The carrier-envelope phase (CEP) φ0 is one of the key parameters in the generation of isolated attosecond pulses. In particular, “cosine” pulses (φ0 = 0) are best suited for generation of single attosecond pulses in atomic media. Such “cosine” pulses have the peak of the most intense cycle aligned with the peak of the pulse envelope, and therefore have the highest contrast between the peak intensity and the neighboring cycles. In this paper, the dynamics of single attosecond pulse generation from a relativistically oscillating plasma mirror is investigated. We use an elementary analytical model as well as particle-in-cell simulations to study few-cycle attosecond pulses. We find that the phase of the field driving the surface oscillations depends on the plasma density and preplasma scale length. This leads us to a counterintuitive conclusion: for the case of normal incidence and a sharp plasma–vacuum boundary, the CEP required for the generation of a single attosecond pulse phase is closer to φ0 = π/2 (a “sine” pulse), with the exact value depending on the plasma parameters.

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相对论振荡镜产生阿秒脉冲中密度相关的载波包络相移

载波包络相位 (CEP) φ0 是生成隔离阿秒脉冲的关键参数之一。特别是，“余弦”脉冲（φ0 = 0）最适合在原子介质中生成单个阿秒脉冲。这种“余弦”脉冲的最强周期的峰值与脉冲包络的峰值对齐，因此峰值强度与相邻周期之间的对比度最高。在本文中，研究了相对论振荡等离子体镜产生单阿秒脉冲的动力学。我们使用基本分析模型以及细胞内粒子模拟来研究少周期阿秒脉冲。我们发现驱动表面振荡的场的相位取决于等离子体密度和前等离子体尺度长度。这使我们得出一个违反直觉的结论：