Chapter 4: Laser Induced Plasma: Fundamentals and Characterization

Laser-induced plasma (LIP) can be distinguished from other plasmas such as discharge plasma, inductively coupled plasma (ICP), etc. due to its violent expansion into the ambient atmosphere. LIPs are generated as a result of radiation absorption by the target material in solid, liquid, gaseous, or aerosol state, of a high-power laser pulse. The physical and chemical characteristics of the LIP depend on the experimental and ambient conditions, including the laser parameters (spot size, pulse width, wavelength, irradiance, etc.), the nature and state of the target material, and the surrounding environment. LIP is generally analysed by optical emission spectroscopy using high-resolution spectroscopy systems. A typical LIP emission spectrum includes a large number of closely spaced emission lines carrying vital information about the target material. LIPs, as a spectroscopic source experience a fast temporal evolution of their characteristic parameters, from ablation of material to the formation of plasma during absorption of the laser pulse. Apart from the spectroscopic techniques, diverse electrical devices are also used to study the kinetics of LIPs, such as the localized space potential, electron temperature, and density. LIPs have been used for various technological applications in several fields, such as defence, forensics, space exploration, public health, the environment, and more.