Question

Explain the working of Ruby Laser with the help of an energy level diagram.

Answer 1

Step 1: Working on Ruby Laser

1. Ina laser when an electronic transition occurs from a higher energy state to a lower energy state, there is a stimulated emission of photons, which is known as the laser gain medium.
2. A ruby laser uses a crystal made up of synthetic ruby as its gain medium.
3. Since a ruby laser used a solid ruby crystal, it falls under a solid-state laser.
4. Light is completely reflected through the fully reflecting mirror.
5. Most part of the light is reflected from the partially reflecting mirror, but some of it is allowed to pass through it in order to produce an output.
6. The electromagnetic ray produced from a ruby laser is coherent visible light.
7. It uses a rod made up of ruby that has to be pumped to high energy.
8. This is done to achieve population inversion.

Step 2: Energy level Diagram

1. Let us consider three levels of energy $E_1,E_2,E_3$ with $N$ number of electrons where $E_1<E_2<E_3$.
2. $E_1$ is the ground state, $E_2$ is the metastable state, and $E_3$ is the high energy state.
3. Most electrons are initially in $E_1$ state and only a few electrons are present in the $E_2$ and $E_3$ state.
4. The electrons transfer energy in the $E_1$ state and to the $E_3$ state as the laser medium absorbs light energy, and the electrons start to gain energy.
5. The lifespan of the pump state $E_3$ is very short, and hence the electrons in the $E_3$ do not stay for a long time.
6. They fall into $E_2$ and hence release energy.
7. The lifespan of $E_2$ is much greater than that of $E_3$.
8. After a while, the electrons in $E_2$ fall into $E_1$.
9. As a consequence, photons are emitted which is called stimulated radiation emission.