常被称为Gouy相位1,2,3,4。最近的理论工作使人们质疑将这种单色相位公式应用到今天无处不在的宽带脉冲上的有效性[ 5,6]。基于尖锐的纳米金属尖端的电子反向散射,可以使用一种方法来测量具有亚波长空间分辨率和亚光学周期时间分辨率的光场7,8,9。在这里,我们报告了这样一种直接的三维测量,它测量了聚焦的4-fs近红外脉冲激光束的光学相位与空间的关系。观察到的光学相位基本上偏离单色Gouy相位-沿传播轴和径向方向都表现出更为复杂的空间依赖性。在我们的测量中,这些明显的偏差是规则的,而不是聚焦宽带激光脉冲的例外。因此,我们希望所有宽带激光与物质的相互作用都将产生广泛的影响,例如在高谐波和阿秒脉冲产生,飞化学10,眼科光学相干断层扫描11,12和光波电子学13中

更新日期:2017-10-11
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