Broad-range ultrafast all-optical red-shifting of EUV surface plasmons: Proof-of-principle and advanced surface nanotexturing in aluminum

摘要

Using aluminum as an example, ultrafast sub-ablative broad-range (EUV-IR) spectral tuning of surface plasmon resonance in metals by IR femtosecond laser pulses was demonstrated by theoretical modeling of prompt surface optics for strongly photoexcited materials and of their surface plasmon-polariton (SPP) dispersion curves, as well as by experimental multi-shot laser imprinting of surface plasmon-polaritons as large-scale regular surface ripples with minimal sub-diffraction periods down to 200 nm. According to laser-pump self-reflection and charge emission experiments, the key issue in the prompt optical tuning (spectral red-shifting) of EUV surface plasmon resonance in aluminum by the IR laser pulses is related to ultrafast surface charging of its surface via intense electron emission during the laser pump pulse, depleting its surface electron density and simultaneously decreasing its surface/bulk plasma frequencies, at the corresponding negligible surface ablative etching.