Abstract
Laser ablation using nanosecond pulsed laser light includes some important transient processes during and after laser irradiation. In this paper, the optical absorption of semiconductors and the energy relaxation of excited electrons and holes are briefly described, followed by rapid phase transformation such as transient melting and vaporization which lead to laser ablation of materials. Initial processes of vaporization of solids due to laser ablation have been investigated by several time-resolved measurements. Here we describe a method of time-resolved soft X-ray absorption spectroscopy measurement to show an example of the initial plume produced by laser ablation of Si. This technique gives us information of the time dependence of ejection of Si atoms and Si ions (Si+˜Si4+), and their time-dependent spatial profiles. In addition to nanosecond pulsed laser ablation, characteristics of femtosecond pulsed laser ablation is also discussed, which has been very important to applications.
