Effects of optical absorbance with ablation characteristics in femtosecond laser irradiation of carbon reinforced Al ₂ O ₃ composites

The thresholds and depths of ablation of carbon [carbon nanotubes (CNTs) or graphene nanoplatelets (GNPs)] reinforced Al2O3 composites were compared and correlated with those of monolithic Al2O3 using femtosecond pulsed laser irradiation (λ = 1027 nm, τP = 380 fs). These composites were processed using a spark plasma sintering method (Ts = 1500°C, τs = 10 min and P = 40 MPa) through which highly densified (more than 97%) composites were fabricated. The optical absorbance of each composite improved in the wavelength range from ultraviolet to near infrared. Compared with the corresponding values for monolithic Al2O3, the ablation thresholds of CNT/Al2O3 and GNP/Al2O3 were 50 and 75% lower respectively, and their ablation depths were two to three times deeper.