Question

What is meant by population inversion and optical pumping?

Answer 1

Hint: Increasing the population of atoms or electrons in the higher energy state using light such that the population should be more than the population in the lower energy state is called population inversion and this process is optical pumping. This is a non- equilibrium condition of active medium.

Complete step by step answer:
We are given to define population inversion and optical pumping.A situation which is not at equilibrium must be created by adding energy in the higher energy level such that the higher energy level will have more number of atoms or electrons than the lower energy level.

This is called Population inversion and the process by which population inversion is done using light is called optical pumping.

Additional Information:
Normally atoms return to the ground state by releasing the absorbed energy. Therefore, the population of atoms in the ground level is greater than the remaining levels. But for laser action, we need more no. of atoms in the higher energy state. So, Laser is operated using Population Inversion. Population inversion is used to increase the probability of stimulated emission, to increase the no. of atoms in higher energy level. Amplification of the laser light is guaranteed because of Population Inversion. When population inversion is achieved, then the stimulated emission happens.

Note:The orientation of the atom depends more generally on the frequency, intensity, polarization, spectral bandwidth of the laser as well as the line width and transition probability of the absorbing transition.