In Situ Supercontinuum Nanopatterning of Silicon Surface by Femtosecond Laser Superfilaments

We for the first time theoretically predict and experimentally demonstrate that selective, low-threshold excitation and interference between short-wavelength plasmons on silicon surfaces photoexcited by infrared femtosecond laser pulses give rise to appearance of permanent sub-diffraction surface gratings with their periods down to 100 nm, dramatically differing from near-wavelength surface gratings succeeding the common “laser photon-surface polariton” interference. Such selectivity was provided in this work by in situ white-light (supercontinuum) femtosecond source generated in a multi-filamentation regime in a thin water layer atop the silicon surface, supporting high-efficiency excitation and dynamic tracking of the transiently tunable plasmon resonance on silicon surface for its easy, robust and ultimate surface nanopatterning.