Answer to Question #90071 in Optics for Shivam Nishad

Question

Explain the term population inversion. Why
is it necessary to have population inversion
for operation of a laser ? Draw a line diagram
showing three level pumping scheme.

Answer 1

Stimulated emission - an electron in a higher energy state interacts with a photon that stimulates it to return to a lower energy state, and a photon is released.

Population inversion occurs when more electrons, in a particular situation, are in a higher energy state than in a lower energy state. Population inversion can be thought of as an inversion from the standard, since electrons are typically located in lower energy states. The true power of population inversion comes from the fact that the input of a single photon can lead to an important end result. That is, all of the higher energy electrons will 'drop' to a lower energy state.