Sample interview questions: Describe the principles behind optical pumping and its role in laser physics.
Sample answer:
Optical pumping is a process in which atoms or molecules are excited to a higher energy level through the absorption of light. This process is essential for the operation of lasers, as it creates a population inversion—a condition in which there are more atoms or molecules in the excited state than in the ground state.
The basic principle behind optical pumping is that atoms or molecules have specific energy levels that correspond to their electronic structure. When light is incident on an atom or molecule, it can be absorbed if its energy matches the difference between two energy levels. This absorption process excites the atom or molecule to the higher energy level.
In order to achieve a population inversion, the atoms or molecules must be pumped into the excited state faster than they can decay back to the ground state. This can be accomplished by using a pump laser that is tuned to the specific energy difference between the two levels. The pump laser light is directed at the atoms or molecules, causing them to absorb energy and become excited.
Once a population inversion has been created, the excited atoms or molecules can be stimulated to emit light by a second laser pulse, known as the signal laser. The signal laser is als… Read full answer