Arbitrary control of the electromagnetic field in femto-nano scale has attracted significant research attention in nano-photonics. Although the electromagnetic field controlled in femto-nano scale could be realized by illuminating metallic nanoparticles with femtosecond chirped laser pulses, the quantitative relation of the laser chirp and the temporal evolution of the plasmonic field hasn’t yet been fully revealed. Here, active control of the localized plasmonic field is demonstrated by a chirped femtosecond laser pulse in an asymmetric Au nano-cross system within nm-fs scale using the finite differential time domain method. The transferring of the plasmonic field between the two poles of the nanocross is determined by the laser chirp and exhibits linear dependence on the time interval between the corresponding plasmonic resonant frequencies dispersed in the chirped laser pulse. The arrival time and amplitude of the peak field from the plasmonic hot spot are determined by the superposition of the induced field excited by the on-resonant and off-resonant frequency components distributed in the chirped laser pulse. The peak field would arrive behind the resonant frequency component for sufficient oscillation of the localized field. This relative delay between the resonant frequency and field peak is influenced by the temporal distribution of the resonant frequency in the chirped pulse and the response of localized field interpreted by the damped harmonic oscillator model. This result demonstrates that larger near-field enhancement is determined by not only the temporal sequence of the frequency component modulated by chirp but also the temporal distribution of the resonant frequency.

中文翻译：

---

通过啁啾飞秒激光脉冲控制纳米飞秒尺度的等离子体场的动力学

飞纳米尺度电磁场的任意控制引起了纳米光子学的重大研究关注。尽管可以通过用飞秒啁啾激光脉冲照射金属纳米粒子来实现飞纳米尺度控制的电磁场，但激光啁啾与等离子体场的时间演变的定量关系尚未完全揭示。在这里，局部等离子体场的主动控制通过使用有限微分时域方法在 nm-fs 尺度内的非对称 Au 纳米交叉系统中的啁啾飞秒激光脉冲来证明。纳米交叉的两个极点之间的等离子体场的转移由激光啁啾决定，并且表现出对分散在啁啾激光脉冲中的相应等离子体共振频率之间的时间间隔的线性依赖性。来自等离子体热点的峰值场的到达时间和幅度是由分布在啁啾激光脉冲中的谐振和非谐振频率分量激发的感应场的叠加决定的。对于局部场的充分振荡，峰值场将在谐振频率分量之后到达。谐振频率和场峰值之间的这种相对延迟受到啁啾脉冲中谐振频率的时间分布和阻尼谐振子模型解释的局部场响应的影响。该结果表明，更大的近场增强不仅由线性调频调制的频率分量的时间序列决定，还取决于谐振频率的时间分布。