Picosecond ablation dynamics of transparent materials studied by oscillating reflectivity

Kumada, Takayuki   ; Akagi, Hiroshi; Itakura, Ryuji; Otobe, Tomohito; Yokoyama, Atsushi

We found about 70 ps-period of oscillation in time-resolved pump-probe reflectivity of fused silica irradiated with ultrafast laser pulse (800 nm, 50 fs, 10 J/cm). We suggest that the oscillation results from interference of reflection beams from front and rear surfaces of electrically excited plasma area, which melts and adiabatically expands by decomposing into liquid and vapor phase. The velocity of the expansion is estimated to be about 10 m/s.