We investigated nonlinear photoemission from plasmonic films with femtosecond, mid-infrared pulses at 3.1 μm wavelength. Transition between regimes of multi-photon-induced and tunneling emission is demonstrated at an unprecedentedly low intensity of <1 GW/cm2. Thereby, strong-field nanophysics can be accessed at extremely low intensities by exploiting nanoscale plasmonic field confinement, enhancement and ponderomotive wavelength scaling at the same time. Results agree well with quantum mechanical modelling. Our scheme demonstrates an alternative paradigm and regime in strong-field physics.
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机译：我们用波长为3.1μm的飞秒，中红外脉冲研究了等离子体膜的非线性光发射。在<1 GW / cm 2 前所未有的低强度下，证明了多光子诱导和隧穿发射机制之间的过渡。因此，可以通过同时利用纳米级等离子体场的限制，增强和质动力波长定标，以极低的强度获得强场纳米物理学。结果与量子力学建模非常吻合。我们的方案展示了强场物理学中的另一种范式和状态。
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