Spontaneous scaling down of femtosecond laser-induced apertures towards the 10-nanometer level: the excitation of quasistatic surface plasmons

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Abstract

During ultrafast laser ablation on ZnO, the feature sizes of laser-induced apertures always decrease spontaneously with the pulse increasing and the crater extending, and may eventually approach an astonishing 10-nm scale, an ultradeep-subwavelength laser–solid interaction regime relating new physics in laser-induced damage. Based on the fundamental theories of plasmonics, it is proposed that the spontaneous scaling-down originates in the conversion of physical regimes of plasmonic interaction from the optical regime to the electrostatic regime, which arouses quasistatic SPs with interaction scales far beyond the diffraction limit and results in ultrafast, nonthermal ablation for extraordinary electrostatic field enhancement. Basically, “nanoscale” eliminates electromagnetic retardation effects greatly, brings an instantaneous respond to the incident field, and arouses electrostatic interactions with giant local-field enhancement, which may exert tremendous electrostatic forces on superficial electrons and ions and eventually lead to an “ultrafast” electrostatic nanoexplosion. Thus, the characteristics of simultaneous “nanoscale” and “ultrafast” arise spontaneously in femtosecond laser ablation.

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