Abstract Coherent control is an ingenious tactic to steer a system to a desired optimal state by tailoring the phase of an incident ultrashort laser pulse. A relevant process is the two-photon–induced photoluminescence (TPPL) of nanoantennas, as it constitutes a convenient route to map plasmonic fields, and has important applications in biological imaging and sensing. Unfortunately, coherent control of metallic nanoantennas is impeded by their ultrafast femtosecond dephasing times so far limiting control to polarization and spectral optimization. Here, we report that phase control of the TPPL in resonant gold nanoantennas is possible. We show that, by compressing pulses shorter than the localized surface plasmon dephasing time (<20 fs), a very fast coherent regime develops, in which the two-photon excitation is sensitive to the phase of the electric field and can therefore be controlled. Instead, any phase control is gone when using longer pulses. Finally, we demonstrate pure phase control by resorting to a highly sensitive closed-loop strategy, which exploits the phase differences in the ultrafast coherent response of different nanoantennas, to selectively excite a chosen antenna. These results underline the direct and intimate relation between TPPL and coherence in gold nanoantennas, which makes them interesting systems for nanoscale nonlinear coherent control.

中文翻译：

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在超快相干区通过纯光谱相位控制选择性激发单个纳米天线

摘要 相干控制是一种巧妙的策略，通过调整入射超短激光脉冲的相位，将系统引导到所需的最佳状态。一个相关的过程是纳米天线的双光子诱导光致发光 (TPPL)，因为它构成了绘制等离子体场的便捷途径，并且在生物成像和传感中具有重要应用。不幸的是，金属纳米天线的相干控制受到其超快飞秒移相时间的阻碍，迄今为止限制了对极化和光谱优化的控制。在这里，我们报告了共振金纳米天线中 TPPL 的相位控制是可能的。我们表明，通过压缩比局部表面等离子体去相时间（<20 fs）短的脉冲，会形成非常快的相干机制，其中双光子激发对电场的相位敏感，因此可以控制。相反，当使用更长的脉冲时，任何相位控制都消失了。最后，我们通过采用高度敏感的闭环策略来证明纯相位控制，该策略利用不同纳米天线的超快相干响应中的相位差，选择性地激发选定的天线。这些结果强调了金纳米天线中 TPPL 与相干性之间的直接和密切关系，这使得它们成为纳米级非线性相干控制的有趣系统。它利用不同纳米天线的超快相干响应中的相位差，选择性地激发选定的天线。这些结果强调了金纳米天线中 TPPL 与相干性之间的直接和密切关系，这使得它们成为纳米级非线性相干控制的有趣系统。它利用不同纳米天线的超快相干响应中的相位差，选择性地激发选定的天线。这些结果强调了金纳米天线中 TPPL 与相干性之间的直接和密切关系，这使得它们成为纳米级非线性相干控制的有趣系统。