The double-edged sword of femtosecond laser-induced periodic surface structures for sub-diffraction and high-efficient nanotexturing

Laser-induced periodic surface structures (LIPSS) have gained lots of attention for the rich physics and potentials in subdiffraction nanostructuring. Herein, we report new aspects of LIPSS to uniformly extend the periodicity to macro, or conversely suppress the periodicity to obtain freeform nanostructures. We have focused on the electron excitation, effective surface permittivity modifications, and plasmonic standing wave ablation for the structure origination and evolution. A plasmonic nanoimprinting model in long range and a nanohole-based light field enhancement in the nearfield are proposed, which are in good accord with the experiments. The nanotextured surface is obtained in a large area by light tailoring method with a cylindrical lens focusing and scanning. Besides, a critical power control method to confine the light field in nanoregion are conducted to obtain the freeform nanostructures, which have potential applications in birefringent optics and nanoscience.