  The effects of ultra-short laser pulses on reactive Ti/Al nano-layered thin
film were investigated. The thin film composed of alternated titanium and
aluminium nano-layers, was deposited by ion-sputtering. Single pulse
irradiation was conducted in the air with focused and linearly polarized
femtosecond laser beam - of 1026 nm wavelength and pulse duration of 170 fs.
Laser induced composition and morphological changes, using different microscopy
techniques and energy dispersive X-ray spectroscopy, were investigated.
Following results were obtained: (i) one step partial/selective ablation of
upper Ti layer from nano-layer Ti/Al at low laser fluence and (ii) two step
ablation or entire ablation of nano-layer Ti/Al at higher laser fluence. Single
pulse selective ablation of the upper Ti layer was confirmed based on profiling
(AFM) along the ablation steps and reduction of Ti concentration (EDX) in the
ablated areas. Ablation threshold was estimated using well known procedure for
ultra-short laser pulses - spot diameter square versus logarithm of pulse
energy. To interpret the experimental observations, simulations have been
performed to explore the thermal response of the multiple layered structure
(Ti(5x(Al/Ti))) after irradiation with a characteristic value of single laser
pulse of fluence F = 320 mJ/cm2. The results are in agreement with the
calculations.
