Sample interview questions: Describe the principles behind laser-induced plasma formation and its applications.
Sample answer:
Laser-induced plasma formation is a phenomenon that occurs when a high-intensity laser beam interacts with a target material, causing the generation of a highly ionized and energetic plasma. This process involves several fundamental principles, including optical breakdown, ionization, and the propagation of electromagnetic waves.
The principle behind laser-induced plasma formation lies in the concept of optical breakdown. Optical breakdown occurs when a material is exposed to a laser beam with a sufficiently high intensity. At such high intensities, the electric field of the laser beam becomes strong enough to ionize the atoms or molecules in the material. This ionization process leads to the creation of free electrons and positive ions within the material.
The ionization process can occur through different mechanisms, such as multiphoton ionization, tunnel ionization, or avalanche ionization, depending on the laser parameters and the properties of the target material. Multiphoton ionization involves the simultaneous absorption of multiple photons by an atom or molecule, leading to ionization. Tunnel ionization occurs when the electric field of the laser allows electrons to overcome the potential barrier of the atomic or molecular system. Avalanche ionization, on the other hand, involves the multiplication of ionization events due to the presence of free electrons.
Once the ionization process initiates, the generated free electrons and positive ions interact with the laser field and experience acceleration. This acceleration leads to the emission of secondary electrons and the formation of an electron avalanche, which rapidly increases the number of free electrons in the system. The collective motion of these free electrons gives rise to a highly conductive plasma.
The laser-induced plasma has numerous applications in various fields of research and technology. One of the primary applications is in laser-induced breakdo… Read full answer