The spatially dependent phase distribution of focused few-cycle pulses, i.e., the focal phase, is much more complex than the well-known Gouy phase of monochromatic beams. As the focal phase is imprinted on the carrier-envelope phase (CEP), for accurate modeling and interpretation of CEP-dependent few-cycle laser-matter interactions, both the coupled spatially dependent phase and intensity distributions must be taken into account. In this Letter, we demonstrate the significance of the focal phase effect via comparison of measurements and simulations of CEP-dependent photoelectron spectra. Moreover, we demonstrate the impact of this effect on few-cycle light-matter interactions as a function of their nonlinear intensity dependence to answer the general question: if, when, and how much should one be concerned about the focal phase?

中文翻译：

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观察相位量效应对于少周期光物质相互作用的重要性。

聚焦的几个周期脉冲的空间相关的相位分布（即聚焦相位）要比众所周知的单色光束的古伊相位复杂得多。由于聚焦相被印在载流子-信封相（CEP）上，为了精确建模和解释CEP相关的少数周期激光物质相互作用，必须同时考虑耦合的空间相关相位和强度分布。在这封信中，我们通过比较依赖于CEP的光电子光谱的测量结果和模拟结果来证明聚焦相效应的重要性。此外，我们证明了这种效应对几个周期的光-物质相互作用的影响是其非线性强度依赖性的函数，从而回答了一个普遍的问题：是否应该关注焦点相位，何时以及关注多少？