This study reports the results of experiments on periodic nanostructure formation on diamond-like carbon (DLC) films induced with 800 nm, 7-femtosecond (fs) laser pulses at low fluence from a Ti:sapphire laser oscillator. It was demonstrated that 7-fs laser pulses with a high power density of 0.8⁻2 TW/cm² at a low fluence of 5⁻12 mJ/cm² can form a periodic nanostructure with a period of 60⁻80 nm on DLC films. The period decreases with increasing fluence of the laser pulses. The experimental results and calculations for a model target show that 7-fs pulses can produce a thinner metal-like layer on the DLC film through a nonlinear optical absorption process compared with that produced with 100-fs pulses, creating a finer nanostructure via plasmonic near-field ablation.
Keywords: diamond-like carbon; femtosecond laser; laser ablation; nanostructure formation; near-field; surface plasmon polaritons.