Femtosecond time resolved studies of laser ablation

Laser ablation has proven to be an important technology in an increasing number of applications. The fundamental mechanisms underlying laser ablation processes are quite complicated, and include laser interactions with the target as well as plasma development off the target. While substantial progress has been achieved in understanding laser ablation on the nanosecond and picosecond time scales, it remains a considerable challenge to elucidate the underlying mechanisms during femtosecond laser ablation. We present experimental observations of plasma development inside silica glass during single femtosecond laser pulse (100 fs, 800 nm) irradiation. Using a femtosecond time-resolved imaging technique, we measured the evolution of a laser-induced plasma inside the glass that has an electron number density on the order of 10¹⁹ cm^-3. Additionally, we observed an air plasma outside the target which forms long before the explosion of a material vapor plume.