Plasma dynamics in ultra-short laser ablation in electronic materials

The ablation of crystalline silicon and copper by ultra-short laser pulses is studied experimentally. A pump-and-probe experiment is implemented in a collinear arrangement as well as side view configuration, utilizing a time delayed frequency doubled probe beam for in situ reflectance measurements and ultra-fast microscopy observation. For the pump beam fluence ranging from 1.5 to 3.0 J/cm², the reflected images show an evidence of lateral plasma expansion up to 500 ps time scale. A fiber optic technique was also used for long time scale shockwave propagation. Important plasma parameters such as energy deposited in the plasma (E), plasma pressure (P), and plasma temperature (T) are estimated by assuming spherical explosion of the shockwave front.